Boosting CO2 hydrogenation via size-dependent metal–support interactions in cobalt/ceria-based catalysts

Upcycling hazardous waste into high-performance Ni/η-Al2O3 catalysts for CO2 methanation

Transforming hazardous and difficult-to-process waste materials, like spent Ni-MH batteries and aluminium foil, into nanocatalysts (NCts) provides a sustainable solution for resource management and reducing environmental impact. This study demonstrates a novel approach by extracting nickel sulfate (NiSO4·xH2O) from battery waste and subsequently converting it into Ni(OH)2 hydrogel precursors using l-glutamic acid. Waste aluminium foil was processed into alumina (Al2O3), and combined with Ni(OH)2 to synthesize Ni/η-Al2O3 NCts with 4% and 8% Ni loading. Characterization through XRD/SAED, STEM/EFTEM, and EELS revealed a disordered cubic structure of η-Al2O3, with well-dispersed Ni particles, making it effective for CO2 hydrogenation. The 8-Ni/η-Al2O3 exhibited the best catalytic performance, with CH4 selectivity of 99.8% and space time yield (STY) of 80.3 mmolCH4 gcat -1 h-1 at 400 °C. The CO2 methanation mechanism over Ni/η-Al2O3 NCts was further explored using operando DRIFTS aligned with GC + MS. The operando investigation suggested a preferential associative CO2 methanation pathway, involving sequential adsorption and hydrogenation of CO2 to hydrogen carbonates on Ni/η-Al2O3, and their transformation into formate and methoxy intermediates leading to methane. Finally, to complete the upcycling/recycling loop, the spent Ni/η-Al2O3 NCts were recycled into Ni and Al precursors. These findings underscore the potential of upcycling waste materials for synthesizing sustainable, high-performance NCts, and offer insights into the CO2 methanation mechanism.

Interfacial Catalysis at Atomic Level

Heterogeneous catalysts are pivotal to the chemical and energy industries, which are central to a multitude of industrial processes. Large-scale industrial catalytic processes rely on special structures at the nano- or atomic level, where reactions proceed on the so-called active sites of heterogeneous catalysts. The complexity of these catalysts and active sites often lies in the interfacial regions where different components in the catalysts come into contact. Recent advances in synthetic methods, characterization technologies, and reaction kinetics studies have provided atomic-scale insights into these critical interfaces. Achieving atomic precision in interfacial engineering allows for the manipulation of electronic profiles, adsorption patterns, and surface motifs, deepening our understanding of reaction mechanisms at the atomic or molecular level. This mechanistic understanding is indispensable not only for fundamental scientific inquiry but also for the design of the next generation of highly efficient industrial catalysts. This review examines the latest developments in atomic-scale interfacial engineering, covering fundamental concepts, catalyst design, mechanistic insights, and characterization techniques, and shares our perspective on the future trajectory of this dynamic research field.

Oxygen Vacancies Promote Formaldehyde Base-Free Reforming into Hydrogen over Cu Doping-Induced Cu-CuxZn1-xO Heterointerfaces

Element doping is a viable strategy to regulate the metal-support interface for enhancing the catalytic performance of supported metal catalysts. Herein, Cu/ZnO:Cu-TH catalysts are prepared by immobilizing Cu nanoparticles (NPs) on ZnO nanorods featuring an adjustable oxygen vacancy, in which partial Cu atoms at the Cu-ZnO interface are incorporated into the ZnO lattice to form CuxZn1-xO species. Such Cu atom doping induces the creation of distinctive Cu-CuxZn1-xO interface sites and optimizes electron transfer from ZnO to Cu NPs, thereby achieving intermediate activation and ultimately endowing the catalyst with superior performance in reforming alkali-free formaldehyde (HCHO) into hydrogen at low temperatures. The Cu-CuxZn1-xO interface sites serve as pivotal centers for HCHO reforming, where the Cu sites and CuxZn1-xO sites selectively engage in the cleavage of C-H bonds in HCHO and O-H bonds in H2O, respectively. Meanwhile, the presence of oxygen vacancies bolsters the Cu-CuxZn1-xO sites in enhancing the adsorption of HCHO and H2O, further improving the activity. The Cu/ZnO:Cu-450H catalyst, distinguished by abundant Cu-CuxZn1-xO sites and a high concentration of oxygen vacancies, demonstrates optimal activity with TOF values of 16.9 and 72.4 h-1 under anaerobic and aerobic conditions, respectively, which are 8.9 and 29.0 times higher than those of the Cu/ZnO-450N catalyst, which lacks doped Cu atoms and oxygen vacancies.

Electronic metal-support interaction modulates Cu electronic structures for CO2 electroreduction to desired products

In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides (Al2O3-CuSAC, CeO2-CuSAC, and TiO2-CuSAC) are used as theoretical models to explore the correlations between electronic structures and CO2RR performances. For these catalysts, the electronic metal-support interaction (EMSI) induced by charge transfer between Cu sites and supports subtly modulates the Cu electronic structure to form different highest occupied-orbital. The highest occupied 3dyz orbital of Al2O3-CuSAC enhances the adsorption strength of CO and weakens C-O bonds through 3dyz-π* electron back-donation. This reduces the energy barrier for C-C coupling, thereby promoting multicarbon formation on Al2O3-CuSAC. The highest occupied 3dz2 orbital of TiO2-CuSAC accelerates the H2O activation, and lowers the reaction energy for forming CH4. This over activated H2O, in turn, intensifies competing hydrogen evolution reaction (HER), which hinders the high-selectivity production of CH4 on TiO2-CuSAC. CeO2-CuSAC with highest occupied 3dx2-y2 orbital promotes CO2 activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO2-CuSAC facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO2-CuSAC exhibits the highest CH4 Faradaic efficiency of 70.3% at 400 mA cm-2.

Epoxyethane Methoxycarbonylation over a Heterogeneous Catalyst Based on Functionalized Cobalt Carbonyl

In this work, we report a new heterogeneous catalyst for the methoxycarbonylation of epoxyethane (EO) to methyl 3-hydroxypropanoate (3-HPM), achieving good yields and recyclability of up to three times with no obvious loss in catalytic activity. The catalysts were prepared through an effective strategy to anchor active cobalt carbonyl species to functionalized silica-based molecular sieves. The successful grafting of functional ligand and cobalt carbonyl cluster was evident through 29Si-MAS NMR and FT-IR studies. Furthermore, an in situ FT-IR study indicates that a binuclear cobalt carbonyl catalyst may undergo a shift from bridged carbonyl to terminal carbonyl in the methoxycarbonylation of EO. According to time-dependent in situ FT-IR spectra in the carbonyl stretching region, the main product and intermediate are both captured, showing a new reaction mechanism different from the previous literature reports. These findings are significant for insight into the relation between the catalytic performance and structure.

A Scenario for a Carbon-Neutral Ammonia-Fueled Engine Mediated by Catalytic NH3 Cracking and CO2 Hydrogenation

Utilizing near zero-carbon NH3 as fuel in engines is promising for carbon-neutrality. However, the application of NH3 into the engine suffers from the intrinsic poor combustion characteristics of NH3 and the emission of harmful NOx exhausts. Herein, we proposed and successfully confirmed a novel scenario for converting a conventional "CH4-fueled" engine to "NH3-fueled" engine. Specifically, CH4 was used to power the internal combustion engine and release CO2 as the exhaust. Afterwards, we put forward two routes to convert the exhaust and NH3 into N2 and CH4 for enclosing the carbon cycle. The first "spatially decoupled" route splits the exhaust treatment into NH3 cracking over Ru clusters on the calcined Mg-Al hydrotalcite (Ru/MAO) and CO2 methanation over a commercial Ni/Al2O3. Both NH3 and CO2 were almost completely converted into the target products under their respective optimal conditions. The second "spatially coupled" route refers to an one-pot reaction of NH3 and CO2 into N2, CH4, and H2O. Due to the mismatch of reaction conditions and the competitive adsorption of reactants, the conversions of NH3 and CO2 were lowered to 80.1 % and 49.3 %, respectively, over Ru/MAO under 1 bar (CO2:NH3=3 : 8) at 550 °C.

Tuning the electronic structure and SMSI by integrating trimetallic sites with defective ceria for the CO2 reduction reaction

Heterogeneous catalysts have emerged as a potential key for closing the carbon cycle by converting carbon dioxide (CO2) into value-added chemicals. In this work, we report a highly active and stable ceria (CeO2)-based electronically tuned trimetallic catalyst for CO2 to CO conversion. A unique distribution of electron density between the defective ceria support and the trimetallic nanoparticles (of Ni, Cu, Zn) was established by creating the strong metal support interaction (SMSI) between them. The catalyst showed CO productivity of 49,279 mmol g-1 h-1 at 650 °C. CO selectivity up to 99% and excellent stability (rate remained unchanged even after 100 h) stemmed from the synergistic interactions among Ni-Cu-Zn sites and their SMSI with the defective ceria support. High-energy-resolution fluorescence-detection X-ray absorption spectroscopy (HERFD-XAS) confirmed this SMSI, further corroborated by in situ electron energy loss spectroscopy (EELS) and density functional theory (DFT) simulations. The in situ studies (HERFD-XAS & EELS) indicated the key role of oxygen vacancies of defective CeO2 during catalysis. The in situ transmission electron microscopy (TEM) imaging under catalytic conditions visualized the movement and growth of active trimetallic sites, which completely stopped once SMSI was established. In situ FTIR (supported by DFT) provided a molecular-level understanding of the formation of various reaction intermediates and their conversion into products, which followed a complex coupling of direct dissociation and redox pathway assisted by hydrogen, simultaneously on different active sites. Thus, sophisticated manipulation of electronic properties of trimetallic sites and defect dynamics significantly enhanced catalytic performance during CO2 to CO conversion.

Single-Atom Barium Promoter Enormously Enhanced Non-Noble Metal Catalyst for Ammonia Decomposition

As a well-established topic, single-atom catalyst has drawn growing interest for its high utilization of metal. However, researchers prefer to develop various active metals with single-atom form, the intrinsic roles of single-atom promoters are usually underrated, which are significant in boosting reaction activity. In this work, Ba single atoms were in situ prepared in the Co-Ba/Y2O3 catalyst with crystallized BaCO3 as the precursor under the ammonia decomposition reaction condition. The optimized Co-Ba/Y2O3 catalyst achieves extremely high H2 production rate of 138.3 mmolH2 ⋅ gcat -1 ⋅ min-1 at very low temperature (500 °C, GHSV=840,000 mL ⋅ g-1 ⋅ h-1) and Co-Ba/Y2O3 exhibits excellent durability during the 350 h test, which realizes the highest activity among all non-noble catalysts, and reaches or even exceeds numerous reported Ru-based catalysts. Both Y2O3 and Co demonstrate positive interactions with Ba, which significantly facilitates the dispersion of Ba species at high temperatures (≥600 °C). Ba single atoms significantly enhance the charge density of Co and form additionally active Co-O-Ba-Y2O3 interfacial sites, which alleviates hydrogen poisoning and decreases the reaction barrier of the N-H bond activation of *NH. The exploration of atomically dispersed promoters is groundbreaking in heterogeneous catalysis, which opens up a whole new domain of catalytic material.

Partial PdAu nanoparticle embedding into TiO2 support accentuates catalytic contributions from the Au/TiO2 interface

Despite the broad catalytic relevance of metal-support interfaces, controlling their chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently, their contributions to overall catalytic reactivity, remains challenging, as the nanoparticle and support characteristics are interdependent when catalysts are prepared by impregnation. Here, we decoupled both characteristics by using a raspberry-colloid-templating strategy that yields partially embedded PdAu nanoparticles within well-defined SiO2 or TiO2 supports, thereby increasing the metal-support interfacial contact compared to nonembedded catalysts that we prepared by attaching the same nanoparticles onto support surfaces. Between nonembedded PdAu/SiO2 and PdAu/TiO2, we identified a support effect resulting in a 1.4-fold higher activity of PdAu/TiO2 than PdAu/SiO2 for benzaldehyde hydrogenation. Notably, partial nanoparticle embedding in the TiO2 raspberry-colloid-templated support increased the metal-support interfacial perimeter and consequently, the number of Au/TiO2 interfacial sites by 5.4-fold, which further enhanced the activity of PdAu/TiO2 by an additional 4.1-fold. Theoretical calculations and in situ surface-sensitive desorption analyses reveal facile benzaldehyde binding at the Au/TiO2 interface and at Pd ensembles on the nanoparticle surface, explaining the connection between the number of Au/TiO2 interfacial sites (via the metal-support interfacial perimeter) and catalytic activity. Our results demonstrate partial nanoparticle embedding as a synthetic strategy to produce thermocatalytically stable catalysts and increase the number of catalytically active Au/TiO2 interfacial sites to augment catalytic contributions arising from metal-support interfaces.

Ru-OH-Zr Site over Metal-Organic Frameworks Boosts Coreactant Activation for Efficient Electrochemiluminescence

Metal-organic frameworks (MOFs) are promising electrochemiluminescent (ECL) nanoemitters. Great endeavors have been made to optimize the inherent luminescent properties, yet most MOFs suffer from poor coreactant activation ability, resulting in limited ECL. Therefore, it is urgent to integrate and design efficient catalytic centers within MOFs. Herein, we decorate atomically dispersed Ru onto the Zr-nodes of NU-1000, constructing Ru-OH-Zr centers to synergistically activate coreactants. The proposed NU-Ru enables 7.8 times enhancement in ECL efficiency. Theoretical investigations reveal that Ru atoms with strong electronegativity not only accelerate the charge transfer but also provide superior Lewis acid sites for promoting peroxysulfate binding and activation. Assisted by Bro̷nsted acid groups, the Ru-OH-Zr centers efficiently split the O-O bonds to enrich radicals through a proton-coupled electron transfer process. Furthermore, a direct mode sensor was established for sensitive organophosphorus pesticide analysis based on the interaction between the P═O bond and Lewis acid sites.

Monolayer Amphiphiles Hydrophobicize MoS2-Mediated Real-Time Water Removal for Efficient Waterproof Hydrogen Detection

Ensuring water-fouling-free operation of semiconductor-based gas sensors is essential to maintaining their accuracy, reliability, and stability across diverse applications. Despite the use of hydrophobic strategies to prevent external water intrusion, addressing in situ-produced water transport during H2 detection remains a challenge. Herein, we construct a novel waterproof H2 sensor by integrating single-atom Ru(III) self-assembly with monolayer amphiphiles embedded in MoS2. The unique monolayer structure enables the sensor to detect H2 in the presence of water, as well as facilitate the self-transport of in situ-generated water from the H2-O2 reaction during H2 detection. Molecular dynamics simulations reveal that monolayer amphiphiles exhibit a higher water diffusion coefficient than multilayer amphiphiles, making them more advantageous for removing in situ-produced water. Deployable on mobile platforms, it enables wireless H2cat detection for up to 6 months, without the introduction of protective membranes against dust and water ingress. This work not only enhances the performance of H2 detection but also introduces a new concept for the advancement of stable water-sensitive sensors.

Rational H2 Partial Pressure over Nickel/Ceria Crystal Enables Efficient and Durable Wide-Temperature-Zone Air-Level CO2 Methanation

On the way to carbon neutrality, directly catalyzing atmospheric CO2 into high-value chemicals might be an effective approach to mitigate the negative impacts of rising airborne CO2 concentrations. Here, we pioneer the investigation of the influence of the H2/CO2 partial pressure ratio (PPR) on air-level CO2 methanation. Using Ni/CeO2 as a case catalyst, increasing H2/CO2 PPR significantly improves low-temperature CO2 conversion and high-temperature CH4 selectivity, i. e., from 10 of H2/CO2 PPR on, CO2 is completely methanized at 250 °C, and nearly 100 % CH4 selectivity is achieved at 400 °C. 100-hour stability tests demonstrate the practical application potential of Ni/CeO2 at 250 °C and 400 °C. In-situ DRIFTS reveal that reinforced formate pathway by increasing H2/CO2 PPR is responsible for the high CH4 yield. In contrast, even though the CO pathway dominated CO2 conversion on Ni is enhanced by rising H2/CO2 PPR, but at a high reaction temperature, the promoted CO desorption still leads to lower CH4 selectivity. This work offers deep insights into the direct air-level CO2 resourceization, contributing to the achievement of airborne CO2 reductions.

Ce Promotion of In2O3 for Electrochemical Reduction of CO2 to Formate

In2O3 is a promising electrocatalyst for CO2 electroreduction (CO2ER) to formate. In2O3 nanoparticles doped with Pd, Ni, Co, Zr, and Ce promoters using flame-spray pyrolysis were characterized and evaluated in a gas diffusion electrode for the CO2ER. Doping results in slight shifts of the In binding energy as probed by XPS, which correlates with a change of the Faradaic efficiency to formate (FEformate) in the order Ce-doped In2O3 > Zr-doped In2O3 > In2O3 > Pd-doped In2O3 > Ni-doped In2O3 > Co-doped In2O3. However, the differences in CO2ER performance are caused mainly by the different extent of In2O3 reduction. Co-doped In2O3 is prone to complete reduction to a stable Co-In alloy with a low FEformate due to a high hydrogen evolution activity. The stabilizing effect of Ce on In2O3 is further demonstrated by an X-ray absorption spectroscopy study of a set of Ce-doped In2O3 samples (10, 50, 90 at%), highlighting that reduction of In2O3 is suppressed with increasing Ce content. Optimum performance in terms of FEformate is obtained at a Ce content of 10 at%, which is attributed to the stabilization of In2O3 under negative bias up to -2 V. At higher Ce content, less active CeO2 is formed. The highest FEformate of 86% observed for In2O3 doped with 10 at% Ce, at a current density of 150 mA/cm2, compares favorably with a FEformate of 78% for In2O3.

Palladium-assisted NOx storage and release on CexZr1-xO2 for passive NOx adsorber in diesel exhaust aftertreatment

Understanding Pd effects on NOx storage and release is crucial for designing passive NOx adsorber (PNA) to control NOx emissions during diesel cold-starts. Herein, we report two oxidation states of Pd species on CexZr1-xO2 regulated by metal-support interaction. Pdδ+ (0 < δ < 2) in Pd/Ce0.25Zr0.75O2 exhibits a high affinity for O2 adsorption, which promotes the oxidation of adsorbed NO to nitrates at 100 °C. These nitrates are thermally unstable due to electron transfer from the Pd atom to the N-O bond, facilitating the decomposition of nitrates to NO2 above 200 °C. In contrast, Pd2+ in Pd/Ce0.75Zr0.25O2 prefer to NO adsorption. A large amount of adsorbed NO and nitrites accumulate on Pd2+ and Ce4+ results in high levels of NO release below 200 °C. For the potential application in PNA, Pd/Ce0.25Zr0.75O2 is recommended due to its proper NOx release temperature as well as better water and SO2 resistance.

Electron-donable heterojunctions with synergetic Ru-Cu pair sites for biocatalytic microenvironment modulations in inflammatory mandible defects

The clinical treatments of maxillofacial bone defects pose significant challenges due to complex microenvironments, including severe inflammation, high levels of reactive oxygen species (ROS), and potential bacterial infection. Herein, we propose the de novo design of an efficient, versatile, and precise electron-donable heterojunction with synergetic Ru-Cu pair sites (Ru-Cu/EDHJ) for superior biocatalytic regeneration of inflammatory mandible defects and pH-controlled antibacterial therapies. Our studies demonstrate that the unique structure of Ru-Cu/EDHJ enhances the electron density of Ru atoms and optimizes the binding strength of oxygen species, thus improving enzyme-like catalytic performance. Strikingly, this biocompatible Ru-Cu/EDHJ can efficiently switch between ROS scavenging in neutral media and ROS generation in acidic media, thus simultaneously exhibiting superior repair functions and bioadaptive antibacterial properties in treating mandible defects in male mice. We believe synthesizing such biocatalytic heterojunctions with exceptional enzyme-like capabilities will offer a promising pathway for engineering ROS biocatalytic materials to treat trauma, tumors, or infection-caused maxillofacial bone defects.

Strong metal-support interaction (SMSI) in environmental catalysis: Mechanisms, application, regulation strategies, and breakthroughs

The strong metal-support interaction (SMSI) in supported catalysts plays a dominant role in catalytic degradation, upgrading, and remanufacturing of environmental pollutants. Previous studies have shown that SMSI is crucial in supported catalysts' activity and stability. However, for redox reactions catalyzed in environmental catalysis, the enhancement mechanism of SMSI-induced oxygen vacancy and electron transfer needs to be clarified. Additionally, the precise control of SMSI interface sites remains to be fully understood. Here we provide a systematic review of SMSI's catalytic mechanisms and control strategies in purifying gaseous pollutants, treating organic wastewater, and valorizing biomass solid waste. We explore the adsorption and activation mechanisms of SMSI in redox reactions by examining interfacial electron transfer, interfacial oxygen vacancy, and interfacial acidic sites. Furthermore, we develop a precise regulation strategy of SMSI from systematical perspectives of interface effect, crystal facet effect, size effect, guest ion doping, and modification effect. Importantly, we point out the drawbacks and breakthrough directions for SMSI regulation in environmental catalysis, including partial encapsulation strategy, size optimization strategy, interface oxygen vacancy strategy, and multi-component strategy. This review article provides the potential applications of SMSI and offers guidance for its controlled regulation in environmental catalysis.

The Structure, Oxidation States, and Energetics of Co Nanoparticles on CeO2(111): An STM and DFT Study

Co nanoparticles (NPs) dispersed on ceria have been widely studied as active catalytic materials for many industrially relevant reactions. The detailed nature of such particles and the factors affecting their interaction with ceria remain to be better understood. In this study, a very low coverage (∼0.02 ML) of Co is deposited on a model CeO2(111) thin-film surface and is examined using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). The Co NPs that nucleate on terrace sites grow with coverage in this range to a maximum size of ca. 40 Co atoms, with an average diameter and height of 16.1 and 1.1 Å, respectively. Global minimization of the structures of Co NPs consisting of up to 23 Co atoms on CeO2(111) is performed based on the minima hopping algorithm and density functional theory (DFT) calculations, and the energetic and chemical properties of the resulting NPs are analyzed. While the theoretical findings are consistent with the STM observations on the strong Co-ceria interactions and the prevalence of oxidic Co species, some notable discrepancies are identified, including inconsistent aspect ratios and the existence of a low oxidation state Coδ+ species. The combined experimental and theoretical findings provide new insights into Co NPs formed on ceria and identify areas requiring further investigation.

Metal-support interactions in metal oxide-supported atomic, cluster, and nanoparticle catalysis

Supported metal catalysts are essential to a plethora of processes in the chemical industry. The overall performance of these catalysts depends strongly on the interaction of adsorbates at the atomic level, which can be manipulated and controlled by the different constituents of the active material (i.e., support and active metal). The description of catalyst activity and the relationship between active constituent and the support, or metal-support interactions (MSI), in heterogeneous (thermo)catalysts is a complex phenomenon with multivariate (dependent and independent) contributions that are difficult to disentangle, both experimentally and theoretically. So-called "strong metal-support interactions" have been reported for several decades and summarized in excellent review articles. However, in recent years, there has been a proliferation of new findings related to atomically dispersed metal sites, metal oxide defects, and, for example, the generation and evolution of MSI under reaction conditions, which has led to the designation of (sub)classifications of MSI deserving to be critically and systematically evaluated. These include dynamic restructuring under alternating redox and reaction conditions, adsorbate-induced MSI, and evidence of strong interactions in oxide-supported metal oxide catalysts. Here, we review recent literature on MSI in oxide-supported metal particles to provide an up-to-date understanding of the underlying physicochemical principles that dominate the observed effects in supported metal atomic, cluster, and nanoparticle catalysts. Critical evaluation of different subclassifications of MSI is provided, along with discussions on the formation mechanisms, theoretical and characterization advances, and tuning strategies to manipulate catalytic reaction performance. We also provide a perspective on the future of the field, and we discuss the analysis of different MSI effects on catalysis quantitatively.

The support effect on the performance of a MOF-derived Co-based nano-catalyst in Fischer Tropsch synthesis

The catalyst plays a central role in the Fischer-Tropsch synthesis (FTS) process, and the choice of catalyst support significantly impacts FTS catalyst performance by enhancing its attributes. In this study, the effects of utilizing various metal oxides-CeO2, ZrO2, and TiO2-on a cobalt-based FTS nanocatalyst are investigated by evaluating the catalyst's reducibility, stability, syngas chemisorption, intermediate species spillover, charge transfer, and metal-support interaction (MSI). This evaluation is conducted both theoretically and experimentally through diverse characterization tests and molecular dynamics (MD) simulations. Characterization tests reveal that the ceria-supported catalyst (Ceria Nano Catalyst, CNC) demonstrates the highest reducibility, stability, CO chemisorption, and spillover, while the zirconia-supported catalyst (Zirconia Nano Catalyst, ZNC) exhibits the highest hydrogen chemisorption and spillover. The MD simulation results align well with these findings; for instance, ZNC has the lowest hydrogen adsorption enthalpy (ΔHAds.), whereas CNC has the lowest ΔHAds. for CO. Additionally, MD simulations indicate that the titania-supported catalyst (Titania Nano Catalyst, TNC) possesses the highest MSI value, closely resembling that of ZNC, albeit with a minor difference. The TNC catalyst's performance in other tests is also similar to that of ZNC. Finally, FTS performance tests illustrate that the ZNC catalyst achieves the highest CO conversion at 88.1%, while the CNC catalyst presents the lowest CO conversion at 82.2%. Notably, the CNC catalyst showcases the highest durability, with only a 4.4% loss in CO conversion and an 8.55% loss in C5+ yield after 192 h of operation.

Direct cleavage of C=O double bond in CO2 by the subnano MoOx surface on Mo2N

Compared to H2-assisted activation mode, the direct dissociation of CO2 into carbonyl (*CO) with a simplified reaction route is advantageous for CO2-related synthetic processes and catalyst upgrading, while the stable C = O double bond makes it very challenging. Herein, we construct a subnano MoO3 layer on the surface of Mo2N, which provides a dynamically changing surface of MoO3↔MoOx (x < 3) for catalyzing CO2 hydrogenation. Rich oxygen vacancies on the subnano MoOx surface with a high electron donating capacity served as a scissor to directly shear the C = O double bond of CO2 to form CO at a high rate. The O atoms leached in CO2 dissociation are removed timely by H2 to regenerate active oxygen vacancies. Owing to the greatly enhanced dissociative activation of CO2, this MoOx/Mo2N catalyst without any supported active metals shows excellent performance for catalyzing CO2 hydrogenation to CO. The construction of highly disordered defective surface on heterostructures paves a new pathway for molecule activation.

Strong Metal-Support Interaction Modulation between Pt Nanoclusters and Mn3O4 Nanosheets through Oxygen Vacancy Control to Achieve High Activities for Acidic Hydrogen Evolution

The optimization of metal-support interactions is used to fabricate noble metal-based nanoclusters with high activity for hydrogen evolution reaction (HER) in acid media. Specifically, the oxygen-defective Mn3O4 nanosheets supported Pt nanoclusters of ≈1.71 nm in diameter (Pt/V·-Mn3O4 NSs) are synthesized through the controlled solvothermal reaction. The Pt/V·-Mn3O4 NSs show a superior activity and excellent stability for the HER in the acidic media. They only require an overpotential of 19 mV to drive -10 mA cm-2 and show negligible activity loss at -10 and -250 mA cm-2 for >200 and >60 h, respectively. Their Pt mass activity is 12.4 times higher than that of the Pt/C and even higher than those of many single-atom based Pt catalysts. DFT calculations show that their high HER activity arises mainly from the strong metal-support interaction between Pt and Mn3O4. It can facilitate the charge transfer from Mn3O4 to Pt, optimizing the H adsorption on the catalyst surface and promoting the evolution of H2 through the Volmer-Tafel mechanism. The oxygen vacancies in the V·-Mn3O4 NSs are found to be inconducive to the high activity of the Pt/V·-Mn3O4 NSs, highlighting the great importance to reduce the vacancy levels in V·-Mn3O4 NSs.

Microfluidic Continuous Synthesis of Size- and Facet-Controlled Porous Bi2O3 Nanospheres for Efficient CO2 to Formate Catalysis

Bismuth-based catalysts are effective in converting carbon dioxide into formate via electrocatalysis. Precise control of the morphology, size, and facets of bismuth-based catalysts is crucial for achieving high selectivity and activity. In this work, an efficient, large-scale continuous production strategy is developed for achieving a porous nanospheres Bi2O3-FDCA material. First-principles simulations conducted in advance indicate that the Bi2O3 (111)/(200) facets help reduce the overpotential for formate production in electrocatalytic carbon dioxide reduction reaction (ECO2RR). Subsequently, using microfluidic technology and molecular control to precisely adjust the amount of 2, 5-furandicarboxylic acid, nanomaterials rich in (111)/(200) facets are successfully synthesized. Additionally, the morphology of the porous nanospheres significantly increases the adsorption capacity and active sites for carbon dioxide. These synergistic effects allow the porous Bi2O3-FDCA nanospheres to stably operate for 90 h in a flow cell at a current density of ≈250 mA cm- 2, with an average Faradaic efficiency for formate exceeding 90%. The approach of theoretically guided microfluidic technology for the large-scale synthesis of finely structured, efficient bismuth-based materials for ECO2RR may provide valuable references for the chemical engineering of intelligent nanocatalysts.

Support effect on Ni-based mono- and bimetallic catalysts in CO2 hydrogenation

Aiming at a comprehensive understanding of support effects on Ni-based bimetallic catalyst for CO2 hydrogenation, spectroscopy (DRIFTS) with CO as a probe molecule and temperature-programmed techniques were used to investigate the impact of different supports (MgO, CeO2, ZrO2) on Ni- and Ni,Fe catalysts. Kinetic parameters revealed that the higher selectivity to methanation for Ni and Ni,Fe supported on the reducible oxides (CeO2, ZrO2) is due to the inhibition of reverse water-gas shift reaction (RWGS) by hydrogen. A promoting effect of Fe on Ni was only observed on MgO-supported catalysts. In situ DRIFTS with CO adsorption showed different electronic properties of Ni sites with partially reduced oxide (i.e. ZrO2 and CeO2). H2-TPR and CO2-TPD confirmed the significant role of metal-support interaction (MSI) in CeO2-supported catalysts for CO2 activation. The MSI between Ni/Ni,Fe and reducible supports are crucial for catalytic performance, ultimately leading to the higher activity and stability in CO2 hydrogenation.

Tuning Catalytic Activity of CO2 Hydrogenation to C1 Product via Metal Support Interaction Over Metal/Metal Oxide Supported Catalysts

The metal supported catalysts are emerging catalysts that are receiving a lot of attention in CO2 hydrogenation to C1 products. Numerous experiments have demonstrated that the support (usually an oxide) is crucial for the catalytic performance. The support metal oxides are used to aid in the homogeneous dispersion of metal particles, prevent agglomeration, and control morphology owing to the metal support interaction (MSI). MSI can efficiently optimize the structural and electronic properties of catalysts and tune the conversion of key reaction intermediates involved in CO2 hydrogenation, thereby enhancing the catalytic performance. There is an increasing attention is being paid to the promotion effects in the catalytic CO2 hydrogenation process. However, a systematically understanding about the effects of MSI on CO2 hydrogenation to C1 products catalytic performance has not been fully studied yet due to the diversities in catalysts and reaction conditions. Hence, the characteristics and modes of MSI in CO2 hydrogenation to C1 products are elaborated in detail in our work.

Rapid construction of nickel phyllosilicate with ultrathin layers and high performance for CO2 methanation

The traditional techniques for the synthesis of nickel phyllosilicates usually time-consuming and energy-intensive, which often lead to the formation of layers with excessive thickness due to uncontrolled crystal growth. In order to overcome these challenges, this work introduces a microwave-assisted synthesis strategy to facilitate the synthesis of Ni-phyllosilicate-based catalysts within an exceptionally short duration of only five minutes, attaining a peak temperature of merely 102 °C. To enhance the specific surface area and to increase the exposure of active sites, an investigation was conducted involving three surfactants. The employment of hexadecyl trimethyl ammonium bromide (CTAB) has yielded remarkable results, with an ultrahigh specific surface area reaching 535 m2 g-1 and an ultrathin lamellar thickness of 1.43 nm. The catalyst exhibited an impressive CO2 conversion of 81.7 % at 400 °C, 60 L g-1 h-1, 0.1 MPa. It also demonstrated a substantial turnover frequency for CO2 (TOFCO2) of 5.4 ± 0.1 × 10-2 s-1, alongside a relatively low activation energy (Ea) of 80.74 kJ·mol-1. Moreover, the catalyst maintained its high stability over a period of 100 h and displayed high resistance to sintering. To further elucidate growth temperature gradient of the catalyst and concentration gradient of the materials involved, COMSOL Multiphysics (COMSOL) simulations were effectively utilized. In conclusion, this work breaks the limitation associated with traditional, laborious synthesis methods for Ni-phyllosilicates, which can produce materials with high surface area and thin-layer characteristics.

Visualizing Phase Evolution of Co2C for Efficient Fischer-Tropsch to Olefins

Cobalt carbide (Co2C) possesses high catalytic efficiency Fischer-Tropsch synthesis (FTS), while the products selectivity appears sensitive to crystallography geometry. Since the Anderson-Schulz-Flory (ASF) distribution in FTS is broken through fabricating facetted Co2C nanocrystals, yet the underlying mechanism of Co2C crystallization remains unclarified suffering from sophisticated catalyst composition involving promoter agents. Herein, the synthesis of high-purity single-crystal nanoprisms (Co2C-p) for highly efficient FTS is reported to lower olefins. Through comprehensive microstructure analysis, e.g., high-resolution TEM, in situ TEM and electron diffraction, as well as finite element simulation of gas flow field, for the first time the full roadmap of forming catalytic active cobalt carbides is disclosed, starting from reduction of Co3O4 precursor to CoO intermediate, then carburization into Co2C-s and subsequent ripening growth into Co2C-p. This gas-induced engineering of crystal phase provides a new synthesis strategy, with many new possibilities for precise design of metal-based catalyst for diverse catalytic applications.

Rationally designed Ru catalysts supported on TiN for highly efficient and stable hydrogen evolution in alkaline conditions

Electrocatalysis holds the key to enhancing the efficiency and cost-effectiveness of water splitting devices, thereby contributing to the advancement of hydrogen as a clean, sustainable energy carrier. This study focuses on the rational design of Ru nanoparticle catalysts supported on TiN (Ru NPs/TiN) for the hydrogen evolution reaction in alkaline conditions. The as designed catalysts exhibit a high mass activity of 20 A mg-1Ru at an overpotential of 63 mV and long-term stability, surpassing the present benchmarks for commercial electrolyzers. Structural analysis highlights the effective modification of the Ru nanoparticle properties by the TiN substrate, while density functional theory calculations indicate strong adhesion of Ru particles to TiN substrates and advantageous modulation of hydrogen adsorption energies via particle-support interactions. Finally, we assemble an anion exchange membrane electrolyzer using the Ru NPs/TiN as the hydrogen evolution reaction catalyst, which operates at 5 A cm-2 for more than 1000 h with negligible degradation, exceeding the performance requirements for commercial electrolyzers. Our findings contribute to the design of efficient catalysts for water splitting by exploiting particle-support interactions.

Tuning Adsorbate-Mediated Strong Metal-Support Interaction by Oxygen Vacancy: A Case Study in Ru/TiO2

The adsorbate-mediated strong metal-support interaction (A-SMSI) offers a reversible means of altering the selectivity of supported metal catalysts, thereby providing a powerful tool for facile modulation of catalytic performance. However, the fundamental understanding of A-SMSI remains inadequate and methods for tuning A-SMSI are still in their nascent stages, impeding its stabilization under reaction conditions. Here, we report that the initial concentration of oxygen vacancy in oxide supports plays a key role in tuning the A-SMSI between Ru nanoparticles and defected titania (TiO2-x). Based on this new understanding, we demonstrate the in situ formation of A-SMSI under reaction conditions, obviating the typically required CO2-rich pretreatment. The as-formed A-SMSI layer exhibits remarkable stability at various temperatures, enabling excellent activity, selectivity and long-term stability in catalyzing the reverse water gas-shift reaction. This study deepens the understanding of the A-SMSI and the ability to stabilize A-SMSI under reaction conditions represents a key step for practical catalytic applications.

Ultrafine Nanoclusters Unlocked 3d-4f Electronic Ladders for Efficient Electrocatalytic Water Oxidation

The vast extensional planes of two-dimensional (2D) nanomaterials are recognized as desirable ground for electrocatalytic reactions. However, they tend to exhibit catalytic inertia due to their surface-ordered coordination configurations. Herein, an in situ autoxidation strategy enables high-density grafting of ultrafine CeO2 nanoclusters on 2D Co(OH)2. Affluent active units were activated at the inert interface of Co(OH)2 via the formation of Co-O-Ce units. The optimized catalyst exhibits oxygen evolution reaction activity with an overpotential of 83 mV lower than that of Co(OH)2 at 10 mA cm-2. The cascade orbital coupling between Co (3d) and Ce (4f) in Co-O-Ce units drives electron transfer by unlocking a "d-f electron ladder". Meanwhile, the bond-order theorem analyses and the d-band center show that the occupancy of Co-3d-eg is optimized to balance the adsorption-desorption process of active sites to the key reaction intermediate *OOH, thereby making it easier to release oxygen. This work will drive the development of wider area electron modulation methods and provide guidance for the surface engineering of 2D nanomaterials.

Cobalt-Doped Ceria Sensitizer Effects on Metal Oxide Nanofibers: Heightened Surface Reactivity for High-Performing Chemiresistive Sensors

Chemiresistive gas sensors based on semiconducting metal oxides typically rely on noble metal catalysts to enhance their sensitivity and selectivity. However, noble metal catalysts have several drawbacks for practical utilization, including their high cost, their propensity for spontaneous agglomeration, and poisoning effects with certain types of gases. As such, in the interest of commercializing the chemiresistive gas sensor technology, we propose an alternative design for a noble-metal-free sensing material through the case study of Co-doped ceria (Co-CeO2) catalysts embedded in a SnO2 matrix. In this investigation, we utilized electrospinning and subsequent calcination to prepare Co-CeO2 catalyst nanoparticles integrated with SnO2 nanofibers (NFs) with uniform particle distribution and particle size regulation down to the sub-2 nm regime. The resulting Co-CeO2@SnO2 NFs exhibited superior gas sensing characteristics toward isoprene (C5H8) gas, a significant biomarker for monitoring the onset of various diseases through breath diagnostics. In particular, we identified that the Co-CeO2 catalysts, owing to the transition metal doping, facilitated the spillover of chemisorbed oxygen species to the SnO2 sensing body. This resulting in the sensor having a 27.4-fold higher response toward 5 ppm of C5H8 (compared to pristine SnO2), exceptionally high selectivity, and a low detection limit of 100 ppb. The sensor also exhibited high stability for prolonged response-recovery cycles, attesting to the strong anchoring of Co-CeO2 catalysts in the SnO2 matrix. Based on our findings, the transition metal-doped metal oxide catalysts, such as Co-CeO2, demonstrate strong potential to completely replace noble metal catalysts, thereby advancing the development of the commercially viable chemiresistive gas sensors free from noble metals, capable of detecting target gases at sub-ppm levels.

The nature of crystal facet effect of TiO2-supported Pd/Pt catalysts on selective hydrogenation of cinnamaldehyde: electron transfer process promoted by interfacial oxygen species

Supported noble metal nanocatalysts typically exhibit strong crystal plane dependent catalytic behavior, but their working mechanism is still unclear. Herein, using anatase TiO2 with well-exposed crystal facets of {101}, {100} and {001} as a prototype support, Pd- and Pt-based supported TiO2 nanocatalysts (TiO2-Pd and TiO2-Pt) were prepared by chemical reduction with NaBH4 as reducer, and they showed a distinct metal-dependent crystal facet effect in the selective hydrogenation of cinamaldehyde (CAL). For Pd-based nanocatalysts, most Pd species on the {100} plane of TiO2 are present in the oxidized form with positive charges and unexpectedly show higher reactivity than the Pd species in the zero-valence state on the {101} and {001} planes. On the contrary, Pt species on all three crystal planes of TiO2 show zero-valence state, with relatively low conversion, but much better selectivity for hydrogenation of a CO bond than Pd-based catalysts. Well-designed experiments manipulating the stability and type of surface oxygen species confirmed that the essence of the crystal facet effect of the catalyst support actually creates a unique nanoconfined interface at the molecular level to construct a surface p-band intermediate state (PBIS), which provides a new alternative channel for surface electron transfer and consequently accelerates the reaction kinetics.

Enrooted-Type Metal-Support Interaction Boosting Oxygen Evolution Reaction in Acidic Media

Supported metal catalysts with appropriate metal-support interactions (MSIs) hold a great promise for heterogeneous catalysis. However, ensuring tight immobilization of metal clusters/nanoparticles on the support while maximizing the exposure of surface active sites remains a huge challenge. Herein, we report an Ir/WO3 catalyst with a new enrooted-type MSI in which Ir clusters are, unprecedentedly, atomically enrooted into the WO3 lattice. The enrooted Ir atoms decrease the electron density of the constructed interface compared to the adhered (root-free) type, thereby achieving appropriate adsorption toward oxygen intermediates, ultimately leading to high activity and stability for oxygen evolution in acidic media. Importantly, this work provides a new enrooted-type supported metal catalyst, which endows suitable MSI and maximizes the exposure of surface active sites in contrast to the conventional adhered, embedded, and encapsulated types.

Redispersing Ir Nanoparticles via a Carbon-Assisted Pyrolysis Process to Break the Activity-Stability Trade-Off of H2 Sensors

Oxide semiconductor-supported metal nanoparticles often suffer from a high-temperature gas sensing process, resulting in agglomeration and coalescence, which significantly decrease their surface activity and stability. Here, we develop an in situ pyrolysis strategy to redisperse commercial Ir particles (∼15.6 nm) into monodisperse Ir species (∼5.4 nm) on ZnO supports, exhibiting excellent sintering-resistant properties and H2 sensing. We find that large-size Ir nanoparticles can undergo an unexpected splitting decomposition process and spontaneously migrate along the encapsulated carbon layer surface during high-temperature pyrolysis of ZIF-8. This resultant monodisperse status can be integrally reserved, accompanying further oxidation sintering. The final Irred/ZnO-450-based sensor exhibits outstanding stability, H2 response (10-2000 ppm), fast response/recovery capability (7/9.7 s@100 ppm), and good moisture resistance. In situ Raman and ex situ XPS further experimentally verify that highly dispersive Ir species can promote the electron transfer process during the gas sensing process. Our strategy thus provides important insights into the design of agglomeration-resistant gas sensing materials for highly effective H2 detection.

Metal-support spin orders: Crucial effect on electrocatalytic oxygen reduction

Magnetic property (e.g. spin order) of support is of great importance in the rational design of heterogeneous catalysts. Herein, we have taken the Ni-supported ferromagnetic (FM) CrBr3 support (Nix/CrBr3) to thoroughly investigate the effect of spin-order on electrocatalytic oxygen reduction reaction (ORR) via spin-polarized density functional theory calculations. Specifically, Ni loading induces anti-FM coupling in Ni-Cr, leading to a transition from FM-to-ferrimagnetic (FIM) properties, while Ni-Ni metallic bonds create a robust FM direct exchange, benefiting the improvement of the phase transition temperature. Interestingly, with the increase in Ni loading, the easy magnetic axis changes from out-of-plane (2D-Heisenberg) to in-plane (2D-XY). The adsorption properties of Nix/CrBr3, involving O2 adsorption energy and configuration, are not governed by the d-band center but strongly correlate with magnetic anisotropy. It is noteworthy that the applied potential and electrolyte acidity triggers spin-order transition phenomena during the ORR and induces the catalytic pathway change from 4e- ORR to 2e- ORR with the excellent onset potential of 0.93 V/reversible hydrogen electrode, comparable to the existing most excellent noble-metal catalysts. Generally, these findings offer new avenues to understand and design heterogeneous catalysts with magnetic support.

Concentrated solar CO2 reduction in H2O vapour with >1% energy conversion efficiency

H2O dissociation plays a crucial role in solar-driven catalytic CO2 methanation, demanding high temperature even for solar-to-chemical conversion efficiencies <1% with modest product selectivity. Herein, we report an oxygen-vacancy (Vo) rich CeO2 catalyst with single-atom Ni anchored around its surface Vo sites by replacing Ce atoms to promote H2O dissociation and achieve effective photothermal CO2 reduction under concentrated light irradiation. The high photon flux reduces the apparent activation energy for CH4 production and prevents Vo from depletion. The defects coordinated with single-atom Ni, significantly promote the capture of charges and local phonons at the Ni d-impurity orbitals, thereby inducing more effective H2O activation. The catalyst presents a CH4 yield of 192.75 µmol/cm2/h, with a solar-to-chemical efficiency of 1.14% and a selectivity ~100%. The mechanistic insights uncovered in this study should help further the development of H2O-activating catalysts for CO2 reduction and thereby expedite the practical utilization of solar-to-chemical technologies.

Synergy of a CuO/C3N4 interface and CuO nanoparticles in the ethynylation of formaldehyde for 1,4-butynediol synthesis

Catalysts made of CuO/Bi2O3 nanoparticles supported on g-C3N4 were synthesized using a MOF-derived strategy. The activation of CuO to CuCCCu species and stabilization of the catalyst were facilitated by the synergistic effect of the CuO/C3N4 interface and CuO nanoparticles, resulting in enhanced catalytic efficacy in the ethynylation of formaldehyde.

Ni-Based Catalysts for CO2 Methanation: Exploring the Support Role in Structure-Activity Relationships

The catalytic hydrogenation of CO2 to methane is one of the highly researched areas for the production of chemical fuels. The activity of catalyst is largely affected by support type and metal-support interaction deriving from the special method during catalyst preparation. Hence, we employed a simple solvothermal technique to synthesize Ni-based catalysts with different supports and studied the support role (CeO2, Al2O3, ZrO2, and La2O3) on structure-activity relationships in CO2 methanation. It is found that catalyst morphology can be altered by only changing the support precursors during synthesis, and therefore their catalytic behaviours were significantly affected. The Ni/Al2O3 with a core-shell morphology prepared herein exhibited a higher activity than the catalyst prepared with a common wet impregnation method. To have a comprehensive understanding for structure-activity relationships, advanced characterization (e. g., synchrotron radiation-based XAS and photoionization mass spectrometry) and in-situ diffuse reflectance infrared Fourier transform spectroscopy experiments were conducted. This research opens an avenue to further delve into the role of support on morphologies that can greatly enhance catalytic activity during CO2 methanation.

Facilitating the dry reforming of methane with interfacial synergistic catalysis in an Ir@CeO2-x catalyst

The dry reforming of methane provides an attractive route to convert greenhouse gases (CH4 and CO2) into valuable syngas, so as to resolve the carbon cycle and environmental issues. However, the development of high-performance catalysts remains a huge challenge. Herein, we report a 0.6% Ir/CeO2-x catalyst with a metal-support interface structure which exhibits high CH4 (~72%) and CO2 (~82%) conversion and a CH4 reaction rate of ~973 μmolCH4 gcat-1 s-1 which is stable over 100 h at 700 °C. The performance of the catalyst is close to the state-of-the-art in this area of research. A combination of in situ spectroscopic characterization and theoretical calculations highlight the importance of the interfacial structure as an intrinsic active center to facilitate the CH4 dissociation (the rate-determining step) and the CH2* oxidation to CH2O* without coke formation, which accounts for the long-term stability. The catalyst in this work has a potential application prospect in the field of high-value utilization of carbon resources.

Structural Heredity in Catalysis: CO2 Self-Selective CeO2 Nanocrystals for Efficient Photothermal CO2 Hydrogenation to Methane

The chemical inertness of CO2 molecules makes their adsorption and activation on a catalyst surface one of the key challenges in recycling CO2 into chemical fuels. However, the traditional template synthesis and chemical modification strategies used to tackle this problem face severe structural collapse and modifier deactivation issues during the often-needed post-processing procedure. Herein, a CO2 self-selective hydrothermal growth strategy is proposed for the synthesis of CeO2 octahedral nanocrystals that participate in strong physicochemical interactions with CO2 molecules. The intense affinity for CO2 molecules persists during successive high-temperature treatments required for Ni deposition. This demonstrates the excellent structural heredity of the CO2 self-selective CeO2 nanocrystals, which leads to an outstanding photothermal CH4 productivity exceeding 9 mmol h-1 mcat -2 and an impressive selectivity of >99%. The excellent performance is correlated with the abundant oxygen vacancies and hydroxyl species on the CeO2 surface, which create many frustrated Lewis-pair active sites, and the strong interaction between Ni and CeO2 that promotes the dissociation of H2 molecules and the spillover of H atoms, thereby greatly benefitting the photothermal CO2 methanation reaction. This self-selective hydrothermal growth strategy represents a new pathway for the development of effective catalysts for targeted chemical reactions.

Co/SiO2 Catalyst for Methoxycarbonylation of Acetylene: On Catalytic Performance and Active Species

Reppe carbonylation of acetylene is an atom-economic and non-petroleum approach to synthesize acrylic acid and acrylate esters, which are key intermediates in the textile, leather finishing, and polymer industries. In the present work, a noble metal-free Co@SiO2 catalyst was prepared and evaluated in the methoxycarbonylation reaction of acetylene. It was discovered that pretreatment of the catalyst by different reductants (i.e., C2H2, CO, H2, and syngas) greatly improved the catalytic activity, of which Co/SiO2-H2 demonstrated the best performance under conditions of 160 °C, 0.05 MPa C2H2, 4 MPa CO, and 1 h, affording a production rate of 4.38 gMA+MP gcat-1 h-1 for methyl acrylate (MA) and methyl propionate (MP) and 0.91 gDMS gcat-1 h-1 for dimethyl succinate (DMS), respectively. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and diffuse reflectance infrared Fourier transform spectra of CO adsorption (CO-DRIFTS) measurements revealed that an H2 reduction decreased the size of the Co nanoparticles and promoted the formation of hollow architectures, leading to an increase in the metal surface area and CO adsorption on the catalyst. The hot filtration experiment confirmed that Co2(CO)8 was generated in situ during the reaction or at the pre-activation stage, which served as the genuine active species. Our work provides a facile and convenient approach to the in situ synthetization of Co2(CO)8 for a Reppe carbonylation reaction.

Abundance of Low-Energy Oxygen Vacancy Pairs Dictates the Catalytic Performance of Cerium-Stabilized Zirconia

Cerium-stabilized zirconia (Ce1-xZrxOy, CZO) is renowned for its superior oxygen storage capacity (OSC), a key property long believed to be beneficial to catalytic oxidation reactions. However, 50% Ce-containing CZO recorded with the highest OSC has disappointingly poor performance in catalytic oxidation reactions compared to those with higher Ce contents but lower OSC ability. Here, we employ global neural network (G-NN)-based potential energy surface exploration methods to establish the first ternary phase diagram for bulk structures of CZO, which identifies three critical compositions of CZO, namely, 50, 60, and 80% Ce-containing CZO that are thermodynamically stable under typical synthetic conditions. 50% Ce-containing CZO, although having the highest OSC, exhibits the lowest O vacancy (Ov) diffusion rate. By contrast, 60% Ce-containing CZO, despite lower OSC (33.3% OSC compared to that of 50% Ce-containing CZO), reaches the highest Ov diffusion ability and thus offers the highest CO oxidation catalytic performance. The physical origin of the high performance of 60% Ce-containing CZO is the abundance of energetically favorable Ov pairs along the ⟨110⟩ direction, which reduces the energy barrier of Ov diffusion in the bulk and promotes O2 activation on the surface. Our results clarify the long-standing puzzles on CZO and point out that 60% Ce-containing CZO is the most desirable composition for typical CZO applications.

Structured Catalysts and Catalytic Processes: Transport and Reaction Perspectives

The structure of catalysts determines the performance of catalytic processes. Intrinsically, the electronic and geometric structures influence the interaction between active species and the surface of the catalyst, which subsequently regulates the adsorption, reaction, and desorption behaviors. In recent decades, the development of catalysts with complex structures, including bulk, interfacial, encapsulated, and atomically dispersed structures, can potentially affect the electronic and geometric structures of catalysts and lead to further control of the transport and reaction of molecules. This review describes comprehensive understandings on the influence of electronic and geometric properties and complex catalyst structures on the performance of relevant heterogeneous catalytic processes, especially for the transport and reaction over structured catalysts for the conversions of light alkanes and small molecules. The recent research progress of the electronic and geometric properties over the active sites, specifically for theoretical descriptors developed in the recent decades, is discussed at the atomic level. The designs and properties of catalysts with specific structures are summarized. The transport phenomena and reactions over structured catalysts for the conversions of light alkanes and small molecules are analyzed. At the end of this review, we present our perspectives on the challenges for the further development of structured catalysts and heterogeneous catalytic processes.

Stable Interfacial Ruthenium Species for Highly Efficient Polyolefin Upcycling

The present polyolefin hydrogenolysis recycling cases acknowledge that zerovalent Ru exhibits high catalytic activity. A pivotal rationale behind this assertion lies in the propensity of the majority of Ru species to undergo reduction to zerovalent Ru within the hydrogenolysis milieu. Nonetheless, the suitability of zerovalent Ru as an optimal structural configuration for accommodating multiple elementary reactions remains ambiguous. Here, we have constructed stable Ru0-Ruδ+ complex species, even under reaction conditions, through surface ligand engineering of commercially available Ru/C catalysts. Our findings unequivocally demonstrate that surface-ligated Ru species can be stabilized in the form of a Ruδ+ state, which, in turn, engenders a perturbation of the σ bond electron distribution within the polyolefin carbon chain, ultimately boosting the rate-determining step of C-C scission. The optimized catalysts reach a solid conversion rate of 609 g·gRu-1·h-1 for polyethylene. This achievement represents a 4.18-fold enhancement relative to the pristine Ru/C catalyst while concurrently preserving a remarkable 94% selectivity toward valued liquid alkanes. Of utmost significance, this surface ligand engineering can be extended to the gentle mixing of catalysts in ligand solution at room temperature, thus rendering it amenable for swift integration into industrial processes involving polyolefin degradation.

Disclosing Support-Size-Dependent Effect on Ambient Light-Driven Photothermal CO2 Hydrogenation over Nickel/Titanium Dioxide

The size of support in heterogeneous catalysts can strongly affect the catalytic property but is rarely explored in light-driven catalysis. Herein, we demonstrate the size of TiO2 support governs the selectivity in photothermal CO2 hydrogenation by tuning the metal-support interactions (MSI). Small-size TiO2 loading nickel (Ni/TiO2 -25) with enhanced MSI promotes photo-induced electrons of TiO2 migrating to Ni nanoparticles, thus favoring the H2 cleavage and accelerating the CH4 formation (227.7 mmol g-1  h-1 ) under xenon light-induced temperature of 360 °C. Conversely, Ni/TiO2 -100 with large TiO2 prefers yielding CO (94.2 mmol g-1  h-1 ) due to weak MSI, inefficient charge separation, and inadequate supply of activated hydrogen. Under ambient solar irradiation, Ni/TiO2 -25 achieves the optimized CH4 rate (63.0 mmol g-1  h-1 ) with selectivity of 99.8 %, while Ni/TiO2 -100 exhibits the CO selectivity of 90.0 % with rate of 30.0 mmol g-1  h-1 . This work offers a novel approach to tailoring light-driven catalytic properties by support size effect.

Supra-Photothermal CO2 Methanation over Greenhouse-Like Plasmonic Superstructures of Ultrasmall Cobalt Nanoparticles

Improving the solar-to-thermal energy conversion efficiency of photothermal nanomaterials at no expense of other physicochemical properties, e.g., the catalytic reactivity of metal nanoparticles, is highly desired for diverse applications but remains a big challenge. Herein, a synergistic strategy is developed for enhanced photothermal conversion by a greenhouse-like plasmonic superstructure of 4 nm cobalt nanoparticles while maintaining their intrinsic catalytic reactivity. The silica shell plays a key role in retaining the plasmonic superstructures for efficient use of the full solar spectrum, and reducing the heat loss of cobalt nanoparticles via the nano-greenhouse effect. The optimized plasmonic superstructure catalyst exhibits supra-photothermal CO2 methanation performance with a record-high rate of 2.3 mol gCo -1 h-1 , close to 100% CH4 selectivity, and desirable catalytic stability. This work reveals the great potential of nanoscale greenhouse effect in enhancing photothermal conversions through the combination with conventional promoting strategies, shedding light on the design of efficient photothermal nanomaterials for demanding applications.

Dynamic Behavior of Platinum Atoms and Clusters in the Native Oxide Layer of Aluminum Nanocrystals

Strong metal-support interactions (SMSIs) are well-known in the field of heterogeneous catalysis to induce the encapsulation of platinum (Pt) group metals by oxide supports through high temperature H2 reduction. However, demonstrations of SMSI overlayers have largely been limited to reducible oxides, such as TiO2 and Nb2O5. Here, we show that the amorphous native surface oxide of plasmonic aluminum nanocrystals (AlNCs) exhibits SMSI-induced encapsulation of Pt following reduction in H2 in a Pt structure dependent manner. Reductive treatment in H2 at 300 °C induces the formation of an AlOx SMSI overlayer on Pt clusters, leaving Pt single-atom sites (Ptiso) exposed available for catalysis. The remaining exposed Ptiso species possess a more uniform local coordination environment than has been observed on other forms of Al2O3, suggesting that the AlOx native oxide of AlNCs presents well-defined anchoring sites for individual Pt atoms. This observation extends our understanding of SMSIs by providing evidence that H2-induced encapsulation can occur for a wider variety of materials and should stimulate expanded studies of this effect to include nonreducible oxides with oxygen defects and the presence of disorder. It also suggests that the single-atom sites created in this manner, when combined with the plasmonic properties of the Al nanocrystal core, may allow for site-specific single-atom plasmonic photocatalysis, providing dynamic control over the light-driven reactivity in these systems.

Novel heterogeneous Fe-based catalysts for carbon dioxide hydrogenation to long chain α-olefins-A review

The thermocatalytic conversion of carbon dioxide (CO2) into high value-added chemicals provides a strategy to address the environmental problems caused by excessive carbon emissions and the sustainable production of chemicals. Significant progress has been made in the CO2 hydrogenation to long chain α-olefins, but controlling C-O activation and C-C coupling remains a great challenge. This review focuses on the recent advances in catalyst design concepts for the synthesis of long chain α-olefins from CO2 hydrogenation. We have systematically summarized and analyzed the ingenious design of catalysts, reaction mechanisms, the interaction between active sites and supports, structure-activity relationship, influence of reaction process parameters on catalyst performance, and catalyst stability, as well as the regeneration methods. Meanwhile, the challenges in the development of the long chain α-olefins synthesis from CO2 hydrogenation are proposed, and the future development opportunities are prospected. The aim of this review is to provide a comprehensive perspective on long chain α-olefins synthesis from CO2 hydrogenation to inspire the invention of novel catalysts and accelerate the development of this process.

Atomically synergistic Zn-Cr catalyst for iso-stoichiometric co-conversion of ethane and CO2 to ethylene and CO

Developing atomically synergistic bifunctional catalysts relies on the creation of colocalized active atoms to facilitate distinct elementary steps in catalytic cycles. Herein, we show that the atomically-synergistic binuclear-site catalyst (ABC) consisting of [Formula: see text]-O-Cr6+ on zeolite SSZ-13 displays unique catalytic properties for iso-stoichiometric co-conversion of ethane and CO2. Ethylene selectivity and utilization of converted CO2 can reach 100 % and 99.0% under 500  °C at ethane conversion of 9.6%, respectively. In-situ/ex-situ spectroscopic studies and DFT calculations reveal atomic synergies between acidic Zn and redox Cr sites. [Formula: see text] ([Formula: see text]) sites facilitate β-C-H bond cleavage in ethane and the formation of Zn-Hδ- hydride, thereby the enhanced basicity promotes CO2 adsorption/activation and prevents ethane C-C bond scission. The redox Cr site accelerates CO2 dissociation by replenishing lattice oxygen and facilitates H2O formation/desorption. This study presents the advantages of the ABC concept, paving the way for the rational design of novel advanced catalysts.

Low-temperature methanation of fermentation gas with Ni-based catalysts in a multicomponent system

A large amount of greenhouse gases, such as carbon dioxide and methane, are released during the production process of bioethanol and biogas. Converting CO2 into methane is a promising way of capturing CO2 and generating high-value gas. At present, CO2 methanation technology is still in the early stage. It requires high temperature (300-400 ℃) and pressure (> 1 MPa), leading to high cost and energy consumption. In this study, a new catalyst, Ni-Fe/Al-Ti, was developed. Compared with the activity of the common Ni/Al2O3 catalyst, that of the new catalyst was increased by 1/3, and its activation temperature was reduced by 100℃. The selectivity of methane was increased to 99%. In the experiment using simulated fermentation gas, the catalyst showed good catalytic activity and durability at a low temperature and atmospheric pressure. Based on the characterization of catalysts and the study of reaction mechanisms, this article innovatively proposed a Ni-Fe/Al-Ti quaternary catalytic system. Catalytic process was realized through the synergism of Al-Ti composite support and Ni-Fe promotion. The oxygen vacancies on the surface of the composite carrier and the higher activity metals and alloys promoted by Fe accelerate the capture and reduction of CO2. Compared with the existing catalysts, the new Ni-Fe/Al-Ti catalyst can significantly improve the methanation efficiency and has great practical application potential.

Photocatalytic ethylene production by oxidative dehydrogenation of ethane with dioxygen on ZnO-supported PdZn intermetallic nanoparticles

The selective oxidative dehydrogenation of ethane (ODHE) is attracting increasing attention as a method for ethylene production. Typically, thermocatalysts operating at high temperatures are needed for C-H activation in ethane. In this study, we describe a low temperature ( < 140 °C) photocatalytic route for ODHE, using O2 as the oxidant. A photocatalyst containing PdZn intermetallic nanoparticles supported on ZnO is prepared, affording an ethylene production rate of 46.4 mmol g-1 h-1 with 92.6% ethylene selectivity under 365 nm irradiation. When we employ a simulated shale gas feed, the photocatalytic ODHE system achieves nearly 20% ethane conversion while maintaining an ethylene selectivity of about 87%. The robust interface between the PdZn intermetallic nanoparticles and ZnO support plays a crucial role in ethane activation through a photo-assisted Mars-van Krevelen mechanism, followed by a rapid lattice oxygen replenishment to complete the reaction cycle. Our findings demonstrate that photocatalytic ODHE is a promising method for alkane-to-alkene conversions under mild conditions.