Highly Stable Pt/CeO2 Catalyst with Embedding Structure toward Water-Gas Shift Reaction

Finely Tailoring Metal-Support Interactions via Transient High-Temperature Pulses

Metal-support interactions (MSI) play a crucial role in enhancing the catalytic activity and stability of metal catalysts by establishing a stable metal-oxide interface. However, precisely controlling MSI at the atomic scale remains a significant challenge, as how to construct an optimal MSI is still not fully understood: Both insufficient and excessive MSI showed inferior catalytic performance. In this study, we propose finely tuning MSI using temporal-precise transient high-temperature pulse heating. Using Pt/CeO2 as a model system, we systematically investigate how variations in pulse duration and atmosphere influence the reconstruction of the metal-support interface and MSIs. This leads to the formation of two distinct types of MSI: (1) strong MSI (SMSI, Pt@CeO2) and (2) reactive MSI (RMSI, Pt5Ce@CeO2), each with unique compositions, structures, and electrochemical behaviors. Notably, Pt5Ce@CeO2 with RMSI exhibits remarkable catalytic performance in the alkaline hydrogen evolution, showing an overpotential of -29 mV and stable operation for over 300 h at -10 mA·cm-2. Theoretical studies reveal that alloying Pt with Ce to form Pt5Ce modifies the electronic structure of Pt, shifting the d-band center to optimize the adsorption and dissociation of intermediates, thereby reducing the reaction energy barrier. Moreover, the intimate interaction of Pt5Ce with CeO2 further improves the activity and stability. Our strategy enables precise, stepwise, and controllable regulation of MSIs, providing insights for the development of highly efficient and durable heterostructured catalysts with optimal MSI for a wide range of catalytic applications.

Dual effect of anchored sulphur and activated oxygen in the catalytic oxidation of organic sulfur over Pt single-atom catalysts

Foul-smelling organic sulfur gases removal of which is crucial for improving environmental quality and protecting human health. Herein, in this study, Pt single-atom (SA) loaded magnesium oxide (MgO) nanosheet catalysts were prepared, which exhibited the dual effects of anchored sulfur and activated oxygen that greatly enhanced the catalytic oxidation efficiency of methyl mercaptan (CH3SH), and 90 % complete oxidation of CH3SH could be achieved by Pt SA/MgO at 325 °C, with an oxidation efficiency that was 8 times higher than that of MgO nanosheets. A series of characterization results indicate that the valence state of Pt in the Pt SA/MgO catalyst ranges between 0 and +4, demonstrating its inherent electron-donating capability. Theoretical calculations show that the oxygen vacancy formation energy is reduced to 4.0 eV after the introduction of Pt SA, and the adsorption energy of atomic groups SH and CH3 is reduced to -1.5 and -2.0 eV. And the bond length of the MgO bond in Pt SA/MgO is shortened to 2.083 Å, forming an asymmetric structure with the PtO bond of 2.142 Å, effectively activating the lattice oxygen. Furthermore, A series of activity tests confirmed that the introduction of Pt SA reduced sulfate deposition, while the reaction pathway of CH3SH catalytic oxidation was optimised by changing the oxidation mechanism. The investigation offers a significant experimental foundation and novel viewpoints for the enhancement of high-performance catalytic oxidation catalysts targeting sulfur-containing volatile organic compounds (VOCs).

Insights from Modulation-Excitation Spectroscopy into the Role of Pt Geometrical Sites in the WGS Reaction

Modulation-excitation spectroscopy coupled to diffuse reflectance infrared Fourier transform spectroscopy (ME-DRIFTS) was explored in this work to obtain valuable insights into the structure-reactivity relations in nanostructured Pt catalysts for the water-gas shift (WGS) reaction. By using model Pt catalytic systems composed of colloidal Pt nanoparticles (NPs) deposited on CeO2 (i.e., reducible) and SiO2 (i.e., nonreducible) supports, it was possible to probe distinct Pt active sites and correlate them to the reaction intermediates and pathways. The analysis revealed that PtNPs/SiO2 favored the participation of well-coordinated (WC) and under-coordinated (UC) Pt sites in the reaction mechanism. In contrast, on PtNPs/CeO2/SiO2, the additional involvement of highly under-coordinated (HUC) Pt sites was also observed. Additionally, both fast and slow formate species were identified as active intermediates on the surface of the PtNPs/CeO2/SiO2 catalyst by ME-DRIFTS. More importantly, the faster reaction pathway was correlated to HUC and UC Pt sites, while the slower route was associated with WC Pt sites. Carbonates, on the other hand, were spectators. ME-DRIFTS experimentally demonstrate differences in the participation of Pt active sites according to the support, the involvement of interfacial sites, and the correlation of Pt local coordination to the surface intermediates in the WGS reaction.

Promoting Efficient Ruthenium Sites With Lewis Acid Oxide for the Accelerated Hydrogen and Chlor-Alkali Co-Production

Ruthenium (Ru) -based catalysts have been considered a promising candidate for efficient sustainable hydrogen and chlor-alkali co-production. Theoretical calculations have disclosed that the hollow sites on the Ru surface have strong adsorption energies of H and Cl species, which inevitably leads to poor activity for cathodic hydrogen evolution reaction (HER) and anodic chlorine evolution reaction (CER), respectively. Furthermore, it have confirmed that anchoring Lewis acid oxide nanoparticles such as MgO on the Ru surface can induce the formation of the onion-like charge distribution of Ru atoms around MgO nanoparticles, thereby exposing the Ru-bridge sites at the interface as excellent H and Cl adsorption sites to accelerate both HER and CER. Under the guidance of theoretical calculations, a novel dispersed MgO nanoparticles on Ru (MgOx-Ru) electrocatalyst is successfully prepared. In strongly alkaline and saline media, MgOx-Ru recorded excellent HER and CER electrocatalytic activity with a very low overpotential of 19 mV and 74 mV at the current density of 10 mA cm-2, respectively. More stirringly, the electrochemical test with MgOx-Ru as both anodic and cathodic electrodes under simulated chlor-alkali electrolysis conditions demonstrated superior electrocatalytic performance to the industrial catalysts of commercial 20 wt% Pt/C and dimensionally stable anode (DSA).

Ultrafine Nanoparticle Rh/CeO2-ZrO2 Catalysts Synthesized via Spatial Confinement: Higher Three-Way Catalytic Activity Compared to Rh Single-Atom Catalyst

The synthesis of size-controlled ultrafine metal-based catalysts is vitally important for chemical conversion technologies. This study presents a spatial confinement strategy for the synthesis of Rh/CeO2-ZrO2 (0.5 wt % Rh) three-way catalysts with ultrafine Rh nanoparticles (1-3 nm). This strategy utilizes the self-confinement effect of Rh ions through the strong electrostatic adsorption between Rh ions and the surface of CeO2-ZrO2, as well as the spatial hindrance provided by the mesopores of the support during Rh particle growth. The nanoparticle catalyst (NPC) with a size of ∼2.19 nm exhibits high catalytic performance, surpassing the Rh single-atom catalyst (SAC) and the other NPCs with different Rh sizes in the three-way catalytic reaction under a gas mixture of carbon monoxide (CO), hydrocarbons (HCs), and nitric oxide (NO). Rh SAC displays higher CO oxidation activity and comparable C3H6 oxidation activity compared with Rh NPC in reaction atmospheres without NO gas molecules. However, the presence of NO molecules hinders the adsorption and reaction of CO and HCs on the Rh single-atom sites. The impact of NO on Rh NPC is weaker due to the multiatomic active center structure of the Rh nanoparticles, resulting in enhanced low-temperature catalytic activity in three-way reaction atmospheres. Additionally, NPC demonstrates better stability than SAC under hydrothermal aging condition.

Anchoring Platinum Nanoparticles onto Oxygen Vacancy-Modified Mixed Metal Oxides for Selective Oxidation Reaction of Aromatic Alcohols

Directed transformation of organic compounds under mild conditions, especially alcohol oxidation, presents great challenges in green chemistry. Herein, we report a platinum nanoparticle catalyst supported on zinc-gallium mixed metal oxides (denoted as Pt/ZnGa-MMOs), which displays superior catalytic activity for the selective oxidation reaction of benzyl alcohol to benzaldehyde (conversion: >99%; selectivity: >99%; reaction rate: 125 mmolbenzyl alcohol gPt-1 h-1). Both experimental studies [X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure (XAFS)] and DFT calculations reveal the formation of an interfacial structure (Zn2+δ-Ov-Ga3-δ) on the ZnGa-MMOs support. Moreover, in situ Fourier transform infrared (FT-IR) spectroscopic analysis demonstrates that the Pt species acts as an intrinsic active center to promote the oxidation of the carbon-oxygen bond in the benzyl alcohol molecule, with the formation of the benzaldehyde. This work provides an effective strategy for the preparation of heterogeneous catalysts via constructing the support oxygen vacancy to anchor metal sites toward selective oxidation reactions.

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.

Hierarchical-Porous Hollow Nitrogen-Doped Carbon-Supported Pt Alloy Catalysts with a Controllable Triheterointerface for Methanol Electrooxidation

Carbon-supported Pt-based catalysts are the most effective catalysts for direct methanol fuel cells (DMFCs). However, challenges such as high Pt loading, cost, and susceptibility to CO poisoning severely hinder the development of DMFCs. In this paper, CoFe2O4@polymer@ZIF-67 is prepared successfully through sequential solution polymerization and in situ growth with modified CoFe2O4 as the core. Subsequently, a hierarchical-porous hollow nitrogen-doped carbon-confined controllable triheterointerface catalyst, PtCoFe-CoFeOx@N-HHCS, was successfully prepared via a strategy involving high-temperature-induced phase migration and in situ chemical replacement. Under the optimal conditions, the mass activity of PtCoFe-CoFeOx@N-HHCS reached 1054 mA mgPt-1, which is 4.1 and 2.1 times higher than those of commercial Pt/C and commercial PtRu/C, respectively. The peak potential of the CO electrooxidation of the PtCoFe-CoFeOx@N-HHCS shifts negatively by 70 mV compared with commercial Pt/C. The high methanol oxidation performance is attributed to the highly dispersed triheterointerface, hierarchical-porous hollow structure, and nitrogen-doped ultrathin carbon layer. The highly dispersed triheterointerface of PtCoFe-CoFeOx@N-HHCS promotes the release of Pt and enhances the electron transfer rate through interfacial interaction, significantly improving the catalyst activity. The confinement effect of the nitrogen-doped ultrathin carbon layer prevents Pt dissolution and enhances the stability of the catalyst. The hierarchical-porous hollow structure provides rapid mass transfer channels for the methanol oxidation reaction, enhancing the reaction rate. The synergistic effect of multiple approaches endows PtCoFe-CoFeOx@N-HHCS with good methanol oxidation performance. This work provides important prospects for preparing highly active, stable, and low-loading Pt catalysts.

Designer topological-single-atom catalysts with site-specific selectivity

Designing catalysts with well-defined, identical sites that achieve site-specific selectivity, and activity remains a significant challenge. In this work, we introduce a design principle of topological-single-atom catalysts (T-SACs) guided by density functional theory (DFT) and Ab initio molecular dynamics (AIMD) calculations, where metal single atoms are arranged in asymmetric configurations that electronic shield topologically misorients d orbitals, minimizing unwanted interactions between reactants and the support surface. Mn1/CeO2 catalysts, synthesized via a charge-transfer-driven approach, demonstrate superior catalytic activity and selectivity for NOx removal. A life-cycle assessment (LCA) reveals that Mn1/CeO2 significantly reduces environmental impact compared to traditional V-W-Ti catalysts. Through in-situ spectroscopic characterizations combined with DFT calculations, we elucidate detailed reaction mechanisms. This study establishes T-SACs as a promising class of catalysts, offering a systematic framework to address catalytic challenges by defining site characteristics. The concept highlights their potential for advancing selective catalytic processes and promoting sustainable technologies.

Active Interfacial Perimeter in Pt/CeO2 Catalysts with Embedding Structure for Water-Tolerant Toluene Combustion

Supported Pt catalysts are often subjected to severe deactivation under the conditions of high temperature and water vapor in catalytic oxidation; thus, the superior stability and water-resistant ability of catalysts have great significance for the effective degradation of volatile organic compounds (VOCs). Herein, we constructed a Pt/CeO2-N catalyst with an active interfacial perimeter, in which Pt species were partially embedded in the defective CeO2-N support to prevent the sintering. A significant charge transfer between Pt species and ceria in the embedding structure occurred via the Pt-CeO2 interface, which induced the formation of a Pt4+-Ov-Ce3+ interfacial structure. Experimental research and theoretical calculations demonstrated that the active Pt4+-Ov-Ce3+ interface promoted the activation and migration of lattice oxygen, thus facilitating the participation of oxygen species in toluene oxidation. Consequently, Pt/CeO2-N showed excellent catalytic performance for toluene degradation. In situ DRIFTS and DFT calculation proved that the Pt4+-Ov-Ce3+ interfacial sites served as the intrinsic active center in the dissociation of H2O to generate ·OH, which contributed to the formation of benzaldehyde, thus remarkably improving the water-resistant property. This study provided a facile strategy for fabricating the interfacial embedding structure to enhance the catalytic activity and water tolerance for eliminating VOCs in practical application.

Metal-Independent Correlations for Site-Specific Binding Energies of Relevant Catalytic Intermediates

Establishing energy correlations among different metals can accelerate the discovery of efficient and cost-effective catalysts for complex reactions. Using a recently introduced coordination-based model, we can predict site-specific metal binding energies (ΔE M) that can be used as a descriptor for chemical reactions. In this study, we have examined a range of metals including Ag, Au, Co, Cu, Ir, Ni, Os, Pd, Pt, Rh, and Ru and found linear correlations between predicted ΔE M and adsorption energies of CH and O (ΔE CH and ΔE O) at various coordination environments for all the considered metals. Interestingly, all the metals correlate with one another under specific surface site coordination, indicating that different metals are interrelated in a particular coordination environment. Furthermore, we have tested and verified for PtPd- and PtIr-based alloys that they follow a similar behavior. Moreover, we have expanded the metal space by taking some early transition metals along with a few s-block metals and shown a cyclic behavior of the adsorbate binding energy (ΔE A) versus ΔE M. Therefore, ΔE CH and ΔE O can be efficiently interpolated between metals, alloys, and intermetallics based on information related to one metal only. This simplifies the process of screening new metal catalyst formulations and their reaction energies.

Effect of H2O and CO2 on CO oxidation over Pt/SSZ-13 with active sites regulated by Lewis acidity

Strategies for controlling the size of metal species using zeolites and their catalytic behavior in industrially relevant processes have attracted widespread attention, but the effect of H2O and CO2 on the catalytic performance of zeolite-based metal catalysts remains obscure. This study investigated the influence of H2O and CO2 on CO oxidation over zeolite-based metal catalysts, along with the precise control of active sites through the regulation of Lewis acidity. It was found that the presence of H2O enhanced CO oxidation and alleviated the inhibitory effect of CO2. Abundant Lewis acid sites of low SiO2/Al2O3 ratios in the Pt/SSZ-13 catalyst facilitate Pt dispersion (61.07%), a high Ptn+/Pt ratio (4.43), and small Pt particles (2.31 nm) formation. In situ DRIFTS revealed that CO2 inhibits CO adsorption and the decomposition of carbon intermediates. Water alters the CO adsorption configuration of Pt0, thereby weakening the Pt-CO bond to promote the CO oxidation reaction. Meanwhile, water dissociated into hydroxyl groups on the surface adsorbs oxygen species, participating in reactions and promoting CO2 production from carbon intermediates. H218O isotope labeling experiments validated the water involvement in the reaction and emphasized the importance of the presence of oxygen species during the water dissociation process. Regulation of Lewis acid sites promotes the Ptn+ species formation, enhancing the CO oxidation activity, while Pt0 species enhance the water-promotion effect.

Ceria-based supported metal catalysts for the low-temperature water-gas shift reaction

Water-gas shift (WGS) reaction is a crucial step for the industrial production of hydrogen or upgrading the hydrogen generated from fossil or biomass sources by removing the residual CO. However, current industrial catalysts for this process, comprising Cu/ZnO and Fe2O3-Cr2O3, suffer from safety or environmental issues. In the past decades, ceria-based materials have attracted wide attention as WGS catalysts due to their abundant oxygen vacancies and tunable metal-support interaction. Strategies through engineering the shape or crystal facet, size of both metal and ceria, interfacial-structure, etc., to alter the performances of ceria-based catalysts have been extensively studied. Additionally, the developments in the in situ techniques and DFT calculations are favorable for deepening the understanding of the reaction mechanism and structure-function relationship at the molecular level, comprising active sites, reaction path/intermediates, and inducements for deactivation. This article critically reviews the literature on ceria-based catalysts toward the WGS reaction, covering the fundamental insight of the reaction path and development in precisely designing catalysts.

Exploring the Impact of Oxygen Vacancies in Co/Pr-CeO2 Catalysts on H2 Production via the Water-Gas Shift Reaction

In this study, we utilized various Pr-doped CeO2 catalysts (Pr=5, 10, 20, and 30 wt.%) as a support medium for the dispersion of cobalt (Co) nanoparticles, aiming to investigate the impact of oxygen vacancies on the water-gas shift (WGS) reaction. Different characterization techniques were employed to understand the insights into the structure-activity relationship governing the performance of Pr doped ceria supported Co catalysts towards WGS reaction. Our findings reveal that Co/Pr-CeO2 catalysts at optimum Pr loading (10 wt.%) exhibit a superior CO conversion (88 %) facilitated by the presence of more oxygen vacancies induced by Pr doping into the CeO2 lattice, as opposed to the performance of the pure Co/CeO2 catalytic system. It was also found that the highest activity was obtained at increased intrinsic oxygen vacancies and strong synergy between Co and Pr/CeO2 support, fostering more favorable CO activation at the interfacial sites, thus accounting for the observed enhanced activity.

Engineering Asymmetric Strain within C-Shaped CeO2 Nanofibers for Stabilizing Sub-3 nm Pt Clusters against Sintering

Ultrafine noble metals have emerged as advanced nanocatalysts in modern society but still suffer from unavoidable sintering at temperatures above 250 °C (e.g., Pt). In this work, closely packed CeO2 grains were confined elegantly in fibrous nanostructures and served as a porous support for stabilizing sub-3 nm Pt clusters. Through precisely manipulating the asymmetry of obtained nanofibers, uneven strain was induced within C-shaped CeO2 nanofibers with tensile strain at the outer side and compressive strain at the inner side. As a result, the enriched oxygen vacancies significantly improved adhesion of Pt to CeO2, thereby boosting the sinter-resistance of ultraclose sub-3 nm Pt clusters. Notably, no aggregation was observed even after exposure to humid air at 750 °C for 12 h, which is far beyond their Tammann temperature (sintering onset temperature, below 250 °C). In situ HAADF-STEM observation revealed a unique sintering mechanism, wherein Pt clusters initially migrate toward the grain boundaries with concentrated stain and undergo slight coalescence, followed by subsequent Ostwald ripening at higher temperatures. Moreover, the sinter-resistant Pt/C-shaped CeO2 effectively catalyzed soot combustion (over 700 °C) in a durable manner. This work provides a new insight for developing sinter-resistant catalysts from the perspective of strain engineering within nano-oxides.

Stabilizing ultra-close Pt clusters on all-in-one CeO2/Al2O3 fibril-in-tubes against sintering

Metal sintering poses significant challenges for developing reliable catalytic systems toward high-temperature reactions, particularly those based on metal clusters with sizes below 3 nm. In this work, electrospun dual-oxide fibril-in-tubes consisting of CeO2 and Al2O3 are rationally designed in an all-in-one manner, to stabilize 2.3 nm Pt clusters with a Tammann temperature (sintering onset temperature) lower than 250 °C. The abundant pores and channels effectively stabilize the Pt clusters physically, while the strong support, CeO2, with high adhesion, pins Pt clusters firmly, and the adjacent weak support, Al2O3, with low adhesion, provides energy barriers to prevent the clusters and emitted Pt atom(s) from moving across the support. Therefore, the ultra-close 2.3 nm Pt clusters, featuring an average nearest neighboring distance of only 2.1 nm, were carefully stabilized against sintering at temperatures exceeding 750 °C, even in oxidative and steam-containing environments. In addition, this catalytic system can efficiently and durably serve in diesel combustion, a high-temperature exothermic reaction, showing no activity decline after 5 cycles. This work provides a comprehensive understanding of sinter-resistant catalytic systems, and presents new insights for the development of advanced nanocatalysts.

Exploring the Facet-Dependent Structural Evolution of Pt/CeO2 Catalysts Induced by Typical Pretreatments for CO Oxidation

Atomic-scale insights into the interactions between metals and supports play a crucial role in optimizing catalyst design, understanding catalytic mechanisms, and enhancing chemical conversion processes. The effects of oxide support on the dynamic behavior of supported metal species during pretreatments or reactions have been attracting a lot of attention; however, very less systematic integrations are carried out experimentally using real catalysts. In this study, we here utilized facet-controlled CeO2 as examples to explore their influence on the supported Pt species (1.0 wt %) during the reducing and oxidizing pretreatments that are typically applied in heterogeneous catalysts. By employing a combination of microscopy, spectroscopy, and first-principles calculations, it is demonstrated that the exposed crystal facets of CeO2 govern the evolution behavior of supported Pt species under different environmental conditions. This leads to distinct local coordinations and charge states of the Pt species, which directly influence the catalytic reactivity and can be leveraged to control the catalytic performance for CO oxidation reactions.

Low Temperature NO and CO Conversion with a Mechanistic Approach on Ru-Composed Cerium Oxide

Catalytic reduction of NO with CO at a lower temperature is an extremely challenging task, thus requiring conceivable surfaces to overcome such issues. Ru-substituted CeO2 catalysts prepared via the solution combustion method were employed in CO oxidation and NO-CO conversion studies. The characterization for material formation and surface structure was carried out through XRD, SEM, TEM, and BET surface area. The catalytic study revealed the promising behavior of 5% Ru in CeO2 for the 100% conversion of NO-CO at 150 °C, proving it to be an excellent exhaust material. These observed results are also supported by temperature-programmed studies, i.e. TPD of NO and CO in addition to NH3-TPD and H2-TPR for their convincible surface interaction that is inclined toward a significant change in the conversion path. Additionally, the proposed mechanism, based on the experimental evidence, sheds light on the NO-CO redox reaction, directing the reaction pathway toward the Langmuir-Hinshelwood and Mars-Van Krevelen-type route. Moreover, the exceptional performance can be attributed to the strategic incorporation of Ru in CeO2, where the strong interaction of Ru-Ce is able to gain a high synergy for NO and CO conversion.

Tuning the Metal-Support Interaction by Modulating CeO2 Oxygen Vacancies to Enhance the Toluene Oxidation Activity of Pt/CeO2 Catalysts

In this research, a range of Pt/CeO2 catalysts featuring varying Pt-O-Ce bond contents were developed by modulating the oxygen vacancies of the CeO2 support for toluene abatement. The Pt/CeO2-HA catalyst generated a maximum quantity of Pt-O-Ce bonds (possessed the strongest metal-support interaction), as evidenced by the visible Raman results, which demonstrated outstanding toluene catalytic performance. Additionally, the UV Raman results revealed that the strong metal-support interaction stimulated a substantial increase in oxygen vacancies, which could facilitate the activation of gaseous oxygen to generate abundant reactive oxygen species accumulated on the Pt/CeO2-HA catalyst surface, a conclusion supported by the H2-TPR, XPS, and toluene-TPSR results. Furthermore, the results from quasi-in situ XPS, in situ DRIFTS, and DFT indicated that the Pt/CeO2-HA catalyst with a strong metal-support interaction led to improved mobility of reactive oxygen species and lower oxygen activation energies, which could transfer a large number of activated reactive oxygen species to the reaction interface to participate in the toluene oxidation, resulting in the relatively superior catalytic performance. The approach of tuning the metal-support interaction of catalysts offers a promising avenue to develop highly active catalysts for toluene degradation.

Schottky Barrier-Based Built-In Electric Field for Enhanced Tumor Photodynamic Therapy

Photodynamic therapy's antitumor efficacy is hindered by the inefficient generation of reactive oxygen species (ROS) due to the photogenerated electron-hole pairs recombination of photosensitizers (PS). Therefore, there is an urgent need to develop efficient PSs with enhanced carrier dynamics. Herein, we designed Schottky junctions composed of cobalt tetroxide and palladium nanocubes (Co3O4@Pd) with a built-in electric field as effective PS. The built-in electric field enhanced photogenerated charge separation and migration, resulting in the generation of abundant electron-hole pairs and allowing effective production of ROS. Thanks to the built-in electric field, the photocurrent intensity and carrier lifetime of Co3O4@Pd were approximately 2 and 3 times those of Co3O4, respectively. Besides, the signal intensity of hydroxyl radical and singlet oxygen increased to 253.4% and 135.9%, respectively. Moreover, the localized surface plasmon resonance effect of Pd also enhanced the photothermal conversion efficiency of Co3O4@Pd to 40.50%. In vitro cellular level and in vivo xenograft model evaluations demonstrated that Co3O4@Pd could generate large amounts of ROS, trigger apoptosis, and inhibit tumor growth under near-infrared laser irradiation. Generally, this study reveals the contribution of the built-in electric field to improving photodynamic performance and provides new ideas for designing efficient inorganic PSs.

New insight into the catalytic mechanism of ester hydrogenation over the Cu/ZnO catalyst: the contribution of hydrogen spillover

The dimethyl maleate hydrogenation activity of Cu, ZnO-X and physically mixed Cu+ZnO-X samples was systematically investigated to probe the essential role of ZnO in ester hydrogenation processes. Cu samples exhibited high CC bond hydrogenation ability with dimethyl succinate as the main product. Comparatively, ZnO was inactive in hydrogenation due to its weak ability to dissociate hydrogen while the CO group could be activated and adsorbed on the ZnO surface. Interestingly, physical mixing with ZnO significantly improved the CO hydrogenation activity of Cu samples. The H2-TPD results reveal the origin of "Cu-ZnO synergy": hydrogen atoms formed on the copper surface can spill over to the ZnO surface and react with the adsorbed CO group.