Nickel@Siloxene catalytic nanosheets for high-performance CO2 methanation

Highly Stable and Selective Ni/ZrO2 Nanofiber Catalysts for Efficient CO2 Methanation

Ni-based oxides are promising catalysts for CO2 methanation. However, Ni-based catalysts also have some unresolved issues and drawbacks in practical applications. The activity and selectivity of Ni-based catalysts in CO2 methanation at low temperatures still need to be improved. Here, Ni/ZrO2 nanofibers with high surface areas (up to 101.2 m2/g) were prepared by electrospinning methods. The Ni/ZrO2-ES (also named as 66Ni/ZrO2) catalyst showed excellent catalytic performance in CO2 methanation (the CO2 conversion = 81% and CH4 selectivity = 99% at 350 °C) and excellent stability for 100 h, which was better than most reported Ni/ZrO2 catalysts. However, the comparison sample Ni/ZrO2-CP prepared by the coprecipitation method had poor catalytic performance (the CO2 conversion = 54% and CH4 selectivity = 90% at 350 °C). Within 100 h, the CO2 conversion decreased to 30% and the CH4 selectivity decreased to 52%. Both EPR and O1S XPS confirmed that Ni/ZrO2 nanofibers can form more reactive oxygen species vacancies, and CO2-TPD confirmed that nanofibers had more CO2 adsorption sites compared with the control sample Ni/ZrO2-CP. In situ DRIFTS analysis showed that bidentate carbonate and monodentate carbonate were key intermediates in CO2 methanation. The catalytic performance of Ni/ZrO2 nanofiber catalysts would be attributed to higher dispersion of Ni species on the surface of nanofibers, high specific surface area (101.2 m2/g), more oxygen vacancies, more CO2 adsorption sites, and the synergistic effect between Ni nanoparticles and ZrO2 nanofibers. This work may inspire the rational design of Ni/ZrO2 nanofiber catalysts with rich oxygen vacancies for low-temperature CO2 methanation.

Cu-Pd bimetal-decorated siloxene nanosheets for semi-hydrogenation of acetylene

Metallic Pd has been proved highly promising when paired with Cu for industrially important acetylene semi-hydrogenation. Herein, we demonstrate that high-surface-area siloxene can feasibly enable alloying between Pd and Cu via room-temperature reduction with Si-H bonds. Unprecedentedly small Cu nanoparticles with isolated Pd were in situ loaded on siloxene, addressing the core problem of low selectivity of Pd and low activity of Cu. This devised structure outclassed the traditional impregnated SiO2 in every aspect of the catalytic performance for the semi-hydrogenation of acetylene under industry conditions, with a 91% acetylene conversion and an impressive 93% selectivity to ethylene at 200 °C, and showed long-term stability with negligible activity decay at this harsh temperature. This work provides new insights for the design of economic bimetallic loaded catalysts for balancing the activity-selectivity dilemma, demonstrating the viability of siloxene as both a synthetic reagent and a carrier material for efficient catalysis.

Enabling Uniform and Stable Lithium-Ion Diffusion at the Ultrathin Artificial Solid-Electrolyte Interface in Siloxene Anodes

Constructing a stable and robust solid electrolyte interphase (SEI) has a decisive influence on the charge/discharge kinetics of lithium-ion batteries (LIBs), especially for silicon-based anodes which generate repeated destruction and regeneration of unstable SEI films. Herein, a facile way is proposed to fabricate an artificial SEI layer composed of lithiophilic chitosan on the surface of two-dimensional siloxene, which has aroused wide attention as an advanced anode for LIBs due to its special characteristics. The optimized chitosan-modified siloxene anode exhibits an excellent reversible cyclic stability of about 672.6 mAh g-1 at a current density of 1000 mA g-1 after 200 cycles and 139.9 mAh g-1 at 6000 mA g-1 for 1200 cycles. Further investigation shows that a stable and LiF-rich SEI film is formed and can effectively adhere to the surface during cycling, redistribute lithium-ion flux, and enable a relatively homogenous lithium-ion diffusion. This work provides constructive guidance for interface engineering strategy of nano-structured silicon anodes.

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.

Thermally stable Ni foam-supported inverse CeAlOx/Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO2 hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO2 methanation reaction due to the irreversible sintering and coke deposition caused by the inevitable localized hotspots generated during the vigorously exothermic reaction. Herein, we demonstrate the inverse CeAlOx/Ni composite constructed on the Ni-foam structure support realizes remarkable CO2 methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C. Significantly, CeAlOx/Ni/Ni-foam catalyst maintains its initial activity after seven drastic heating-cooling cycles from RT to 240 to 600 °C. Meanwhile, the structure catalyst also shows water resistance and long-term stability under reaction condition. The promising thermal stability and water-resistance of CeAlOx/Ni/Ni-foam originate from the excellent heat and mass transport efficiency which eliminates local hotspots and the formation of Ni-foam stabilized CeAlOx/Ni inverse composites which effectively anchored the active species and prevents carbon deposition from CH4 decomposition.

Easily deposited ZnO nanorods on siloxene nanosheets: investigation of morphological, dielectric, ferroelectric, and energy storage properties

The integration of metal oxides onto two-dimensional layered siloxene has proven to be an effective strategy for expanding potential applications across diverse fields. Herein, we present the synthesis and detailed characterization of zinc oxide (ZnO) nanorods deposited on siloxene nanosheets using the wet chemical precipitation method without the need of alkali. The presence of ZnO nanorods was confirmed through electron microscopy analyses. X-ray diffraction analysis further verified the presence of characteristic peaks of ZnO in the hexagonal wurtzite crystal structure. Dielectric measurements demonstrated the moderated stability of interfacial polarization in siloxene nanosheets doped with zinc oxide (SX-ZnO) over a broad frequency spectrum, coupled with minimal electrical loss values under 0.4 within the 100 Hz to 1 MHz frequency range. In addition, the ferroelectric study of SiNSs-ZnO composites revealed a slim hysteresis loop with maximum polarization and remnant polarization values that varied with reaction times. The SX-ZnO sample prepared for 5 h exhibited the best stored energy properties, featuring a moderate stored energy density (Ws = 771.94 mJ cm-3) and a high energy efficiency of 83.38%. This investigation underscores that the modification of siloxene layers through the deposition of nanostructured transition metal oxide materials leads to stabilized interfacial polarization and enhanced efficient energy storage.

Photothermal Synergistic Catalysis over Defective Zn3In2S6 for CO2 Fixation

Carbon dioxide (CO2) cycloaddition not only produces highly valued cyclic carbonate but also utilizes CO2 as C1 resources with 100% atomic efficiency. However, traditional catalytic routes still suffer from inferior catalytic efficiency and harsh reaction conditions. Developing multienergy-field catalytic technology with expected efficiency offers great opportunity for satisfied yield under mild conditions. Herein, Zn3In2S6 with sulfur vacancies (Sv) was fabricated with the assistance of cetyltrimethylammonium bromide (CTAB), which is further employed for photothermally driven CO2 cycloaddition first. Photoluminescence spectroscopy and photoelectrochemical characterization demonstrated its superior separation kinetics of photoinduced carriers induced by defect engineering. The temperature-programmed desorption (TPD) technique indicated its excellent Lewis acidity-basicity characters. Due to the combination of above merits from photocatalysis and thermal catalysis, defective Zn3In2S6-Sv achieved a yield as high as 73.2% for cyclic carbonate at 80 °C under blue LED illumination within 2 h (apparent quantum yield of 0.468% under illumination of 380 nm monochromatic light at 36 mW·cm-2), which is 2.9, 2.0, and 6.9 times higher than that in dark conditions and those of pristine Zn3In2S6 and industrial representative tetrabutylammonium bromide (TBAB) thermal-catalysis process under the same conditions, respectively. The synergistic reaction path of photocatalysis and thermal catalysis was discriminated by theoretical calculation. This work provides new insights into the photothermal synergistic catalysis CO2 cycloaddition with defective ternary metal sulfides.

Chemically exfoliated boron nanosheets for efficient oxidative dehydrogenation of propane

Oxidative dehydrogenation of propane (ODHP) is a promising technique for producing propene due to its low operative temperature and coke-resistant feature. Recently, boron-based catalysts have been widely investigated for ODHP owing to their brilliant performance. Herein, we report that boron in the form of nanosheets can be prepared feasibly by exfoliating layered MgB2 with hydrochloric acid, and can efficiently and stably catalyze ODHP. At 530 °C, the catalyst exhibits propene and ethene selectivities as high as 63.5% and 18.4%, respectively, at a 40% propane conversion. The olefin productivity reaches 2.48 golefin gcat-1 h-1, superior to the commercial h-BN and other reported boron-based catalysts. Even after testing for 100 h at 530 °C, the catalyst still maintains excellent stability. This work expands the effective boron-based catalyst family for ODHP and demonstrates the great potential of the new type of 2D material-boron nanosheet for energy and catalytic applications.

Boosting Low-Temperature CO2 Hydrogenation over Ni-based Catalysts by Tuning Strong Metal-Support Interactions

Rational design of low-cost and efficient transition-metal catalysts for low-temperature CO2 activation is significant and poses great challenges. Herein, a strategy via regulating the local electron density of active sites is developed to boost CO2 methanation that normally requires >350 °C for commercial Ni catalysts. An optimal Ni/ZrO2 catalyst affords an excellent low-temperature performance hitherto, with a CO2 conversion of 84.0 %, CH4 selectivity of 98.6 % even at 230 °C and GHSV of 12,000 mL g-1  h-1 for 106 h, reflecting one of the best CO2 methanation performance to date on Ni-based catalysts. Combined a series of in situ spectroscopic characterization studies reveal that re-constructing monoclinic-ZrO2 supported Ni species with abundant oxygen vacancies can facilitate CO2 activation, owing to the enhanced local electron density of Ni induced by the strong metal-support interactions. These findings might be of great aid for construction of robust catalysts with an enhanced performance for CO2 emission abatement and beyond.

Research Progress of Non-Noble Metal Catalysts for Carbon Dioxide Methanation

The extensive utilization of fossil fuels has led to a rapid increase in atmospheric CO2 concentration, resulting in various environmental issues. To reduce reliance on fossil fuels and mitigate CO2 emissions, it is important to explore alternative methods of utilizing CO2 and H2 as raw materials to obtain high-value-added chemicals or fuels. One such method is CO2 methanation, which converts CO2 and H2 into methane (CH4), a valuable fuel and raw material for other chemicals. However, CO2 methanation faces challenges in terms of kinetics and thermodynamics. The reaction rate, CO2 conversion, and CH4 yield need to be improved to make the process more efficient. To overcome these challenges, the development of suitable catalysts is essential. Non-noble metal catalysts have gained significant attention due to their high catalytic activity and relatively low cost. In this paper, the thermodynamics and kinetics of the CO2 methanation reaction are discussed. The focus is primarily on reviewing Ni-based, Co-based, and other commonly used catalysts such as Fe-based. The effects of catalyst supports, preparation methods, and promoters on the catalytic performance of the methanation reaction are highlighted. Additionally, the paper summarizes the impact of reaction conditions such as temperature, pressure, space velocity, and H2/CO2 ratio on the catalyst performance. The mechanism of CO2 methanation is also summarized to provide a comprehensive understanding of the process. The objective of this paper is to deepen the understanding of non-noble metal catalysts in CO2 methanation reactions and provide insights for improving catalyst performance. By addressing the limitations of CO2 methanation and exploring the factors influencing catalyst effectiveness, researchers can develop more efficient and cost-effective catalysts for this reaction.

Niobium Modification of CeO2 Tuning Electron Density of Nickel-Ceria Interfacial Sites for Enhanced CO2 Methanation

CO2 methanation has attracted considerable attention as a promising strategy for recycling CO2 and generating valuable methane. This study presents a niobium-doped CeO2-supported Ni catalyst (Ni/NbCe), which demonstrates remarkable performance in terms of CO2 conversion and CH4 selectivity, even when operating at a low temperature of 250 °C. Structural analysis reveals the incorporation of Nb species into the CeO2 lattice, resulting in the formation of a Nb-Ce-O solid solution. Compared with the Ni/CeO2 catalyst, this solid solution demonstrates an improved spatial distribution. To comprehend the impact of the Nb-Ce-O solid solution on refining the electronic properties of the Ni-Ce interfacial sites, facilitating H2 activation, and accelerating the hydrogenation of CO2* into HCOO*, in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis and density functional theory (DFT) calculations were conducted. These investigations shed light on the mechanism through which the activity of CO2 methanation is enhanced, which differs from the commonly observed CO* pathway triggered by oxygen vacancies (OV). Consequently, this study provides a comprehensive understanding of the intricate interplay between the electronic properties of the catalyst's active sites and the reaction pathway in CO2 methanation over Ni-based catalysts.

Ir-CoO Active Centers Supported on Porous Al2 O3 Nanosheets as Efficient and Durable Photo-Thermal Catalysts for CO2 Conversion

Photo-thermal catalytic CO₂ hydrogenation is currently extensively studied as one of the most promising approaches for the conversion of CO₂ into value-added chemicals under mild conditions; however, achieving desirable conversion efficiency and target product selectivity remains challenging. Herein, the fabrication of Ir-CoO/Al₂ O₃ catalysts derived from Ir/CoAl LDH composites is reported for photo-thermal CO₂ methanation, which consist of Ir-CoO ensembles as active centers that are evenly anchored on amorphous Al₂ O₃ nanosheets. A CH₄ production rate of 128.9 mmol g_cat⁻ ¹ h⁻¹  is achieved at 250 °C under ambient pressure and visible light irradiation, outperforming most reported metal-based catalysts. Mechanism studies based on density functional theory (DFT) calculations and numerical simulations reveal that the CoO nanoparticles function as photocatalysts to donate electrons for Ir nanoparticles and meanwhile act as "nanoheaters" to effectively elevate the local temperature around Ir active sites, thus promoting the adsorption, activation, and conversion of reactant molecules. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) demonstrates that illumination also efficiently boosts the conversion of formate intermediates. The mechanism of dual functions of photothermal semiconductors as photocatalysts for electron donation and as nano-heaters for local temperature enhancement provides new insight in the exploration for efficient photo-thermal catalysts.

Surface Ru-H Bipyridine Complexes-Grafted TiO2 Nanohybrids for Efficient Photocatalytic CO2 Methanation

A series of novel surface Ru-H bipyridine complexes-grafted TiO₂ nanohybrids were for the first time prepared by a combined procedure of surface organometallic chemistry with post-synthetic ligand exchange for photocatalytic conversion of CO₂ to CH₄ with H₂ as electron and proton donors under visible light irradiation. The selectivity toward CH₄ increased to 93.4% by the ligand exchange of 4,4'-dimethyl-2,2'-bipyridine (4,4'-bpy) with the surface cyclopentadienyl (Cp)-RuH complex and the CO₂ methanation activity was enhanced by 4.4-fold. An impressive rate of 241.2 μL·g^-1·h^-1 for CH₄ production was achieved over the optimal photocatalyst. The femtosecond transient IR absorption results demonstrated that the hot electrons were fast injected in 0.9 ps from the photoexcited surface 4,4'-bpy-RuH complex into the conduction band of TiO₂ nanoparticles to form a charge-separated state with an average lifetime of ca. 50.0 ns responsible for the CO₂ methanation. The spectral characterizations indicated clearly that the formation of CO₂^•- radicals by single electron reduction of CO₂ molecules adsorbed on surface oxygen vacancies of TiO₂ nanoparticles was the most critical step for the methanation. Such radical intermediates were inserted into the explored Ru-H bond to generate Ru-OOCH species and finally CH₄ and H₂O in the presence of H₂.

Enhanced Optical and Electronic Properties of Silicon Nanosheets by Phosphorus Doping Passivation

In this paper, we use the spin-on-dopant technique for phosphorus doping to improve the photoelectric properties of soft-chemical-prepared silicon nanosheets. It was found that the luminescence intensity and luminescence lifetime of the doped samples was approximately 4 fold that of the undoped samples, due to passivation of the surface defects by phosphorus doping. Meanwhile, phosphorus doping combined with high-temperature heat treatment can reduce the resistivity of multilayer silicon nanosheets by 6 fold compared with that of as-prepared samples. In conclusion, our work brings soft-chemical-prepared silicon nanosheets one step closer to practical application in the field of optoelectronics.

High surface area siloxene for photothermal and electrochemical catalysis

Catalysis based on two-dimensional silicon has been under intense investigation recently. However, its substandard catalytic activity is far from industrialization. In this work, we demonstrate a new solution to this problem formulated on the batch synthesis of siloxene with an enhanced specific surface area (217.8 m² g^-1). A two-dimensional porous structure was prepared, enabling great support and dispersion of metal nanoparticles. Catalytic evaluations of such hybrid structures for the (photo)thermal CO₂ hydrogenation reaction and the electrochemical hydrogen evolution reaction revealed a significant performance advantage over the benchmark two-dimensional silicon structures synthesized via the conventional method. This work may confer notable viability on two-dimensional silicon for advanced energy, catalytic, and environmental applications.

Accommodation of Two-Dimensional SiOx in a Point-to-Plane Conductive Network Composed of Graphene and Nitrogen-Doped Carbon for Robust Lithium Storage

Silicon oxides (SiO_x) are one of the most promising anode materials for next-generation lithium-ion batteries owing to their abundant reserve and low lost and high reversible capacity. However, the practical application of SiO_x is still hindered by their intrinsically low conductivity and huge volume change. In this regard, we design a novel anode material in which sheet-like SiO_x nanosheets are encapsulated in a unique point-to-plane conductive network composed of graphene flakes and nitrogen-doped carbon spheres. This unique composite structure demonstrates high specific capacity (867.7 mAh g^-1 at 0.1 A g^-1), superior rate performance, and stable cycle life. The electrode delivers a superior reversible discharge capacity of 595.8 mAh g^-1 after 200 cycles at 1.0 A g^-1 and 287.5 mAh g^-1 after 500 cycles at 5.0 A g^-1. This work may shed light on the rational design of SiO_x-based anode materials for next-generation high-performance lithium-ion batteries.

Highly Active Ni-Ru Bimetallic Catalyst Integrated with MFI Zeolite-Loaded Cerium Zirconium Oxide for Dry Reforming of Methane

The dry reforming of methane (DRM) is a new potential technology that converts two major greenhouse gases into useful chemical feedstocks. The main challenge faced by this process is maintaining the catalyst with high catalytic activity and long-term stability. Here, a simple and effective preparation route for the synthesis of functional nanomolecular sieve catalysts (NiRu_xCZZ5) from kaolinite tailings was developed for dry reforming of methane with CO₂. The silica monoliths with flower-like spherical and micropore structures (ZSM-5) were prepared by crystal growth method, and the metal components were loaded by ultrasonic-assisted impregnation method. The NiRu_0.5CZZ5 catalyst exhibited excellent catalytic performance (maxmium CO₂ and CH₄ conversions up to 100 and 95.6%, respectively) and very good stability (up to 100h). The interfacial confinement and the strong support interaction are principally responsible for the excellent catalytic activity of the catalyst. The in situ DRIFTS was used to elucidate the possible carbon conversion steps, and stable surface intermediates were also identified.

Grave-to-cradle upcycling of Ni from electroplating wastewater to photothermal CO2 catalysis

Treating hazardous waste Ni from the electroplating industry is mandated world-wide, is exceptionally expensive, and carries a very high CO₂ footprint. Rather than regarding Ni as a disposable waste, the chemicals and petrochemicals industries could instead consider it a huge resource. In the work described herein, we present a strategy for upcycling waste Ni from electroplating wastewater into a photothermal catalyst for converting CO₂ to CO. Specifically, magnetic nanoparticles encapsulated in amine functionalized porous SiO₂, is demonstrated to efficiently scavenge Ni from electroplating wastewater for utilization in photothermal CO₂ catalysis. The core-shell catalyst architecture produces CO at a rate of 1.9 mol·g_Ni^-1·h^-1 (44.1 mmol·g_cat^-1·h^-1), a selectivity close to 100%, and notable long-term stability. This strategy of upcycling metal waste into functional, catalytic materials offers a multi-pronged approach for clean and renewable energy technologies.

Silica-Decorated NiAl-Layered Double Oxide for Enhanced CO/CO2 Methanation Performance

CO/CO₂ hydrogenation has attracted much attention as a pathway to achieve carbon neutrality and production of synthetic natural gas (SNG). In this work, two-dimensional NiAl layered double oxide (2D NiAl-LDO) has been successfully decorated by SiO₂ nanoparticles derived from SiCl₄ and used as CO/CO₂ methanation catalysts. The as-obtained H-SiO₂-NiAl-LDO exhibited a large specific surface area of 201 m²/g as well as high ratio of metallic Ni⁰ species and surface adsorption oxygen that were beneficial for low-temperature methanation of CO/CO₂. The conversion of CO methanation was 99% at 400 °C, and that of CO₂ was 90% at 350 °C. At 250 °C, the CO methanation reached 85% whereas that of CO₂ reached 23% at 200 °C. We believe that this provides a simple method to improve the methanation performance of CO and CO₂ and a strategy for the modification of other similar catalysts.

Research Progress and Reaction Mechanism of CO2 Methanation over Ni-Based Catalysts at Low Temperature: A Review

The combustion of fossil fuels has led to a large amount of carbon dioxide emissions and increased greenhouse effect. Methanation of carbon dioxide can not only mitigate the greenhouse effect, but also utilize the hydrogen generated by renewable electricity such as wind, solar, tidal energy, and others, which could ameliorate the energy crisis to some extent. Highly efficient catalysts and processes are important to make CO2 methanation practical. Although noble metal catalysts exhibit higher catalytic activity and CH4 selectivity at low temperature, their large-scale industrial applications are limited by the high costs. Ni-based catalysts have attracted extensive attention due to their high activity, low cost, and abundance. At the same time, it is of great importance to study the mechanism of CO2 methanation on Ni-based catalysts in designing high-activity and stability catalysts. Herein, the present review focused on the recent progress of CO2 methanation and the key parameters of catalysts including the essential nature of nickel active sites, supports, promoters, and preparation methods, and elucidated the reaction mechanism on Ni-based catalysts. The design and preparation of catalysts with high activity and stability at low temperature as well as the investigation of the reaction mechanism are important areas that deserve further study.

Continuous-Flow Sunlight-Powered CO2 Methanation Catalyzed by γ-Al2O3-Supported Plasmonic Ru Nanorods

Plasmonic CO2 methanation using γ-Al2O3-supported Ru nanorods was carried out under continuous-flow conditions without conventional heating, using mildly concentrated sunlight as the sole and sustainable energy source (AM 1.5, irradiance 5.5–14.4 kW·m−2 = 5.5–14.4 suns). Under 12.5 suns, a CO2 conversion exceeding 97% was achieved with complete selectivity towards CH4 and a stable production rate (261.9 mmol·gRu−1·h−1) for at least 12 h. The CH4 production rate showed an exponential increase with increasing light intensity, suggesting that the process was mainly promoted by photothermal heating. This was confirmed by the apparent activation energy of 64.3 kJ·mol−1, which is very similar to the activation energy obtained for reference experiments in dark (67.3 kJ·mol−1). The flow rate influence was studied under 14.4 suns, achieving a CH4 production plateau of 264 µmol min−1 (792 mmol·gRu−1·h−1) with a constant catalyst bed temperature of approximately 204 °C.

Selective hydrogenation of CO2 to CH4 over two-dimensional nickel silicate molecular sieves

Two-dimensional (2D) Ni-containing delaminated MWW layers (Ni-DML) were synthesized by hydrothermal treatment of a borosilicate MWW precursor with a nickel nitrate solution, and their catalytic properties were investigated for the...

Construction of New Active Sites: Cu Substitution Enabled Surface Frustrated Lewis Pairs over Calcium Hydroxyapatite for CO2 Hydrogenation

Calcium hydroxyphosphate, Ca₁₀ (PO₄ )₆ (OH)₂ , is commonly known as hydroxyapatite (HAP). The acidic calcium and basic phosphate/hydroxide sites in HAP can be modified via isomorphous substitution of calcium and/or hydroxide ions to enable a cornucopia of catalyzed reactions. Herein, isomorphic substitution of Ca²⁺ ions by Cu²⁺ ions especially at very low levels of exchange created new analogs of molecular surface frustrated Lewis pairs (SFLPs) in Cu_x Ca_10-x (PO₄ )₆ (OH)₂ , thereby boosting its performance metrics in heterogeneous CO₂ photocatalytic hydrogenation. In situ Fourier transform infrared spectroscopy characterization and density functional theory calculations provided fundamental insights into the catalytically active SFLPs defined as proximal Lewis acidic Cu²⁺ and Lewis basic OH^- . The photocatalytic pathway proceeds through a formate reaction intermediate, which is generated by the reaction of CO₂ with heterolytically dissociated H₂ on the SFLPs. Given the wealth of information thus uncovered, it is highly likely that this work will spur the further development of similar classes of materials, leading to the advancement and, ultimately, large-scale application of photocatalytic CO₂ reduction technologies.

Highlights and challenges in the selective reduction of carbon dioxide to methanol

Carbon dioxide (CO₂) is the iconic greenhouse gas and the major factor driving present global climate change, incentivizing its capture and recycling into valuable products and fuels. The 6H⁺/6e^- reduction of CO₂ affords CH₃OH, a key compound that is a fuel and a platform molecule. In this Review, we compare different routes for CO₂ reduction to CH₃OH, namely, heterogeneous and homogeneous catalytic hydrogenation, as well as enzymatic catalysis, photocatalysis and electrocatalysis. We describe the leading catalysts and the conditions under which they operate, and then consider their advantages and drawbacks in terms of selectivity, productivity, stability, operating conditions, cost and technical readiness. At present, heterogeneous hydrogenation catalysis and electrocatalysis have the greatest promise for large-scale CO₂ reduction to CH₃OH. The availability and price of sustainable electricity appear to be essential prerequisites for efficient CH₃OH synthesis.

Low temperature methanation of CO2 over an amorphous cobalt-based catalyst

CO2 methanation is an important reaction in CO2 valorization. Because of the high kinetic barriers, the reaction usually needs to proceed at higher temperature (>300 °C). High-efficiency CO2 methanation at low temperature (<200 °C) is an interesting topic, and only several noble metal catalysts were reported to achieve this goal. Currently, design of cheap metal catalysts that can effectively accelerate this reaction at low temperature is still a challenge. In this work, we found that the amorphous Co-Zr0.1-B-O catalyst could catalyze the reaction at above 140 °C. The activity of the catalyst at 180 °C reached 10.7 mmolCO2 gcat -1 h-1, which is comparable to or even higher than that of some noble metal catalysts under similar conditions. The Zr promoter in this work had the highest promoting factor to date among the catalysts for CO2 methanation. As far as we know, this is the first report of an amorphous transition metal catalyst that could effectively accelerate CO2 methanation. The outstanding performance of the catalyst could be ascribed to two aspects. The amorphous nature of the catalyst offered abundant surface defects and intrinsic active sites. On the other hand, the Zr promoter could enlarge the surface area of the catalyst, enrich the Co atoms on the catalyst surface, and tune the valence state of the atoms at the catalyst surface. The reaction mechanism was proposed based on the control experiments.

The Effect of Si on CO2 Methanation over Ni-xSi/ZrO2 Catalysts at Low Temperature

A series of Ni-xSi/ZrO2 (x = 0, 0.1, 0.5, 1 wt%, the controlled contents of Si) catalysts with a controlled nickel content of 10 wt% were prepared by the co-impregnation method with ZrO2 as support and Si as a promoter. The effect of different amounts of Si on the catalytic performance was investigated for CO2 methanation with the stoichiometric H2/CO2 molar ratio (4/1). The catalysts were characterized by BET, XRF, H2-TPR, H2-TPD, H2-chemisorption, CO2-TPD, XRD, TEM, XPS, and TG-DSC. It was found that adding the appropriate amount of Si could improve the catalytic performance of Ni/ZrO2 catalyst at a low reaction temperature (250 °C). Among all the catalysts studied, the Ni-0.1Si/ZrO2 catalyst showed the highest catalytic activity, with H2 and CO2 conversion of 73.4% and 72.5%, respectively and the yield of CH4 was 72.2%. Meanwhile, the catalyst showed high stability and no deactivation within a 10 h test. Adding the appropriate amount of Si could enhance the interaction between Ni and ZrO2, and increase the Ni dispersion, the amounts of active sites including surface Ni0, oxygen vacancies, and strong basic sites on the catalyst surface. These might be the reasons for the high activity and selectivity of the Ni-0.1Si/ZrO2 catalyst.

High-performance light-driven heterogeneous CO2 catalysis with near-unity selectivity on metal phosphides

Akin to single-site homogeneous catalysis, a long sought-after goal is to achieve reaction site precision in heterogeneous catalysis for chemical control over patterns of activity, selectivity and stability. Herein, we report on metal phosphides as a class of material capable of realizing these attributes and unlock their potential in solar-driven CO₂ hydrogenation. Selected as an archetype, Ni₁₂P₅ affords a structure based upon highly dispersed nickel nanoclusters integrated into a phosphorus lattice that harvest light intensely across the entire solar spectral range. Motivated by its panchromatic absorption and unique linearly bonded nickel-carbonyl-dominated reaction route, Ni₁₂P₅ is found to be a photothermal catalyst for the reverse water gas shift reaction, offering a CO production rate of 960 ± 12 mmol g_cat⁻¹ h⁻¹, near 100% selectivity and long-term stability. Successful extension of this idea to Co₂P analogs implies that metal phosphide materials are poised as a universal platform for high-rate and highly selective photothermal CO₂ catalysis.

There exists an urgent need to develop new materials to convert CO₂ to useful products. Here, authors demonstrate metal phosphide nanoparticles to enable light-driven CO₂ hydrogenation with high activities and near-unity selectivity.

Flash Solid-Solid Synthesis of Silicon Oxide Nanorods

1D silicon-based nanomaterials, renowned for their unique chemical and physical properties, have enabled the development of numerous advanced materials and biomedical technologies. Their production often necessitates complex and expensive equipment, requires hazardous precursors and demanding experimental conditions, and involves lengthy processes. Herein, a flash solid-solid (FSS) process is presented for the synthesis of silicon oxide nanorods completed within seconds. The innovative features of this FSS process include its simplicity, speed, and exclusive use of solid precursors, comprising hydrogen-terminated silicon nanosheets and a metal nitrate catalyst. Advanced electron microscopy and X-ray spectroscopy analyses favor a solid-liquid-solid reaction pathway for the growth of the silicon oxide nanorods with vapor-liquid-solid characteristics.

Spontaneous deposition of Ir nanoparticles on 2D siloxene as a high-performance HER electrocatalyst with ultra-low Ir loading

Based on the reducibility of siloxene, Ir nanoparticles were spontaneously deposited on siloxene and showed excellent performance for the HER.

The next big thing for silicon nanostructures – CO2 photocatalysis

Silicon nanostructures for the catalytic conversion of CO₂ to value-added products.

Efficient conversion of CO2 to methane using thin-layer SiOx matrix anchored nickel catalysts

Thin-layer SiO_x matrix anchored nickel catalysts with high specific surface area and a unique electronic/geometric structure were fabricated for efficient CO₂ methanation.