Metal Support Research Articles

Continuous‐Flow Solution Plasma for the Atom‐Economic Synthesis of Single/Dual‐Atom Catalysts

AbstractSingle‐atom catalysts (SACs) manifest unique advantages in various aspects of catalysis but face challenges in atom‐economic synthesis. Solution reduction holds the promise of fast, continuous, and low‐cost synthesis of SACs, however, almost no chemical, electrochemical, or photochemical reduction can avoid the aggregation of metal atoms in solution. The issue becomes even tougher to composite dual‐atom metals together. Herein, a continuous‐flow solution plasma (CSP) method is developed, which utilizes high‐flux hydrated electrons, hydrogen radicals, and enhanced metal–support interaction, to achieve over 97% capture efficiency of metal precursors to fabricate CeO2‐based single‐atom Au, Rh, Pd, Ru, and Pt in only 0.03‐s residence time. Further, a programmed CSP synthesis of Au1Rh1/CeO2 and Au1Pd1/CeO2 dual‐atom catalysts is demonstrated. Under Xe lamp irradiation, Au1Rh1/CeO2 breaks room temperature constraints in CO conversion for the water–gas shift reaction with a T50 (the temperature at which 50% CO conversion occurs) of 298 K. The innovative CSP technology provides an atom‐economic approach to the continuous production of SACs using clean electricity without any additional reducing agent, paving the way for the programmed and green synthesis of SACs for industrial catalysis, energy conversion, and environment remedy applications.

Catalytic activity of Co/γ-Al2O3 catalysts for decomposition of ammonia to produce hydrogen

This paper aims to study the performance of Co/meso-Al2O3 catalysts for ammonia decomposition to produce hydrogen. High-performance Co/meso-Al2O3 catalysts were prepared using a sequential metal loading approach. The synthesized catalysts were analyzed by several techniques including X-ray diffraction (XRD), N2 physisorption analysis, temperature-programmed reduction (H2-TPR), temperature-programmed desorption (NH3-TPD) and transmission electron microscope (TEM). The effect of metal loading, decomposition temperature and weight hourly space velocity (WHSV) on the catalyst activity were studied. Temperature-programmed desorption (NH3-TPD) analysis showed the coexistence of weak acidic sites and strong acidic sites in the synthesized catalysts, indicative of weak metal–support interaction. The reaction activation energy of the catalysts followed the order of 26Co-CAT(A) < 9Co-CAT(A) < 16Co-CAT(A) < 5Co-CAT(A) < CAT(A). Particularly, 26 Co-CAT(A) exhibited significantly lower activation energy compared to the other catalyst, which was in line with its catalytic activity. This observation indicated that the cobalt loading in 26 Co-CAT(A) resulted in relatively weaker metal-support interactions, leading to lower desorption energy and thus allowing higher NH3 conversion at lower temperatures. These findings offer valuable insights for the development and optimization of advanced Co-based catalysts, facilitating the sustainable and efficient application of ammonia decomposition.

Engineering the Active Sites of MOF‐derived Catalysts: From Oxygen Activation to Activate Metal‐Air Batteries†

Comprehensive SummaryThe electrochemical processes of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play a crucial role in various energy storage and conversion systems. However, the inherently slow kinetics of reversible oxygen reactions present an urgent demand for the development of efficient oxygen electrocatalysts. Recently, metal‐organic framework (MOF) derivatives have attracted extensive attention in electrocatalysis research due to their unique porous structure, abundant active sites, and tunable structural properties. Especially, the optimization of the electronic structure of active sites in MOF derivatives has been proven as an effective strategy to enhance the catalytic activity. In this review, we provide an overview of the electronic structure optimization strategies for active sites in MOF derivatives as advanced catalysts in various O—O bond activation reactions, including the construction of synergistic effects between multiple sites, the development of heterogeneous interfaces, the utilization of metal support interactions, and the precise modulation of organic ligands surrounding catalytic active sites at the atomic level. Furthermore, this review offers theoretical insights into the oxygen activation and catalytic mechanisms of MOF derivatives, as well as the identification of active sites. Finally, the potential challenges and prospects of MOF derivatives in electrocatalysis are discussed. This review contributes to the understanding and advancement of efficient oxygen electrocatalysis in energy systems. Key Scientists

Influence of Oxidation Temperature on the Regeneration of a Commercial Pt-Sn/Al2O3 Propane Dehydrogenation Catalyst

In the propane dehydrogenation process, the structure and catalytic performance stability of the catalyst are determined by its regeneration process, which includes oxidation of coke and oxychlorination to redisperse the supported metal particles. A commercial Pt-Sn catalyst was used in this work to investigate the impact of oxidation temperature on oxychlorination performance. The catalysts after oxidation and oxychlorination were characterized by H2-TPR, CO-DRIFTS, HAADF-STEM, XPS, and CO chemisorption. It was found that mild sintering of Pt occurred during oxidation in the temperature range of 550–650 °C, and the catalyst could be fully restored in the subsequent oxychlorination treatment. Upon oxidation of the catalyst at 700 °C, a severe aggregation of Pt and SnOx could be observed, and the catalyst could not be fully regenerated under the given oxychlorination conditions. However, PDH catalyst deactivation caused by sintering is not irreversible. By tailoring the oxychlorination conditions, the detrimental effect of high oxidation temperature on regeneration could be ruled out. During the oxidation and oxychlorination treatment, the metal tends to migrate to anchor on sites with stronger metal–support interaction, which was helpful for enhancing the catalytic activity.

Surface stress redistribution and thermal performance of tempered vacuum glazing with printing sintering support pillars

The support stress distribution of the printing sintering support pillars (PSSP), which became rounded due to the shrinkage that occurred in sintering formation, was different from that of the conventional cylindrical metal support pillars (CMSP). In this paper, ANSYS software was used to establish the mechanical simulation model of tempered vacuum glazing with PSSP. The influence of PSSP arrangement (spacing D, and three arrangement styles of square, regular triangle, and regular hexagon) on the mechanical properties of tempered vacuum glazing were analyzed, including the maximum stress σ1max on tempered glass (T-glass) surface, the maximum deformation ω1max of T-glass, and the maximum stress σ2max on the PSSP. The simulation results showed that when the PSSP were arranged in a square with D of 50 mm, σ1max, ω1max, and σ2max were 26.39 MPa, 7.82 μm, and 546.72 MPa, respectively, which met the requirements of the evaluation indexes of mechanical properties of tempered vacuum glazing, and had the least number of PSSP. The mechanical properties of tempered vacuum glazing with regular triangle arrangement of PSSP were better than those of square and regular hexagon arrangements, and the σ1max, ω1max and σ2max of which were 16.24 MPa, 7.25 μm and 489.66 MPa respectively, but with a too large number of PSSP. Optimization of the triangle layout angle and side length could reduce PSSP numbers. When the PSSP were arranged in an isosceles triangle with a 65° base angle and 50 mm bottom length, the mechanical properties of tempered vacuum glazing were the best. The triangular arrangement of PSSP had an optimization effect on the surface stress redistribution of tempered vacuum glazing, and the number of stress peaks was twice that of the square arrangement. Meanwhile, tempered vacuum glazing samples were made and the surface stress, thermal conductivity tests were conducted. The results showed that the measured values of peak and valley stress had an error of ±2.8 MPa compared to the simulated values. The simulation results were reliable and the surface stress redistribution of tempered vacuum glazing was present. The measured heat transfer coefficient of tempered vacuum glazing with PSSP was 0.7402 W m−2 K−1, slightly higher than that of tempered vacuum glazing with CMSP. The difference between them was not significant.

CO2 hydrogenation over rhodium cluster catalyst nucleated within a manganese oxide framework

Rhodium-based manganese oxide frameworks were explored as a prototype for carbon dioxide reactive capture and conversion. Three-dimensional frameworks of MnOx were utilized as support structures to isolate Rh metal centers. V, Na, and Zn were introduced as counterions to stabilize the structure and for their beneficial effect as promoters. With this multicomponent catalyst, Rh active centers with MnOxs and varied counterions, we were able to selectively tune the catalytic performance of the material via the choice of counterion and structure of the host material. With cryptomelane-type tunnel manganese oxides octahedral molecular sieve (OMS2), we found that Rh-V-OMS2 was highly stable even after 48 hours on stream with a reaction rate of around 1.5×10−4 mol CO2/gRh/s, surpassing the net reactivity of other initially more active combinations. Furthermore, during CO2 hydrogenation, in situ XAFS showed that single Rh atoms nucleated into nanoparticles/ sub-nanometer clusters with a coordination number of 5.5 or less. Our finding of the correlation between the reaction rate and particle size offers the potential for enhanced control over the reaction rate by tuning particle size. Our activity study with control experiments demonstrates that the activities of the catalysts are proved due to the unique metal support interaction offered by the Rh-X-MnO.

Recent Advances in the Use of Controlled Nanocatalysts in Methane Conversion Reactions

This study investigates the utilization of controlled nanocatalysts in methane conversion reactions, addressing the pressing need for the efficient utilization of methane as a feedstock for valuable chemicals and clean energy. The methods employed include a comprehensive review of recent advancements in nanocatalyst synthesis, characterization, and application, as well as the critical analysis of underlying mechanisms and controversies in methane activation and transformation. The main findings reveal significant progress in the design and synthesis of controlled nanocatalysts, enabling enhanced activity, selectivity, and stability in methane conversion reactions. Moreover, the study highlights the importance of resolving controversies surrounding metal–support interactions for rational catalyst design. Overall, the study underscores the pivotal role of nanotechnology in shaping the future of methane utilization and sustainable energy production, providing valuable insights for guiding future research directions and technological developments in this field.

Ru–CeO2 Nanocatalysts with Weak Metal–Support Interactions for Ethylene Methoxycarbonylation

Ru–CeO₂ Nanocatalysts with Weak Metal–Support Interactions for Ethylene Methoxycarbonylation

Gallium-Promoted Strong Metal–Support Interaction over a Supported Cu/ZnO Catalyst for Methanol Steam Reforming

Gallium-Promoted Strong Metal–Support Interaction over a Supported Cu/ZnO Catalyst for Methanol Steam Reforming

Strategic assembly of active phases on Co-Fe bimetallic catalysts for efficient Fischer-Tropsch synthesis

In the realm of Fischer-Tropsch synthesis (FTS), the escalating cost of cobalt has spurred interest in Co-Fe bimetallic catalysts as substitutes for monometallic Co catalysts. Unfortunately, it is difficult to clarify specific functions and interactions of the two phases, as investigating catalysts in a unified dimension of both metal and support is still a challenge. Herein, we realize precise control over synthesizing nitrogen-doped carbon materials supported bimetallic catalysts containing CoFe alloy and Co + Fe2C dual active phases. The catalysts are comprehensively characterized to address the above problem by excluding the influence of metal sizes and support properties. Our findings reveal that compared to metallic Co alone and Co + Fe2C dual active phases, the Co-Fe interaction in CoFe alloy with electron transfer from Fe to Co optimizes reactant adsorption behaviors through achieving a larger number of strongly adsorbed CO per active site to increase the density of C* adsorbates and a higher surface CO/H2 ratio to inhibit the hydrogenation of CHx* intermediates for chain termination, as well as an appropriate ability for CO adsorption/ dissociation. These advantages collectively enhance both CO activation and C-C coupling, and consequently, the CoFe/NC (CoFe alloy) catalyst exhibits the superior catalytic performance in the cobalt space–time yield in C5+ products (3011.2 gC5+ kgCo−1h−1), which surpasses the Co/NC (monometallic Co) and Co + Fe/NC (Co + Fe2C dual active phases) by 2.2 times and 2.4 times, respectively. This study serves as a promising route for the development of efficient and low-cost bimetallic catalysts through the strategic arrangement of multiple active phases for various reactions.

Exploring the Interfacial Hydrogen Transfer between Pt and the Siliceous Framework and Its Promotional Effect on the Isotope Catalytic Exchange.

Interfacial hydrogen transfer between metal particles and catalyst supports is a ubiquitous phenomenon in heterogeneous catalysis, and this occurrence on reducible supports has been established, yet controversies remain about how hydrogen transfer can take place on nonreducible supports, such as silica. Herein, highly dispersed Pt clusters supported on a series of porous silica materials with zeolitic or/and amorphous frameworks were prepared to interrogate the nature of hydrogen transfer and its promotional effect on H2-HDO isotope catalytic exchange. The formation of zeolitic frameworks upon these porous silica supports by hydrothermal crystallization greatly promotes the interfacial hydrogen bidirectional migration between metal clusters and supports. Benefiting from this transfer effect, the isotope exchange rate is enhanced by 10 times compared to that on the amorphous counterpart (e.g., Pt/SBA-15). In situ spectroscopic and theoretical studies suggest that the defective silanols formed within the zeolite framework serve as the reactive sites to bind HDO or H2O by hydrogen bonds. Under the electrostatic attraction interaction, the D of hydrogen-bonded HDO scrambles to the Pt site and the dissociated H on Pt simultaneously spills back to the electronegative oxygen atom of adsorbed water to attain H-D isotope exchange with an energy barrier of 0.43 eV. The reverse spillover D on Pt combines with the other H on Pt to form HD in the effluent. We anticipate that these findings are able to improve our understanding of hydrogen transfer between metal and silica supports and favor the catalyst design for the hydrogen-involving reaction.

Advances on Single‐Atom‐Based Dual‐Site Photocatalysts: Fundamentals, Mechanisms, and Applications

Single‐atom catalysts (SACs) have emerged as leading‐edge research in the field of photocatalysis due to outstanding photocatalytic performance, maximum atomic utilization efficiency, and well‐defined catalytic active sites. However, the singular functionality of active sites in SACs restricts their applications in complex redox reactions involving multiple intermediates and reaction pathways. To circumvent this limitation, a second site comprising single atoms (SA), alloys, clusters, or nanoparticles is proposed to establish SA‐based dual‐site photocatalysts (SA DSPs). While maintaining 100% atomic utilization, the second site and site–site collaboration endow SA DSPs with superior photocatalytic activities to surpass those of SACs. In this review, the latest investigations on SA DSPs featuring diverse compositions, electronic and geometric configurations, site–site collaboration, and metal–support interactions are summarized. Thereafter, the mechanisms underlying enhanced photocatalytic activities are elucidated regarding the roles of the dual sites in charge‐carrier dynamics and surface reactivity. Furthermore, the state‐of‐the‐art applications in photocatalytic hydrogen evolution, CO2 reduction, and methane oxidation, etc., over SA DSPs are discussed. It is anticipated that this review will offer insights into precise control and design of dual sites in photocatalysts, thereby advancing photocatalysis toward commercial viability.

Facile synthesis of iron nanoparticles from Camellia Sinensis leaves catalysed for biodiesel synthesis from Azolla filiculoides

Recent years have seen an increase in research on biodiesel, an environmentally benign and renewable fuel alternative for traditional fossil fuels. Biodiesel might become more cost-effective and competitive with diesel if a solid heterogeneous catalyst is used in its production. One way to make biodiesel more affordable and competitive with diesel is to employ a solid heterogeneous catalyst in its manufacturing. Based on X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR), the researchers in this study proved their hypothesis that iron oxide core–shell nanoparticles were generated during the green synthesis of iron-based nanoparticles (FeNPs) from Camellia Sinensis leaves. The fabrication of spherical iron nanoparticles was successfully confirmed using scanning electron microscopy (SEM). As a heterogeneous catalyst, the synthesised catalyst has shown potential in facilitating the conversion of algae oil into biodiesel. With the optimal parameters (0.5 weight percent catalytic load, 1:6 oil—methanol ratio, 60 °C reaction temperature, and 1 h and 30 min reaction duration), a 93.33% yield was attained. This may be due to its acid–base property, chemical stability, stronger metal support interaction. Furthermore, the catalyst was employed for transesterification reactions five times after regeneration with n-hexane washing followed by calcination at 650 °C for 3 h.

Origin of the synergistic effects of bimetallic nanoparticles coupled with a metal oxide heterostructure for accelerating catalytic performance

AbstractPrecisely tuning bicomponent intimacy during reactions by traditional methods remains a formidable challenge in the fabrication of highly active and stable catalysts because of the difficulty in constructing well‐defined catalytic systems and the occurrence of agglomeration during assembly. To overcome these limitations, a PtRuPNiO@TiOx catalyst on a Ti plate was prepared by ultrasound‐assisted low‐voltage plasma electrolysis. This method involves the oxidation of pure Ti metal and co‐reduction of strong metals at 3000°C, followed by sonochemical ultrasonication under ambient conditions in an aqueous solution. The intimacy of the bimetals in PtRuPNiO@TiOx is tuned, and the metal nanoparticles are uniformly distributed on the porous titania coating via strong metal‒support interactions by leveraging the instantaneous high‐energy input from the plasma discharge and ultrasonic irradiation. The intimacy of PtRuPNiO@TiOx increases the electron density on the Pt surface. Consequently, the paired sites exhibit a high hydrogen evolution reaction activity (an overpotential of 220 mV at a current density of 10 mA cm−2 and Tafel slope of 186 mV dec−1), excellent activity in the hydrogenation of 4‐nitrophenol with a robust stability for up to 20 cycles, and the ability to contrast stated catalysts without ultrasonication and plasma electrolysis. This study facilitates industrially important reactions through synergistic chemical interactions.

Modulation of metal–support interactions in Pt–TiOx synergistic catalysts for propane dehydrogenation

The strong metal-support interaction exerts a significant influence on the catalytic performance of the metal active site. This paper describes the modulation of the coverage of TiOx on the Pt nanoparticles via the pretreatment atmosphere, and its influence of the catalytic performance for propane dehydrogenation. The direct reduction in H2 at 600 °C of the Pt/TiO2-Al2O3 catalyst induces partial coverage of the Pt nanoparticles by TiOx. This partial coverage with TiOx leads to higher electron density over platinum than catalysts treated through air calcination followed by reduction, which can enhance the selectivity of propylene. Furthermore, the presence of TiOx in the catalysts can promote C–H activation during propane dehydrogenation. Eventually, this synergistic catalyst presents a high formation rate of propylene (141.1 mmol·gcat-1·h−1) and propylene selectivity of ∼ 91 % with a low deactivation rate of 0.09 h−1. This study unveils an effective approach to modulate the catalytic performance of metals supported on oxides based on metal-support interaction.

Cobalt Phosphide-Supported Single-Atom Pt Catalysts for Efficient and Stable Hydrogen Generation from Ammonia Borane Hydrolysis.

Ammonia borane (AB) has emerged as a promising chemical hydrogen storage material. The development of efficient, stable, and cost-effective catalysts for AB hydrolysis is the key to achieving hydrogen energy economy. Here, cobalt phosphide (CoP) is used to anchor single-atom Pt species, acting as robust catalysts for hydrogen generation from AB hydrolysis. Thanks to the high Pt utilization and the synergy between CoP and Pt species, the optimized Pt/CoP-100 catalyst exhibits an unprecedented hydrogen generation rate, giving a record turnover frequency (TOF) value of 39911 and turnover number of 2926829 at room temperature. These metrics surpass those of all existing state-of-the-art supported metal catalysts by an order of magnitude. Density functional theory calculations reveal that the integration of single-atom Pt onto the CoP substrate significantly enhances adsorption and dissociation processes for both water and AB molecules, thereby facilitating hydrogen production from AB hydrolysis. Interestingly, the TOF value is further elevated to 54878 under UV-vis light irradiation, which can be attributed to the efficient separation and mobility of photogenerated carriers at the Pt-CoP interface. The findings underscore the effectiveness of CoP as a support for single-atom metals in hydrogen production, offering insights for designing high-performance catalysts for chemical hydrogen storage.

Cyclo[16]carbon through the lens of density functional theory: Role of impurity decoration in hydrogen evolution reaction

The increasing global demand for sustainable energy sources has intensified the search for cost-effective catalysts in the hydrogen evolution reaction (HER). Single-atom catalysts (SACs) supported on suitable substrates have emerged as promising alternatives. In this study, we investigate the utilization of cyclo[16]carbon (C16 nanocluster) as a support for second-row transition metals (TMs) based SACs. The exploration focuses on analyzing the geometry, electronic properties, stability, and catalytic performance of TM@C16 SACs in the context of HER. Notably, highly negative binding energy values, structural modifications, and altered dipole moments collectively affirm the strong binding between the TMs and the C16 nanocluster. The incorporation of TMs onto the C16 nanocluster substantially enhances the conductivity of the latter. Studied SACs primarily showed H2 evolution via Volmer-Heyrovsky mechanisms. Notably, Pd@C16 and Rh@C16 displayed superior catalytic performance, with ΔGHV values of −0.007 eV and 0.05 eV, respectively. The determination of the exchange current via a volcano plot as a function of Gibbs free energy for hydrogen evolution over these designed SACs further validates their efficacy. Our findings establish Pd@C16 and Rh@C16 as highly stable and efficient SACs for the HER, underscoring their potential in advancing sustainable energy technologies.

Atmosphere-Dependent Strong Metal–Support Interactions in Au/ZnO Catalysts and Their Overlayer Permeability

Atmosphere-Dependent Strong Metal–Support Interactions in Au/ZnO Catalysts and Their Overlayer Permeability

Improvement on electrochemiluminescence properties of graphite carbon nitride by metal oxidation state regulation

AbstractReasonable design is of great significance for improving the performance of electrochemiluminescence (ECL) co‐reactant accelerators. The different d‐band structure of metal single atoms will produce different oxidation states, which may change the adsorption of reaction intermediates to the catalyst and affect its catalytic activity. In this study, we have demonstrated that the ECL performances of graphite carbon nitride (CN) can be promoted by modulating the metal oxidation states of co‐reaction accelerator for the first time. The oxidation states of Au were modulated by the different electronic metal–support interaction (EMSI) between the co‐reaction accelerator (Au single atoms, Au nanoparticles [Au NPs]) and CN, and the effects of Au oxidation states on the ECL performances of CN were investigated. Comparison to pristine CN and CN nanosheets supported Au nanoparticles (Au NPs/CN), stronger and more stable ECL intensity of CN nanosheets supported Au single‐atoms (AuS/CN) was obtained. The ECL signal of AuS/CN was about 32.2 times that of the original CN, and 2.8 times that of Au NPs/CN in the same Au loading content (0.8%). Detailed mechanism revealed that AuS/CN with higher Au oxidation state has better conductivity and stronger catalytic activity, which promotes the electric reduction of CN and S2O82−, increases the lifetime of the excited state CN*, and significantly improves the ECL performance of CN. In addition, this work provides a detailed understanding of the essence of EMSI for the ECL intensity amplification and established a feasible method for the improvement of ECL capacities of co‐reactant accelerators.

Cooperation between single atom catalyst and support to promote nitrogen electroreduction to ammonia: A theoretical insight

The co-catalysis between single atom catalyst (SAC) and its support has recently emerged as a promising strategy to synergistically boost the catalytic activity of some complex electrochemical reactions, encompassing multiple intermediates and pathways. Herein, we utilized defective BC3 monolayer-supported SACs as a prototype to investigate the cooperative effects of SACs and their support on the catalytic performance of the nitrogen reduction reaction (NRR) for ammonia (NH3) production. The results showed that these SACs can be firmly stabilized on these defective BC3 supports with high stability against aggregation. Furthermore, co-activation of the inert N2 reactant was observed in certain embedded SACs and their neighboring B atoms on certain BC3 sheets due to the noticeable charge transfer and significant N–N bond elongation. Our high-throughput screening revealed that the Mo/DVCC and W/DVCC exhibit superior NRR catalytic performance, characterized by a low limiting potential of −0.33 and −0.43 V, respectively, which can be further increased under acid conditions based on the constant potential method. Moreover, varying NRR catalytic activities can be attributed to the differences in the valence state of active sites. Remarkably, further microkinetic modeling analysis displayed that the turnover frequency of N2–to–NH3 conversion on Mo/DVCC is as large as 1.20 × 10−3 s−1 site−1 at 700 K and 100 bar, thus guaranteeing its ultra-fast reaction rate. Our results not only suggest promising advanced electrocatalysts for NRR but also offer an effective avenue to regulate the electrocatalytic performance via the co-catalytic metal–support interactions.