Thermally Stable and Regenerable Platinum-Tin Clusters for Propane Dehydrogenation Prepared by Atom Trapping on Ceria

In Situ Formation of Platinum-Carbon Catalysts in Propane Dehydrogenation

The catalytic production of propylene via propane dehydrogenation (PDH) is a key reaction in the chemical industry. By combining operando transmission electron microscopy with density functional theory analysis, we show that the intercalation and ordering of carbon on Pt interstitials to form Pt-C solid solutions is relevant for increasing propylene production. More specifically, we found that at the point of enhanced propylene formation, the structure of platinum nanoparticles is transformed into a transient caesium chloride-type Pt-C polymorph. At more elevated temperatures, the zincblende and rock salt polymorphs seemingly coexist. When propylene production was highest, multiple crystal structures consisting of Pt and carbon were occasionally found to coexist in one individual nanoparticle, distorting the Pt lattice. Catalyst coking was detected at all stages of the reaction, but did initially not affect all particles. These findings could lead to the development of novel synthesis strategies towards tailoring highly efficient PDH catalysts.

Structural Design of Single-Atom Catalysts for Enhancing Petrochemical Catalytic Reaction Process

Petroleum, as the "lifeblood" of industrial development, is the important energy source and raw material. The selective transformation of petroleum into high-end chemicals is of great significance, but still exists enormous challenges. Single-atom catalysts (SACs) with 100% atom utilization and homogeneous active sites, promise a broad application in petrochemical processes. Herein, the research systematically summarizes the recent research progress of SACs in petrochemical catalytic reaction, proposes the role of structural design of SACs in enhancing catalytic performance, elucidates the catalytic reaction mechanisms of SACs in the conversion of petrochemical processes, and reveals the high activity origins of SACs at the atomic scale. Finally, the key challenges are summarized and an outlook on the design, identification of active sites, and the appropriate application of artificial intelligence technology is provided for achieving scale-up application of SACs in petrochemical process.

Phase-Transition-Induced Surface Reconstruction of Rh1 Site in Intermetallic Alloy for Propane Dehydrogenation

The fine-tuning of the geometric and electronic structures of active sites plays a crucial role in catalysis. However, the intricate entanglement between the two aspects results in a lack of interpretable design for active sites, posing a challenge in developing high-performance catalysts. Here, we find that surface reconstruction induced by phase transition in intermetallic alloys enables synergistic geometric and electronic structure modulation, creating a desired active site microenvironment for propane dehydrogenation. The resulting electron-rich four-coordinate Rh1 site in the RhGe0.5Ga0.5 intermetallic alloy can accelerate the desorption of propylene and suppress the side reaction and thus exhibits a propylene selectivity of ∼98% with a low deactivation constant of 0.002 h-1 under propane dehydrogenation at 550 °C. Furthermore, we design a computational workflow to validate the rationality of the microenvironment modulation induced by the phase transition in an intermetallic alloy.

Tuning the Inorganic Core of a reduced Ni2Ge2 Cluster

Tetranuclear cores (M-E)2 of transition metals (M) and tetrylenes (EII=Si, Ge, Sn) are key motifs in homogeneous and heterogeneous catalysis. They exhibit a continuum of M-M and E-E bonding within the inorganic core that leads to a variety of structures for which there are no specific synthetic methods. Herein, we report a series of highly reduced [Ni0GeII]2 squares solely stabilized by bulky terphenyl (C6H3-2,6-Ar2) ligands, for which we provide complementary and high-yielding syntheses. Reactivity studies with common Lewis bases (carbene and CO) evince that the structure of the (M-E)2 core can be transformed. We have investigated this core modification by computational means, offering a rationale to better understand the continuum of bonding across these clusters.

Structured Catalysts and Catalytic Processes: Transport and Reaction Perspectives

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

Overcoming limitations in propane dehydrogenation by codesigning catalyst-membrane systems

Propylene production through propane dehydrogenation (PDH) is endothermic, and high temperatures required to achieve acceptable propane conversions lead to low selectivity and severe carbon-induced deactivation of conventional catalysts. We developed a catalyst-membrane system that removes the hydrogen by-product and can thus achieve propane conversions that exceed equilibrium limits. In this codesigned system, a silica/alumina (SiO2/Al2O3) hollow-fiber hydrogen membrane was packed with a selective platinum-tin (Pt1Sn1/SiO2) PDH catalyst on the tube side with hydrogen diffusing from the tube to the shell side. We demonstrate that the catalyst-membrane system can achieve propane conversions >140% of the nominal equilibrium conversion with a propylene selectivity >98% without deactivation of the system components. We also show that by introducing oxygen on the shell side of the catalyst-membrane system, we can couple the endothermic PDH reaction on the tube side with exothermic hydrogen oxidation on the shell side. This coupling results in higher rates of hydrogen transport, leading to further enhancements in the propane conversion as well as desired thermoneutral system operation.

Stable anchoring of single rhodium atoms by indium in zeolite alkane dehydrogenation catalysts

Maintaining the stability of single-atom catalysts in high-temperature reactions remains extremely challenging because of the migration of metal atoms under these conditions. We present a strategy for designing stable single-atom catalysts by harnessing a second metal to anchor the noble metal atom inside zeolite channels. A single-atom rhodium-indium cluster catalyst is formed inside zeolite silicalite-1 through in situ migration of indium during alkane dehydrogenation. This catalyst demonstrates exceptional stability against coke formation for 5500 hours in continuous pure propane dehydrogenation with 99% propylene selectivity and propane conversions close to the thermodynamic equilibrium value at 550°C. Our catalyst also operated stably at 600°C, offering propane conversions of >60% and propylene selectivity of >95%.

Efficient propane mineralization over unsaturated Pd cluster/CeO2 with prominent C-C cleavage capacity driven by inherent oxygen activation ability

Light alkanes extensively presented in industrial exhausts have led tremendous harm to the atmospheric environment and human health. However, the catalytic destruction of light alkanes generally operates at elevated temperatures and the consequent reaction by-products are inevitably produced. It is therefore of great significance to engineer catalysts with superior thermal stability, internal activity and selectivity. Herein, we developed a Pd cluster/CeO2 catalyst (Pdn/CeO2) by a scalable deposition precipitation strategy, which demonstrates unexpected activity and thermal stability in the presence of 5% H2O attributing to abundant unsaturated Pd metal sites and excellent oxygen dissociation performance. Pdn/CeO2 possesses a highly efficient C-C cleavage capability due to the persistent formation of a large number of oxygen vacancies. In comparison, the Pd1/CeO2 catalyst, which is preferential for C-H bond cleavage and inactive for C-C bond cracking, produces remarkable hazardous organic by-products such as propyne and propylene, inhibiting the continuous decomposition of propane. The present study sheds critical insights into engineering efficient and stable catalysts for light alkane destruction.

Amorphous CeOx Islands on Dealuminated Zeolite Beta to Stabilize Pt Nanoparticles as Efficient and Antisintering Catalysts for Propane Dehydrogenation

Pt-based catalysts have been widely used in propane dehydrogenation due to their superior activation of C-H bonds and weak scission of C-C bonds. However, in the process of repeated calcination to remove deposited coke, the active Pt species tend to sinter, resulting in a significant decline in catalytic activity. In this study, amorphous CeOx islands loaded on dealuminated Beta zeolite were prepared via simple wetness impregnation. Then, partially embedded Pt nanoparticles in CeOx islands were obtained after reduction owing to the affinity of CeOx for Pt. In the propane dehydrogenation reaction, Pt/Ce5-SiBeta with a Ce loading of 4.55 wt % and Pt loading of 0.72 wt % exhibited the highest activity and the lowest inactivation constant at 550 °C. More importantly, due to the anchoring effect of CeOx on Pt, the catalytic activity of Pt could be recovered after a simple calcination-reduction regeneration process, avoiding the chlorination treatment for the redispersion of Pt species used in industry. In addition, to improve the selectivity of the Pt/Ce5-SiBeta catalyst, a PtSn/Ce5-SiBeta catalyst with excellent activity, selectivity, and recycling stability has been prepared by introducing Sn into Pt/Ce5-SiBeta. The use of amorphous CeOx islands to improve the sintering resistance of Pt opens up new prospects for the design of stable industrial dehydrogenation catalysts.

The Role of In Situ/Operando IR Spectroscopy in Unraveling Adsorbate-Induced Structural Changes in Heterogeneous Catalysis

Heterogeneous catalysts undergo thermal- and/or adsorbate-induced dynamic changes under reaction conditions, which consequently modify their catalytic behavior. Hence, it is increasingly crucial to characterize the properties of a catalyst under reaction conditions through the so-called "operando" approach. Operando IR spectroscopy is probably one of the most ubiquitous and versatile characterization methods in the field of heterogeneous catalysis, but its potential in identifying adsorbate- and thermal-induced phenomena is often overlooked in favor of other less accessible methods, such as XAS spectroscopy and high-resolution microscopy. Without detracting from these techniques, and while aware of the enormous value of a multitechnique approach, the purpose of this Review is to show that IR spectroscopy alone can provide relevant information in this field. This is done by discussing a few selected case studies from our own research experience, which belong to the categories of both "single-site"- and nanoparticle-based catalysts.

Restructuring of titanium oxide overlayers over nickel nanoparticles during catalysis

Reducible supports can affect the performance of metal catalysts by the formation of suboxide overlayers upon reduction, a process referred to as the strong metal-support interaction (SMSI). A combination of operando electron microscopy and vibrational spectroscopy revealed that thin TiO_x overlayers formed on nickel/titanium dioxide catalysts during 400°C reduction were completely removed under carbon dioxide hydrogenation conditions. Conversely, after 600°C reduction, exposure to carbon dioxide hydrogenation reaction conditions led to only partial reexposure of nickel, forming interfacial sites in contact with TiO_x and favoring carbon-carbon coupling by providing a carbon species reservoir. Our findings challenge the conventional understanding of SMSIs and call for more-detailed operando investigations of nanocatalysts at the single-particle level to revisit static models of structure-activity relationships.

Time-Resolved Formation and Operation Maps of Pd Catalysts Suggest a Key Role of Single Atom Centers in Cross-Coupling

An approach to the spatially localized characterization of supported catalysts over a reaction course is proposed. It consists of a combination of scanning, transmission, and high-resolution scanning transmission electron microscopy to determine metal particles from arrays of surface nanoparticles to individual nanoparticles and individual atoms. The study of the evolution of specific metal catalyst particles at different scale levels over time, particularly before and after the cross-coupling catalytic reaction, made it possible to approach the concept of 4D catalysis-tracking the positions of catalytic centers in space (3D) over time (+1D). The dynamic behavior of individual palladium atoms and nanoparticles in cross-coupling reactions was recorded with nanometer accuracy via the precise localization of catalytic centers. Single atoms of palladium leach out into solution from the support under the action of the catalytic system, where they exhibit extremely high catalytic activity compared to surface metal nanoparticles. Monoatomic centers, which make up only approximately 1% of palladium in the Pd/C system, provide more than 99% of the catalytic activity. The remaining palladium nanoparticles changed their shape and could move over the surface of the support, which was recorded by processing images of the array of nanoparticles with a neural network and aligning them using automatically detected keypoints. The study reveals a novel opportunity for single-atom catalysis─easier detachment (capture) from (on) the carbon support surface is the origin of superior catalytic activity, rather than the operation of single atomic catalytic centers on the surface of the support, as is typically assumed.

Illustrating new understanding of adsorbed water on silica for inducing tetrahedral cobalt(II) for propane dehydrogenation

Highly dispersed metal sites on the surface of silica, achieved from immobilization of metal precursor within hydroxyl groups, has gained increasing attention in the field of heterogeneous catalyst. However, the special role of adsorbed water derived by hydroxyl groups on the silica is generally ignored. Herein, a new understanding of adsorbed water on the formation of highly dispersed tetrahedral Co(II) (T_d-cobalt(II)) sites is illustrated. It is indicated that sufficient adsorbed water induces the transformation of precursor of Co(NO₃)₂ into intermediate of [Co(H₂O)₆]²⁺. Subsequently, [Co(H₂O)₆]²⁺ makes the highly dispersed T_d-cobalt(II) sites to be available during direct H₂-reduction process. A systematic characterization and DFT calculation prove the existence of the adsorbed water and the importance of the intermediate of [Co(H₂O)₆]²⁺, respectively. The as-synthesized catalyst is attempted to the propane dehydrogenation, which shows better reactivity when compared with other reported Co based catalysts.

Design of Single-Atom Catalysts and Tracking Their Fate Using Operando and Advanced X-ray Spectroscopic Tools

The potential of operando X-ray techniques for following the structure, fate, and active site of single-atom catalysts (SACs) is highlighted with emphasis on a synergetic approach of both topics. X-ray absorption spectroscopy (XAS) and related X-ray techniques have become fascinating tools to characterize solids and they can be applied to almost all the transition metals deriving information about the symmetry, oxidation state, local coordination, and many more structural and electronic properties. SACs, a newly coined concept, recently gained much attention in the field of heterogeneous catalysis. In this way, one can achieve a minimum use of the metal, theoretically highest efficiency, and the design of only one active site-so-called single site catalysts. While single sites are not easy to characterize especially under operating conditions, XAS as local probe together with complementary methods (infrared spectroscopy, electron microscopy) is ideal in this research area to prove the structure of these sites and the dynamic changes during reaction. In this review, starting from their fundamentals, various techniques related to conventional XAS and X-ray photon in/out techniques applied to single sites are discussed with detailed mechanistic and in situ/operando studies. We systematically summarize the design strategies of SACs and outline their exploration with XAS supported by density functional theory (DFT) calculations and recent machine learning tools.

Recent progresses on single-atom catalysts for the removal of air pollutants

The booming industrialization has aggravated emission of air pollutants, inflicting serious harm on environment and human health. Supported noble-metals are one of the most popular catalysts for the oxidation removal of air pollutants. Unfortunately, the high price and large consumption restrict their development and practical application. Single-atom catalysts (SACs) emerge and offer an optimizing approach to address this issue. Due to maximal atom utilization, tunable coordination and electron environment and strong metal-support interaction, SACs have shown remarkable catalytic performance on many reactions. Over the last decade, great potential of SACs has been witnessed in the elimination of air pollutants. In this review, we first briefly summarize the synthesis methods and modulation strategies together with the characterization techniques of SACs. Next, we highlight the application of SACs in the abatement of air pollutants including CO, volatile organic compounds (VOCs) and NOx, unveiling the related catalytic mechanism of SACs. Finally, we propose the remaining challenges and future perspectives of SACs in fundamental research and practical application in the field of air pollutant removal.

Dendritic Mesoporous Silica Nanoparticle Supported PtSn Catalysts for Propane Dehydrogenation

PtSn catalysts were synthesized by incipient-wetness impregnation using a dendritic mesoporous silica nanoparticle support. The catalysts were characterized by XRD, N2 adsorption–desorption, TEM, XPS and Raman, and their catalytic performance for propane dehydrogenation was tested. The influences of Pt/Sn ratios were investigated. Changing the Pt/Sn ratios influences the interaction between Pt and Sn. The catalyst with a Pt/Sn ratio of 1:2 possesses the highest interaction between Pt and Sn. The best catalytic performance was obtained for the Pt1Sn2/DMSN catalyst with an initial propane conversion of 34.9%. The good catalytic performance of this catalyst is ascribed to the small nanoparticle size of PtSn and the favorable chemical state and dispersion degree of Pt and Sn species.

The Progress and Outlook of Metal Single-Atom-Site Catalysis

Single-atom-site catalysts (SASCs) featuring maximized atom utilization and isolated active sites have progressed tremendously in recent years as a highly prosperous branch of catalysis research. Varieties of SASCs have been developed that show excellent performance in many catalytic applications. The major goal of SASC research is to establish feasible synthetic strategies for the preparation of high-performance catalysts, to achieve an in-depth understanding of the active-site structures and catalytic mechanisms, and to develop practical catalysts with industrial value. This Perspective describes the up-to-date development of SASCs and related catalysts, such as dual-atom-site catalysts (DASCs) and nano-single-atom-site catalysts (NSASCs), analyzes the current challenges encountered by these catalysts for industrial applications, and proposes their possible future development path.

Catalysis of Alloys: Classification, Principles, and Design for a Variety of Materials and Reactions

Alloying has long been used as a promising methodology to improve the catalytic performance of metallic materials. In recent years, the field of alloy catalysis has made remarkable progress with the emergence of a variety of novel alloy materials and their functions. Therefore, a comprehensive disciplinary framework for catalytic chemistry of alloys that provides a cross-sectional understanding of the broad research field is in high demand. In this review, we provide a comprehensive classification of various alloy materials based on metallurgy, thermodynamics, and inorganic chemistry and summarize the roles of alloying in catalysis and its principles with a brief introduction of the historical background of this research field. Furthermore, we explain how each type of alloy can be used as a catalyst material and how to design a functional catalyst for the target reaction by introducing representative case studies. This review includes two approaches, namely, from materials and reactions, to provide a better understanding of the catalytic chemistry of alloys. Our review offers a perspective on this research field and can be used encyclopedically according to the readers' individual interests.

Thermally-stable single-atom catalysts and beyond: A perspective

Single-atom catalysis is a research Frontier and has attracted extensive interests in catalysis. Significant progresses have been carried out in the synthesis and characterization of metal single-atom catalysts (SACs). However, the stability and catalytic reactivity of metal SAC at elevated temperatures are not well documented because single atoms sinter at elevated temperatures. Therefore, the development of stable and reactive SAC at high temperatures remains a formidable challenge. In this perspective, we summarize recent efforts on the preparation of the thermally-stable SACs synthesized at elevated temperature via the reverse-Ostwald ripening mechanism, including the approaches of atom trapping and vapor-phase self-assembly. The reducibility of lattice oxygen, the loading upper limit and the location of the metal single atom are discussed, combining experiments with simulations. In addition, we demonstrate that the coordination structure of the metal single atom can be tailored to address the relationship of structure and performances of the metal SAC in reactions. We expect that this perspective can provide some insights to guide the study for the rational design of thermally-stable and active single atom catalysts, which are especially suitable for high-temperature reactions.

Solid-State Reaction Synthesis of Nanoscale Materials: Strategies and Applications

Nanomaterials (NMs) with unique structures and compositions can give rise to exotic physicochemical properties and applications. Despite the advancement in solution-based methods, scalable access to a wide range of crystal phases and intricate compositions is still challenging. Solid-state reaction (SSR) syntheses have high potential owing to their flexibility toward multielemental phases under feasibly high temperatures and solvent-free conditions as well as their scalability and simplicity. Controlling the nanoscale features through SSRs demands a strategic nanospace-confinement approach due to the risk of heat-induced reshaping and sintering. Here, we describe advanced SSR strategies for NM synthesis, focusing on mechanistic insights, novel nanoscale phenomena, and underlying principles using a series of examples under different categories. After introducing the history of classical SSRs, key theories, and definitions central to the topic, we categorize various modern SSR strategies based on the surrounding solid-state media used for nanostructure growth, conversion, and migration under nanospace or dimensional confinement. This comprehensive review will advance the quest for new materials design, synthesis, and applications.

Tailoring Single-Atom Platinum for Selective and Stable Catalysts in Propane Dehydrogenation

Propane dehydrogenation has been a promising method for producing propylene that has the potentials to meet the increasing global demand for propylene. However, owing to the restricted equilibrium conversion caused by the high endothermicity, even the Pt-based catalysts, which exhibit high activity and selectivity, severely suffer significantly from coke formation and/or nanoparticle sintering at realistic reaction temperatures, resulting in a short catalyst lifetime. As a result, few innovative catalysts in terms of catalytic activity, selectivity, and stability, have been produced. In this Review, we focus on the characteristics of single-atom-like Pt sites for PDH and attempt to provide suggestions for developing highly efficient catalysts. First, we briefly describe the fundamental strategies. Following that, the remarkable catalysis is addressed by three different distinct sorts of state-of-the-art single-atom-like Pt catalysts are discussed. Additionally, we present other promising catalyst design approaches that are not based on single-atom-like Pt catalysts, as well as future research challenges in this field.

Nonoxidative Coupling of Methane over Ceria-Supported Single-Atom Pt Catalysts in DBD Plasma

Plasma-catalytic direct nonoxidative coupling of methane (NCM) into C₂ hydrocarbons was investigated over ceria-supported atomically dispersed Pt (Pt/CeO₂-SAC) and nanoparticle Pt (Pt/CeO₂-NP) catalysts in dielectric barrier discharge (DBD) plasma. Nonthermal plasma facilitated C-H bond dissociation in CH₄ at low temperatures (<150 °C) and atmospheric pressure. The presence of Pt/CeO₂ catalysts in plasma further enhanced CH₄ conversion and C₂ hydrocarbon selectivity by enabling the conversion of vibrationally excited methane species with high internal energy on active Pt sites. Noticeably, the Pt/CeO₂-SAC catalyst displayed a more remarkable performance, with a CH₄ conversion of 39% and a C₂ selectivity of 54% at 54 W. The enhanced CH₄ conversion was attributed to abundant coordinatively unsaturated Pt sites in Pt/CeO₂-SAC, which were more active for C-H bond scission. Meanwhile, isolated Pt atoms in Pt/CeO₂-SAC promoted C₂ hydrocarbon formation by hindering the unselective formation of coke from deep dehydrogenation of CH_x^• intermediates and higher hydrocarbons from oligomerization reactions.

CeO2-Promoted PtSn/SiO2 as a High-Performance Catalyst for the Oxidative Dehydrogenation of Propane with Carbon Dioxide

The oxidative dehydrogenation of propane with CO₂ (CO₂-ODP) has been extensively investigated as a promising green technology for the efficient production of propylene, but the lack of a high-performance catalyst is still one of the main challenges for its industrial application. In this work, an efficient catalyst for CO₂-ODP was developed by adding CeO₂ to PtSn/SiO₂ as a promoter via the simple impregnation method. Reaction results indicate that the addition of CeO₂ significantly improved the catalytic activity and propylene selectivity of the PtSn/SiO₂ catalyst, and the highest space-time yield of 1.75 g(C₃H₆)·g(catalyst)^-1·h^-1 was achieved over PtSn/SiO₂ with a Ce loading of 6 wt%. The correlation of the reaction results with the characterization data reveals that the introduction of CeO₂ into PtSn/SiO₂ not only improved the Pt dispersion but also regulated the interaction between Pt and Sn species. Thus, the essential reason for the promotional effect of CeO₂ on CO₂-ODP performance was rationally ascribed to the enhanced adsorption of propane and CO₂ originating from the rich oxygen defects of CeO₂. These important understandings are applicable in further screening of promoters for the development of a high-performance Pt-based catalyst for CO₂-ODP.

Molecular Stabilization of Sub-Nanometer Cu Clusters for Selective CO2 Electromethanation

Electrochemical CO₂ methanation powered by renewable electricity provides a promising approach to utilizing CO₂ in the form of a high-energy-density, clean fuel. Cu nanoclusters have been predicted by theoretical calculations to improve methane selectivity. Direct electrochemical reduction of Cu-based metal-organic frameworks (MOFs) results in large-size Cu nanoparticles which favor multi-carbon products. This study concerns an electrochemical oxidation-reduction method to prepare Cu clusters from MOFs. The derived Cu clusters exhibit a faradaic efficiency of 51.2 % for CH₄ with a partial current density of >150 mA cm^-2 . High-resolution microscopy, in situ X-ray absorption spectroscopy, in situ Raman spectroscopy, and a range of ex situ spectroscopies indicate that the distinctive CH₄ selectivity is due to the sub-nanometer size of the derived materials, as well as stabilization of the clusters by residual ligands of the pristine MOF. This work offers a new insight into steering product selectivity of Cu by an electrochemical processing method.

Cu/O Frustrated Lewis Pairs on Cu Doped CeO2(111) for Acetylene Hydrogenation: A First-Principles Study

In this work, the H2 dissociation and acetylene hydrogenation on Cu doped CeO2(111) were studied using density functional theory calculations. The results indicated that Cu doping promotes the formation of oxygen vacancy (Ov) which creates Cu/O and Ce/O frustrated Lewis pairs (FLPs). With the help of Cu/O FLP, H2 dissociation can firstly proceed via a heterolytic mechanism to produce Cu-H and O-H by overcoming a barrier of 0.40 eV. The H on Cu can facilely migrate to a nearby oxygen to form another O-H species with a barrier of 0.43 eV. The rate-determining barrier is lower than that for homolytic dissociation of H2 which produces two O-H species. C2H2 hydrogenation can proceed with a rate-determining barrier of 1.00 eV at the presence of Cu-H and O-H species., While C2H2 can be catalyzed by two O-H groups with a rate-determining barrier of 1.06 eV, which is significantly lower than that (2.86 eV) of C2H2 hydrogenated by O-H groups on the bare CeO2(111), showing the high activity of Cu doped CeO2(111) for acetylene hydrogenation. In addition, the rate-determining barrier of C2H4 further hydrogenated by two O-H groups is 1.53 eV, much higher than its desorption energy (0.72 eV), suggesting the high selectivity of Cu doped CeO2(111) for C2H2 partial hydrogenation. This provides new insights to develop effective hydrogenation catalysts based on metal oxide.

Support Stabilized PtCu Single-atom Alloys for Propane Dehydrogenation

PtCu single-atom alloys (SAAs) open an extensive prospect for heterogeneous catalysis. However, as the host of SAAs, Cu suffers from severe sintering at elevated temperature, resulting in poor stability of catalysts. This paper describes the suppression of the agglomeration of Cu nanoparticles under high temperature conditions using copper phyllosilicate (CuSiO₃) as the support of PtCu SAAs. Based on quasi in situ XPS, in situ CO-DRIFTS, in situ Raman spectroscopy and in situ XRD, we demonstrated that the interfacial Cu⁺–O–Si formed upon reduction at 680 °C serves as the adhesive between Cu nanoparticles and the silicon dioxide matrix, strengthening the metal–support interaction. Consequently, the resistance to sintering of PtCu SAAs was improved, leading to high catalytic stability during propane dehydrogenation without sacrificing conversion and selectivity. The optimized PtCu SAA catalyst achieved more than 42% propane conversion and 93% propylene selectivity at 580 °C for at least 30 hours. It paves a way for the design and development of highly active supported single-atom alloy catalysts with excellent thermal stability.

This paper describes PtCu single-atom alloys supported on copper phyllosilicate via Cu⁺–O–Si. The catalyst exhibits sintering resistance in propane dehydrogenation reaction without sacrificing activity and selectivity.

Thermally Stable Single-Atom Heterogeneous Catalysts

Single-atom catalysts (SACs) have attracted extensive attention in fields related to energy, environment, and material sciences because of the high atom efficiency and the unique properties of these materials. Many approaches have hitherto been successfully established to prepare SACs, including impregnation, pyrolysis-involved processes, atom trapping, and coprecipitation. However, under typical reaction conditions, single atoms on catalysts tend to migrate or agglomerate, forming nanoclusters or nanoparticles, which lowers their surface free energy. Efforts are required to develop strategies for improving the thermal stability of SACs while achieving excellent catalytic performance. In this Progress Report, recent advances in the development of thermally durable single-atom heterogeneous catalysts are discussed. Several important preparation approaches for thermally stable SACs are described in this article. Fundamental understanding of the coordination structures of thermally stable single atom prepared by these methods is discussed. Furthermore, the catalytic performances of these thermally stable SACs are reviewed, including their activity and stability. Finally, a perspective of this important and rapidly evolving research field is provided.

Atomically dispersed metal catalysts on nanodiamond and its derivatives: synthesis and catalytic application

Atomically dispersed metal catalysts (ADMCs) have attracted increasing interest in the field of heterogeneous catalysis. As sub-nanometric catalysts, ADMCs have exhibited remarkable catalytic performance in many reactions. ADMCs are classified into two categories: single atom catalysts (SACs) and atomically dispersed clusters with a few atoms. To stabilize the highly active ADMCs, nanodiamond (ND) and its derivatives (NDDs) are promising supports. In this Feature Article, we have introduced the advantages of NDDs with a highly curved surface and tunable surface properties. The controllable defective sites and oxygen functional groups are known as the anchoring sites for ADMCs. Tunable surface acid-base properties enable ADMCs supported on NDDs to exhibit unique selectivity towards target products and an extended lifetime in many reactions. In addition, we have firstly overviewed the recent advances in the synthesis strategies for effectively fabricating ADMCs on NDDs, and further discussed how to achieve the atomic dispersion of metal precursors and stabilize the as-formed metal atoms against migration and agglomeration based on NDDs. And then, we have also systematically summarized the advantages of ADMCs supported on NDDs in reactions, including hydrogenation, dehydrogenation, aerobic oxidation and electrochemical reaction. These reactions can also effectively guide the design of ADMCs. The recent progress in understanding the effect of structure of active centers and metal-support interactions (MSIs) on the catalytic performance of ADMCs is particularly highlighted. At last, the possible research directions in ADMCs are forecasted.