Changes in Catalytic and Adsorptive Properties of 2 nm Pt3Mn Nanoparticles by Subsurface Atoms

Distorted Surface Ensembles in Platinum-Antimony for the Durable Catalytic Dehydrogenation of Methylcyclohexane

Geometric and electronic effects are particularly pronounced when catalyzing small molecules, which require small active-metal ensembles. Researchers have been intensively focused on the alloy catalysis of small molecules. However, when large molecules are catalyzed, large active-metal ensembles are preferable to small active-metal ensembles. The catalysis with large ensembles in alloys proceeds more efficiently than that with pure metals because of the geometric and electronic effects of diluent metals. However, it is difficult to significantly improve the catalytic performance because of the limited changes in the geometric and electronic features in active-metal-rich compositions. Thus, we employed distorted active-metal ensembles, which are expected to have unique adsorptivity/reactivity for large molecules. We found that the unique crystal structure of Pt3Sb showed distorted Pt3 ensembles shaped as isosceles triangles, which differ from the standard Pt3 ensembles shaped as regular triangles. We used methylcyclohexane dehydrogenation as a proof-of-concept reaction, which shows that the feature of Pt3 ensembles is crucial for catalytic performance. Theoretical and experimental results revealed that the distorted Pt3@Pt3Sb catalyst effectively suppressed the side reactions and exhibited considerably higher durability than the standard Pt3 ensembles, represented by the Pt3@Pt3Sn catalyst, highlighting the importance of the Pt3 shape.

Progressive Fabrication of a Pt-Based High-Entropy-Alloy Catalyst toward Highly Efficient Propane Dehydrogenation

High-entropy alloys (HEAs) have emerged as burgeoning heterogeneous catalysts due to their vast material space, unique structure, and superior stability. However, the dominant trial-and-error approaches hamper the exploration of efficient catalysts, necessitating the development of rational design strategies. Here, we report a progressive approach to the design and fabrication of HEA catalysts guided by alloying effects toward propane dehydrogenation. Cu, Sn, Au, and Pd are selected and demonstrated to induce dilution, encapsulation, surface enrichment, and inhomogeneity effects on Pt. The fabricated HEA, PtCuSnAuPd/SiO2, exhibits excellent activity, selectivity, and stability. The propylene formation rates reach 256 and 390 molC3H6 gPt -1 h-1 at 550 and 600 °C, respectively. Systematic characterizations reveal that the random elemental mixing, structural stability, and high Pt exposure promote the exposure of abundant stable isolated Pt sites. This work comprehensively explores the rational design and fabrication of HEA catalysts from a unique perspective, offering opportunities for developing advanced catalysts.

Metal nanoparticles encapsulation within multi-shell spongy-core porous microspheres for efficient tandem catalysis

The "one-pot" cascade process involves multiple catalytic conversions followed by a single workup stage. This method has the capability to optimize catalytic efficiency by reducing chemical processes. The key to achieving cascade reactions lies in designing cascade catalysts with well-dispersed, stably immobilized, and accessible noble metal nanoparticles for multiple catalytic conversions. This work presents a strategy for creating long-lasting cascade catalysts by encapsulating Ru and Pd nanoparticles within multi-shell spongy-core porous microspheres (MS-SC-PMs). This cascade catalyst strategy enables the continuous hydrogenation of nitrobenzene to aniline and further to cyclohexylamine, demonstrating both high selectivity and conversion rates. Notably, this approach overcomes the typical challenges associated with noble metal nanoparticles, such as poor stability and recyclability, as it maintains its performance over ten consecutive cycles. Additionally, the MS-SC-PMs have the versatility to encapsulate various metal nanoparticles, providing catalytic versatility, scalability, and a promising avenue for designing long-lasting catalysts loaded with nanoparticles.

Plasma-Catalyst Dynamics: Nonthermal Activation of Strong Metal-Support Interactions

Nonthermal plasma-surface interactions enable transformative advancements in green chemistry, healthcare, materials processing, pollution abatement, and the ever-growing area of plasma catalysis. In the context of plasma catalysis, the fate of the active sites during plasma treatment has remained enigmatic, and observation of low-temperature plasma-catalyst events has been challenging. The induction of strong metal-support interactions (SMSI) through high-temperature hydrogen treatment is a well-documented and established, yet limited, method to impact selectivity and stability of noble metal catalysts on reducible supports. Thermally driven SMSI occurs through reduction and subsequent migration of the support to the surface of exposed metal sites, thus affecting the catalyst both electronically and geometrically and serving as an ideal system to evaluate dynamic plasma-catalyst interactions. In this study, a dielectric barrier discharge of hydrogen was used to successfully induce a plasma-SMSI state (P-SMSI) in niobia-supported platinum particles at bulk-gas temperatures as low as -30 °C, which enhances the selectivity for propane dehydrogenation and offers conclusive evidence of plasma-catalyst interactions. Time-resolved spectroscopic evidence of this phenomenon was obtained in situ using a cryogenically cooled plasma IR transmission cell, which provided evidence of diffusion-controlled surface migration. Collectively, P-SMSI constitutes a promising, low-impact technology for synthesizing SMSI-enhanced catalysts with controllable active sites, and knowledge of the nonthermal plasma-catalyst dynamics is critical in designing materials for specific applications or selecting conditions of operation.

Pt-ZnOx Interfacial Effect on the Performance of Propane Dehydrogenation and Mechanism Study

Bimetallic Pt-based catalysts, for example, PtZn and PtSn catalysts, have gained significant attention for addressing the poor stability and low selectivity of pristine Pt catalysts over propane dehydrogenation (PDH). However, the structures of the active sites and the corresponding catalytic mechanism of PDH are still elusive. Here, we demonstrate a spatially confined Pt-ZnmOx@RUB-15 catalyst (where "m" is the mole ratio of Zn/Pt and RUB-15 is a layered silica), which exhibited high catalytic activity, ultrahigh selectivity (>99%), and resistance to coking at 550 °C for PDH. Significantly different from the preliminary studies over the PtZn catalysts, through the assistance of quasi-in situ X-ray photoelectron spectroscopy (XPS), in situ Fourier transform infrared spectroscopy (CO-FTIR), in situ X-ray absorption spectroscopy (XAS), and CO titration, we discovered that the active sites for PDH were the Pt-ZnOx interfaces, characterized by a structure of Ptδ+-Zn2+-O-Si. Density functional theory (DFT) calculations showed that Pt atoms positioned at Pt-ZnOx interfaces with coordinatively unsaturated ZnOx sites facilitate the C-H bond breaking of propane while concurrently suppressing deep dehydrogenation processes. This study suggests that engineering the interfaces of Pt-metal oxides under spatially confined conditions holds promise for developing highly efficient Pt-based catalysts for light alkane dehydrogenation.

Screening and Mechanism Exploration of Non-Noble Metal Ni3M Catalysts for Propane Dehydrogenation: The Excellence of Synergistic Effects

The development of cost-effective and anti-coking catalysts for propane dehydrogenation (PDH) is crucial. Here, non-noble metal-incorporated Ni-based catalysts (Ni3M, M = Sc, Ti, V, Mn, Fe, Co, Cu, Zn, Ga, Zr, Nb, Mo, In, Sn) were employed in the PDH process. The introduction of V, Nb, and Mo, with their strong carbon binding ability, created unique Ni-M cooperative sites, enhancing the catalytic performance. Other non-noble metals influenced the electronic structure of Ni, affecting the overall catalytic behavior. V and Nb exhibited a balanced combination of activity, selectivity, and stability, making them potential catalyst candidates. Microkinetic simulations revealed that Ni3V and Ni3Nb displayed high selectivity toward olefins with low apparent activation energies. This study emphasizes the significance of bimetallic synergy in enhancing PDH performance and provides new directions for the development of efficient alkane dehydrogenation catalyst development.

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.

Pt Nanoparticle-Mn Single-Atom Pairs for Enhanced Oxygen Reduction

The intrinsic roadblocks for designing promising Pt-based oxygen reduction reaction (ORR) catalysts emanate from the strong scaling relationship and activity-stability-cost trade-offs. Here, a carbon-supported Pt nanoparticle and a Mn single atom (PtNP-MnSA/C) as in situ constructed PtNP-MnSA pairs are demonstrated to be an efficient catalyst to circumvent the above seesaws with only ∼4 wt % Pt loadings. Experimental and theoretical investigations suggest that MnSA functions not only as the "assist" for Pt sites to cooperatively facilitate the dissociation of O2 due to the strong electronic polarization, affording the dissociative pathway with reduced H2O2 production, but also as an electronic structure "modulator" to downshift the d-band center of Pt sites, alleviating the overbinding of oxygen-containing intermediates. More importantly, MnSA also serves as a "stabilizer" to endow PtNP-MnSA/C with excellent structural stability and low Fenton-like reactivity, resisting the fast demetalation of metal sites. As a result, PtNPs-MnSA/C shows promising ORR performance with a half-wave potential of 0.93 V vs reversible hydrogen electrode and a high mass activity of 1.77 A/mgPt at 0.9 V in acid media, which is 19 times higher than that of commercial Pt/C and only declines by 5% after 80,000 potential cycles. Specifically, PtNPs-MnSA/C reaches a power density of 1214 mW/cm2 at 2.87 A/cm2 in an H2-O2 fuel cell.

Intermetallic Nanocrystals for Fuel-Cells-Based Electrocatalysis

Electrocatalysis underpins the renewable electrochemical conversions for sustainability, which further replies on metallic nanocrystals as vital electrocatalysts. Intermetallic nanocrystals have been known to show distinct properties compared to their disordered counterparts, and been long explored for functional improvements. Tremendous progresses have been made in the past few years, with notable trend of more precise engineering down to an atomic level and the investigation transferring into more practical membrane electrode assembly (MEA), which motivates this timely review. After addressing the basic thermodynamic and kinetic fundamentals, we discuss classic and latest synthetic strategies that enable not only the formation of intermetallic phase but also the rational control of other catalysis-determinant structural parameters, such as size and morphology. We also demonstrate the emerging intermetallic nanomaterials for potentially further advancement in energy electrocatalysis. Then, we discuss the state-of-the-art characterizations and representative intermetallic electrocatalysts with emphasis on oxygen reduction reaction evaluated in a MEA setup. We summarize this review by laying out existing challenges and offering perspective on future research directions toward practicing intermetallic electrocatalysts for energy conversions.

Ultrasmall PtMn nanoparticles as sensitive manganese release modulator for specificity cancer theranostics

Manganese-based nanomaterials (Mn-nanomaterials) hold immense potential in cancer diagnosis and therapies. However, most Mn-nanomaterials are limited by the low sensitivity and low efficiency toward mild weak acidity (pH 6.4-6.8) of the tumor microenvironment, resulting in unsatisfactory therapeutic effect and poor magnetic resonance imaging (MRI) performance. This study introduces pH-ultrasensitive PtMn nanoparticles as a novel platform for enhanced ferroptosis-based cancer theranostics. The PtMn nanoparticles were synthesized with different diameters from 5.3 to 2.7 nm with size-dominant catalytic activity and magnetic relaxation, and modified with an acidity-responsive polymer to create pH-sensitive agents. Importantly, R-PtMn-1 (3 nm core) presents "turn-on" oxidase-like activity, affording a significant enhancement ratio (pH 6.0/pH 7.4) in catalytic activity (6.7 folds), compared with R-PtMn-2 (4.2 nm core, 3.7 folds) or R-PtMn-3 (5.3 nm core, 2.1 folds), respectively. Moreover, R-PtMn-1 exhibits dual-mode contrast in high-field MRI. R-PtMn-1 possesses a good enhancement ratio (pH 6.4/pH 7.4) that is 3 or 3.2 folds for T1- or T2-MRI, respectively, which is higher than that of R-PtMn-2 (1.4 or 1.5 folds) or R-PtMn-3 (1.1 or 1.2 folds). Moreover, their pH-ultrasensitivity enabled activation specifically within the tumor microenvironment, avoiding off-target toxicity in normal tissues during delivery. In vitro studies demonstrated elevated intracellular reactive oxygen species production, lipid peroxidation, mitochondrial membrane potential changes, malondialdehyde content, and glutathione depletion, leading to enhanced ferroptosis in cancer cells. Meanwhile, normal cells remained unaffected by the nanoparticles. Overall, the pH-ultrasensitive PtMn nanoparticles offer a promising strategy for accurate cancer diagnosis and ferroptosis-based therapy.

Ti-Doping in Silica-Supported PtZn Propane Dehydrogenation Catalysts: From Improved Stability to the Nature of the Pt-Ti Interaction

Propane dehydrogenation is an important industrial reaction to access propene, the world's second most used polymer precursor. Catalysts for this transformation are required to be long living at high temperature and robust toward harsh oxidative regeneration conditions. In this work, combining surface organometallic chemistry and thermolytic molecular precursor approach, we prepared well-defined silica-supported Pt and alloyed PtZn materials to investigate the effect of Ti-doping on catalytic performances. Chemisorption experiments and density functional calculations reveal a significant change in the electronic structure of the nanoparticles (NPs) due to the Ti-doping. Evaluation of the resulting materials PtZn/SiO₂ and PtZnTi/SiO₂ during long deactivation phases reveal a stabilizing effect of Ti in PtZnTi/SiO₂ with a k_d of 0.015 h^-1 compared to PtZn/SiO₂ with a k_d of 0.022 h^-1 over 108 h on stream. Such a stabilizing effect is also present during a second deactivation phase after applying a regeneration protocol to the materials under O₂ and H₂ at high temperatures. A combined scanning transmission electron microscopy, in situ X-ray absorption spectroscopy, electron paramagnetic resonance, and density functional theory study reveals that this effect is related to a sintering prevention of the alloyed PtZn NPs in PtZnTi/SiO₂ due to a strong interaction of the NPs with Ti sites. However, in contrast to classical strong metal-support interaction, we show that the coverage of the Pt NPs with TiO_x species is not needed to explain the changes in adsorption and reactivity properties. Indeed, the interaction of the Pt NPs with Ti^III sites is enough to decrease CO adsorption and to induce a red-shift of the CO band because of electron transfer from the Ti^III sites to Pt⁰.

Efficient Screening of Metal Promoters of Pt Catalysts for C-H Bond Activation in Propane Dehydrogenation from a Combined First-Principles Calculations and Machine-Learning Study

Platinum-based materials are the most widely used catalysts in propane direct dehydrogenation, which could achieve a balanced activity between both propane conversion and propene formation. One of the core issues of Pt catalysts is how to efficiently activate the strong C-H bond. It has been suggested that adding second metal promoters could greatly solve this problem. In the current work, first-principles calculations combined with machine learning are performed in order to obtain the most promising metal promoters and identify key descriptors for control performance. The combination of three different modes of adding metal promoters and two ratios between promoters and platinum sufficiently describes the system under investigation. The activity of propane activation and the formation of propene are reflected by the increase or decrease of the adsorption energy and C-H bond activation of propane and propene after the addition of promoters. The data of adsorption energy and kinetic barriers from first-principles calculations are streamed into five machine-learning methods including gradient boosting regressor (GBR), K neighbors regressor (KNR), random forest regressor (RFR), and AdaBoost regressor (ABR) together with the sure independence screening and sparsifying operator (SISSO). The metrics (RMSE and R²) from different methods indicated that GBR and SISSO have the most optimal performance. Furthermore, it is found that some descriptors derived from the intrinsic properties of metal promoters can determine their properties. In the end, Pt₃Mo is identified as the most active catalyst. The present work not only provides a solid foundation for optimizing Pt catalysts but also provides a clear roadmap to screen metal alloy catalysts.

Designing single-site alloy catalysts using a degree-of-isolation descriptor

Geometrically isolated metal atoms in alloy catalysts can target efficient and selective catalysis. However, the geometric and electronic disturbance between the active atom and its neighbouring atoms, that is, diverse microenvironments, makes the active site ambiguous. Herein, we demonstrate a methodology to describe the microenvironment and determine the effectiveness of active sites in single-site alloys. A simple descriptor, degree-of-isolation, is proposed, considering both electronic regulation and geometric modulation within a PtM ensemble (M = transition metal). The catalytic performance of PtM single-site alloy is examined thoroughly using this descriptor for an industrially important reaction, propane dehydrogenation. The volcano-shaped isolation-selectivity plot reveals a Sabatier-type principle for designing selective single-site alloys. Specifically, for a single-site alloy with a high degree-of-isolation, alternation of the active centre has a great impact on tuning selectivity, validated by the outstanding consistency between experimental propylene selectivity and the computational descriptor.

Ethane Dehydrogenation over the Core-Shell Pt-Based Alloy Catalysts: Driven by Engineering the Shell Composition and Thickness

Pt-based catalysts as the commercial catalysts in ethane dehydrogenation (EDH) face one of the main challenges of realizing the balance between coke formation and catalytic activity. In this work, a strategy to drive the catalytic performance of EDH on Pt-Sn alloy catalysts is proposed by rationally engineering the shell surface structure and thickness of core-shell Pt@Pt₃Sn and Pt₃Sn@Pt catalysts from a theoretical perspective. Eight types of Pt@Pt₃Sn and Pt₃Sn@Pt catalysts with different Pt and Pt₃Sn shell thicknesses are considered and compared with the industrially used Pt and Pt₃Sn catalysts. Density functional theory (DFT) calculations completely describe the reaction network of EDH, including the side reactions of deep dehydrogenation and C-C bond cracking. Kinetic Monte Carlo (kMC) simulations reveal the influences of the catalyst surface structure, experimentally related temperatures, and reactant partial pressures. The results show that CHCH* is the main precursor for coke formation, and Pt@Pt₃Sn catalysts generally have higher C₂H₄(g) activity and lower selectivity compared to those of Pt₃Sn@Pt catalysts, which is attributed to the unique surface geometrical and electronic properties. 1Pt₃Sn@4Pt and 1Pt@4Pt₃Sn are screened out as catalysts exhibiting excellent performance; especially, the 1Pt₃Sn@4Pt catalyst has much higher C₂H₄(g) activity and 100% C₂H₄(g) selectivity compared to those of 1Pt@4Pt₃Sn and the widely used Pt and Pt₃Sn catalysts. The two descriptors C₂H₅* adsorption energy and reaction energy of its dehydrogenation to C₂H₄* are proposed to qualitatively evaluate the C₂H₄(g) selectivity and activity, respectively. This work facilitates a valuable exploration for optimizing the catalytic performance of core-shell Pt-based catalysts in EDH and reveals the great importance of the fine control of the catalyst shell surface structure and thickness.

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.

Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, and nanoparticles in the framework and framework-associated sites and extra-framework positions, thus affording the metal-in-zeolite catalysts outstanding activity, unique shape selectivity, and enhanced stability and recyclability in the processes of Brønsted acid-, Lewis acid-, and extra-framework metal-catalyzed reactions. Especially, thanks to the advances in zeolite synthesis and characterization techniques in recent years, zeolite-confined extra-framework metal catalysts (denoted as metal@zeolite composites) have experienced rapid development in heterogeneous catalysis, owing to the combination of the merits of both active metal sites and zeolite intrinsic properties. In this review, we will present the recent developments of synthesis strategies for incorporating and tailoring of active metal sites in zeolites and advanced characterization techniques for identification of the location, distribution, and coordination environment of metal species in zeolites. Furthermore, the catalytic applications of metal-in-zeolite catalysts are demonstrated, with an emphasis on the metal@zeolite composites in hydrogenation, dehydrogenation, and oxidation reactions. Finally, we point out the current challenges and future perspectives on precise synthesis, atomic level identification, and practical application of the metal-in-zeolite catalyst system.

A Robust and Efficient Propane Dehydrogenation Catalyst from Unexpectedly Segregated Pt2Mn Nanoparticles

The increasing demand for short chain olefins like propene for plastics production and the availability of shale gas make the development of highly performing propane dehydrogenation (PDH) catalysts, robust toward industrially applied harsh regeneration conditions, a highly important field of research. A combination of surface organometallic chemistry and thermolytic molecular precursor approach was used to prepare a nanometric, bimetallic Pt-Mn material (3 wt % Pt, 1.3 wt % Mn) supported on silica via consecutive grafting of a Mn and Pt precursor on surface OH groups present on the support surface, followed by a treatment under a H₂ flow at high temperature. The material exhibits a 70% fraction of the overall Mn as Mn^II single sites on the support surface; the remaining Mn is incorporated in segregated Pt₂Mn nanoparticles. The material shows great performance in PDH reaction with a low deactivation rate. In particular, it shows outstanding robustness during repeated regeneration cycles, with conversion and selectivity stabilizing at ca. 37 and 98%, respectively. Notably, a material with a lower Pt loading of only 0.05 wt % shows an outstanding catalytic performance─initial productivity of 4523 g_C3H6/g_Pt h and an extremely low k_d of 0.003 h^-1 under a partial pressure of H₂, which are among the highest reported productivities. A combined in situ X-ray absorption spectroscopy, scanning transmission electron microscopy, electron paramagnetic resonance, and metadynamics at the density functional theory level study could show that the strong interaction between the Mn^II-decorated support and the unexpectedly segregated Pt₂Mn particles is most likely responsible for the outstanding performance of the investigated materials.

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.

Propane Dehydrogenation over PtSn/Al2O3 Catalysts: Influence of Urea to Al(NO3)3·9H2O Ratio

Al2O3 supports were synthesized by the hydrothermal method and PtSn/Al2O3 catalysts were prepared by incipient-wetness impregnation method. The influence of the ratio of urea to Al(NO3)3·9H2O on the structure and catalytic performance for propane dehydrogenation was investigated. The catalysts were characterized by XRD, N2 adsorption–desorption, SEM, H2-TPR, NH3-TPD and Raman. The results show that the ratios of urea to Al(NO3)3·9H2O influence the morphology and phy-chemical properties of Al2O3 support, which influence the dispersion of PtSn active sites and the interaction of Pt and Sn on PtSn/Al2O3 catalysts. The PtSn/Al2O3-9 catalyst possesses the highest interaction of Pt and Sn, which result in high dispersion of active sites. The PtSn/Al2O3-9 catalyst shows high propane conversion and low deactivation rate among these catalysts.

Propane Dehydrogenation Catalyzed by Isolated Pt Atoms in ≡SiOZn-OH Nests in Dealuminated Zeolite Beta

Atomically dispersed noble metal catalysts have drawn wide attention as candidates to replace supported metal clusters and metal nanoparticles. Atomic dispersion can offer unique chemical properties as well as maximum utilization of the expensive metals. Addition of a second metal has been found to help reduce the size of Pt ensembles in bimetallic clusters; however, the stabilization of isolated Pt atoms in small nests of nonprecious metal atoms remains challenging. We now report a novel strategy for the design, synthesis, and characterization of a zeolite-supported propane dehydrogenation catalyst that incorporates predominantly isolated Pt atoms stably bonded within nests of Zn atoms located within the nanoscale pores of dealuminated zeolite Beta. The catalyst is stable in long-term operation and exhibits high activity and high selectivity to propene. Atomic resolution images, bolstered by X-ray absorption spectra, demonstrate predominantly atomic dispersion of the Pt in the nests and, with complementary infrared and nuclear magnetic resonance spectra, determine a structural model of the nested Pt.

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.

Doubly Decorated Platinum-Gallium Intermetallics as Stable Catalysts for Propane Dehydrogenation

Propane dehydrogenation (PDH) is a promising chemical process that can satisfy the increasing global demand for propylene. However, the Pt-based catalysts that have been reported thus far are typically deactivated at ≥600 °C by side reactions and coke formation. Thus, such catalysts possess an insufficient life. Herein, we report a novel catalyst design concept, namely, the double decoration of PtGa intermetallics by Pb and Ca, which synergize the geometric and electronic promotion effects on the catalyst stability, respectively. Pb is deposited on the three-fold Pt₃ sites of the PtGa nanoparticles to block them, whereas Ca, which affords an electron-enriched single-atom-like Pt₁ site, is placed around the nanoparticles. Thus, PtGa-Ca-Pb/SiO₂ exhibits an outstandingly high catalytic stability, even at 600 °C (k_d =0.00033 h^-1 , τ=3067 h), and almost no deactivation of the catalyst was observed for up to 1 month for the first time.

Spatially isolated cobalt oxide sites derived from MOFs for direct propane dehydrogenation

The "active site isolation" strategy has been proved to be efficient for enhancing the catalytic performance in propane dehydrogenation (PDH). Herein, spatially isolated cobalt oxide sites within nitrogen-doped carbon (NC) layers supported on silicalite-1 zeolite (CoO_x@NC/S-1) were synthesized by a two-step process consisting of the pyrolysis of bimetallic Zn/Co zeolitic imidazole frameworks loaded on silicalite-1 (ZnCo-ZIF/S-1) under N₂ and the subsequent calcination in air atmosphere. This catalyst possesses exceptional catalytic performance for PDH with the propane conversion of 40% and the propene selectivity of >97%, and no apparent deactivation is observed after 10 h PDH reaction at 600 °C. With intensive characterizations and experiments, it is indicated that the real active sites of CoO_x@NC/S-1 are isolated CoO sites during the PDH process. In situ FT-IR spectroscopy shows the same intermediate product (Co-C₃H₇) during both propane dehydrogenation and propene hydrogenation, indicating that they have a reverse reaction process, and a reaction mechanism for PDH is proposed accordingly.

Subsurface-Regulated PtGa Nanoparticles Confined in Silicalite-1 for Propane Dehydrogenation

Propane dehydrogenation (PDH) is one of the most promising techniques to produce propylene. Industrial Pt-based catalysts often suffer from short-time stability under high temperature due to serious sintering and coke deposition via undesired side reactions. Detailed reaction mechanism on the surface of Pt-based nanoparticle has been well studied, while the subsurface effect remains mostly unstudied. Herein, supported PtGa nanoparticles with different surface and subsurface composition was evidenced by extended X-ray absorption fine structure (EAXFS) spectra and energy dispersive X-ray spectroscopy (EDS). Theoretical simulation demonstrated subsurface regulation would increase the electron density of surface Pt and thus weaken propylene adsorption. Propylene selectivity on the PtGa-subsurface nanoparticles was up to 98% at 600 °C while that on the Pt-subsurface nanoparticles was only 95%. Furthermore, rational designed PtGa alloy nanoparticles were encapsulated in MFI zeolite to inhibit sintering and coke deposition for enhanced catalytic stability.

Template-Directed Rapid Synthesis of Pd-Based Ultrathin Porous Intermetallic Nanosheets for Efficient Oxygen Reduction

Atomically ordered intermetallic nanoparticles exhibit improved catalytic activity and durability relative to random alloy counterparts. However, conventional methods with time-consuming and high-temperature syntheses only have rudimentary capability in controlling the structure of intermetallic nanoparticles, hindering advances of intermetallic nanocatalysts. We report a template-directed strategy for rapid synthesis of Pd-based (PdM, M=Pb, Sn and Cd) ultrathin porous intermetallic nanosheets (UPINs) with tunable sizes. This strategy uses preformed seeds, which act as the template to control the deposition of foreign atoms and the subsequent interatomic diffusion. Using the oxygen reduction reaction (ORR) as a model reaction, the as-synthesized Pd₃ Pb UPINs exhibit superior activity, durability, and methanol tolerance. The favored geometrical structure and interatomic interaction between Pd and Pb in Pd₃ Pb UPINs are concluded to account for the enhanced ORR performance.

Enhanced performances of bimetallic Ga-Pt nanoclusters confined within silicalite-1 zeolite in propane dehydrogenation

Ga-based catalysts are promising for use in propane dehydrogenation (PDH) because of the relatively superior activity, but the conventional Ga-based catalysts usually suffer from serious deactivation and unsatisfactory propene selectivity. Here, ultrafine bimetallic Ga-Pt nanocatalysts encapsulated into silicalite-1 (S-1) zeolites (GaPt@S-1) were synthesized by a facile ligand-protected direct H₂-reduction method. It is indicated that this catalyst is composed of confined ultra-small GaPt alloy nanoclusters and a part of isolated tetrahedral coordination of Ga species. The confined GaPt alloy nanoclusters are the active sites for PDH reaction, and their high electron density could boost the desorption of products, resulting in a high propene selectivity of 92.1% and propene formation rate of 20.5 mol g^-1_Pt h^-1 at 600 °C. Moreover, no obvious deactivation was observed over GaPt@S-1 catalyst even after 24 h on stream at 600 °C, affording an extremely low deactivation constant of 0.0068 h^-1, which is much lower than that of the conventional Ga-based catalysts. Notably, the restriction of the zeolite can enhance the regeneration stability of the catalyst, and the catalytic activity kept unchanged after four consecutive cycles.

Metal-based catalysts for the non-oxidative dehydrogenation of light alkanes to light olefins

This review provides an overview of metal-based catalysts, including Pt-, Pd-, Rh- and Ni-based bimetallic catalysts for non-oxidative dehydrogenation of light alkanes to olefins.