Impregnating Subnanometer Metallic Nanocatalysts into Self-Pillared Zeolite Nanosheets

Efficient Generation of Negative Hydrogen with Bimetallic-Ternary-Structured Catalysts for Nitrobenzene Hydrogenation

Transition metal-catalyzed transfer hydrogenation (TH) with in situ negative hydrogen (H-) has received extensive attention as an alternative to conventional high-pressure hydrogenation processes. However, the insufficient activity of hydrogen production and unclear the conversion process of hydrogenation remain a great challenge. In this work, brand new bimetallic ternary-structured catalysts (Ru1+nM1-TiO2, M=Co, Cu, Fe, Ni) were synthesized to efficiently generate H- donors from ammonia borane (AB, NH3BH3) for nitrobenzene hydrogenation under moderate conditions. The Ru1+nCo1-TiO2 catalysts exhibited highest activity for hydrogen production form AB hydrolysis with a TOF value of 2716 min-1. The Ru1+nCo1-TiO2 achieved >90 % yields within 3-4 hours in converting nitrobenzene to anilines using AB. Mechanistic studies revealed that the high hydrolysis activity was due to that the Ru SA and Co SA sites of the bimetallic-ternary-structured catalyst required the lowest energy for the activation of AB and H2O, respectively. Remarkably, the Co SA and Ru clusters exhibited an obvious synergistic effect in the TH process, which promoted the tandem hydrogenation of nitroaromatics. This work demonstrated an efficient approach to generate H- donor with bimetallic-ternary-structured catalysts in TH process and further provided new inspiration on the development of multifunctional catalysts.

Integration of Ultrasmall Pt Clusters With Silanol Groups in Pure Silica Zeolites for Robust Formaldehyde Oxidation

Formaldehyde (HCHO) is a major indoor air pollutant that poses serious health risks. Catalytic oxidation of HCHO to CO2 and H2O at room temperature offers an efficient solution. Supported Pt nanoparticles are the most efficient catalysts, but challenges such as high cost and water resistant, limit their widespread application. Herein, we employ a ligand-protected direct hydrogen reduction strategy to encapsulate ultrafine Pt clusters within hydrophobic silicalite-1 zeolite. Cs-corrected scanning transmission electron microscopy, x-ray absorption, and solid nuclear magnetic resonance measurements confirmed that the Pt clusters are stabilized within zeolite channels by adjacent silanol groups. The optimized Pt@S-1-400H catalyst achieved complete HCHO removal at room temperature, with even low Pt loading of 0.1 wt%, affording a high specific activity of 171.9 molHCHO·molPt -1·h-1, representing the top level among all state-of-the-art Pt-based catalysts. Significantly, the hydrophobic nature of silicalite-1 ensures excellent water resistance and long-term stability for the Pt@S-1-400H catalyst. In situ infrared spectroscopy reveals that silanol sites facilitate HCHO adsorption and the formation of formate intermediates. The synergistic effect between Pt clusters and adjacent silanol sites enhances the HCHO oxidation performance. The simple and cost-effective approach, combined with its excellent activity and stability, holds significant potential for effectively eliminating indoor pollutants in practical applications.

Data-driven discovery of Pt single atom embedded germanosilicate MFI zeolite catalysts for propane dehydrogenation

Zeolite-confined metal is an important class of heterogeneous catalysts, demonstrating exceptional catalytic performance in many reactions, but the identification of a stable metal-zeolite combination with a simple synthetic method remains a top challenge. Here artificial intelligence methods, particularly global neural network potential based large-scale atomic simulation, are utilized to design Pt-containing zeolite frameworks for propane-to-propene conversion. We show that out of the zeolite database (>220 structure framework) and more than 100,000 Pt/Ge differently distributed configurations, there are only three Ge-containing zeolites, germanosilicate (MFI, IWW and SAO) that are predicted to be capable of stabilizing Pt single atom embedded in zeolite skeleton and at the meantime allowing propane fast diffusion. Among, the Pt1@Ge-MFI catalyst is successfully synthesized via a simple one-pot synthesis without a lengthy post-treatment procedure, and characterized by high-resolution experimental techniques. We demonstrate that the catalyst features an in-situ formed [GePtO3H2] active site under the reductive reaction condition that can achieve long-term (>750 h) high activity and selectivity (98%) for propane dehydrogenation. Our simple catalyst synthesis holds promise for scale-up industrial applications that can now be rooted in first principles via data-driven catalyst design.

Anion modulation enhances the internal electric field of CuCo2O4 to improve the catalysis in ammonia borane hydrolysis

Ammonia borane (NH3BH3, AB) is considered a promising chemical hydrogen storage material. The development of efficient, stable, and economical catalysts for AB hydrolysis is essential for realizing the hydrogen energy economy. In this study, a series of p-p heterojunction catalysts, labeled M (P/S/Cl)-CuCo2O4, were fabricated using the high-temperature vapor phase method to achieve anionic interface gradient doping. Due to the differences in electronegativity among the anions P/S/Cl-O, electron-rich and electron-deficient regions are generated at the interface, inducing the formation of local p-p heterojunctions with built-in electric fields (BIEF). The difference in work function (ΔWf) at the interface enhances the strength of the BIEF. Because of the positive influence of the BIEF on the adsorption of intermediates and interfacial behavior, the catalytic performance of P-CuCo2O4, characterized by a hydrogen evolution rate (HER) of 1125 mLH2(gcat·min)-1, is significantly higher than that of intrinsic CuCo2O4, which has an HER of 705 mLH2(gcat·min)-1. Its apparent activation energy of only 32.25 kJ/mol is superior to that of previous non-precious metal catalysts. Density functional theory (DFT) further confirms that the construction and enhancement of the BIEF can reduce the band gap, accelerate electron transfer, regulate the metal d-band center, and enhance the adsorption of AB and H2O molecules. This process facilitates the elongation and breakage of the O-H bond length in H2O and the B-H bond length in AB, thereby promoting the release of H2.

Design and engineering of microenvironments of supported catalysts toward more efficient chemical synthesis

Catalytic species such as molecular catalysts and metal catalysts are commonly attached to varieties of supports to simplify their separation and recovery and accommodate various reaction conditions. The physicochemical microenvironments surrounding catalytic species play an important role in catalytic performance, and the rational design and engineering of microenvironments can achieve more efficient chemical synthesis, leading to greener and more sustainable catalysis. In this review, we highlight recent works addressing the topic of the design and engineering of microenvironments of supported catalysts, including supported molecular catalysts and supported metal catalysts. Six types of materials, including oxide nano/microparticle, mesoporous silica nanoparticle (MSN), polymer nanomaterial, reticular material, zeolite, and carbon-based nanomaterial, are widely used as supports for the immobilization of catalytic species. We summarize and discuss the synthesis and modification of supports and the positive effects of microenvironments on catalytic properties such as metal-support interaction, molecular recognition, pseudo-solvent effect, regulating mass transfer, steric effect, etc. These design principles and engineering strategies allow access to a better understanding of structure-property relationships and advance the development of more efficient catalytic processes.

Comparative Study of PtM (M=Cu, Zn, Ga, Mn, Fe, In, Ce) Bimetals on Zincosilicate for Propane Dehydrogenation Reaction

Silicoaluminate zeolites have relatively strong Brönsted (B) acid properties that can easily lead to deep cracking reactions, making them less favourable as carriers for propane dehydrogenation. Here, we utilise zincosilicate zeolite with less B-acid produced by the introduction of the heteroatom Zn into the framework as a carrier, followed by simultaneous ion exchange (IE) of M monometallic or PtM bimetallic (M=Cu, Zn and Ga, etc.). The optimized PtZn/Zn-4 exhibits a superior propane dehydrogenation performance over PtCu/Zn-4 and PtGa/Zn-4, which can achieve a propane conversion of about 30 % in a pure propane atmosphere at 550 °C and can be operated for at least 168 h without significant deactivation. Characterization techniques such as spherical aberration corrected transmission electron microscopy, in situ X-ray photoelectron spectroscopy, and in situ diffuse reflectance infrared fourier transform spectroscopy with different gas adsorptions are used to investigate these PtM@zeolite catalysts in order to deepen the understanding of acid site identification, promoter effect and catalysis.

Study of the zeolite-catalyzed isomerization of 1-methylnaphthalene

Isomerization of 1-methylnaphthalene (1-MN) to 2-methylnaphthalene (2-MN) is a crucial step in the production of 2,6-dimethylnaphthalene (2,6-DMN), which is an important raw material for polyethylene naphthalate (PEN). Herein, the isomerization of 1-MN was systemically investigated over beta zeolite. Firstly, reaction conditions were systemically optimized, by which enhanced catalytic performance was obtained. Thereafter, the effect of nitride on the catalytic performance was investigated using a series of characterization techniques and DFT calculations, revealing that firm adsorption of nitride on acid sites was the main reason for catalyst deactivation. Activity of the deactivated catalyst was difficult to recover via extraction with hot benzene. Fortunately, catalytic performance could be effectively recovered through coke-burning, wherein the framework and acid sites were well-preserved during calcination.

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 39911mo l H 2 mo l Pt - 1 mi n - 1 ${\mathrm{mo}}{{{\mathrm{l}}}_{{{{\mathrm{H}}}_{\mathrm{2}}}}}{\mathrm{\ mo}}{{{\mathrm{l}}}_{{\mathrm{Pt}}}}^{{\mathrm{ - 1}}}{\mathrm{\ mi}}{{{\mathrm{n}}}^{{\mathrm{ - 1}}}}$ and turnover number of 2926829mo l H 2 mo l Pt - 1 ${\mathrm{mo}}{{{\mathrm{l}}}_{{{{\mathrm{H}}}_{\mathrm{2}}}}}{\mathrm{\ mo}}{{{\mathrm{l}}}_{{\mathrm{Pt}}}}^{{\mathrm{ - 1}}}$ 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 54878mo l H 2 mo l Pt - 1 mi n - 1 ${\mathrm{mo}}{{{\mathrm{l}}}_{{{{\mathrm{H}}}_{\mathrm{2}}}}}{\mathrm{\ mo}}{{{\mathrm{l}}}_{{\mathrm{Pt}}}}^{{\mathrm{ - 1}}}{\mathrm{\ mi}}{{{\mathrm{n}}}^{{\mathrm{ - 1}}}}$ 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.

Synthesis of self-pillared pentasil zeolites without organic templates and seeds

Self-pillared pentasil (SPP) zeolites have received considerable interest due to their distinctive intergrowth structure, while the precise process and mechanism for the formation of SPP zeolites remain obscure. Herein, SPP zeolites (ZSM-5) have been successfully synthesized by pre-aging an Al-rich gel without employing any organic templates or seeds for the first time. The as-synthesized SPP zeolites possess a notably high external surface area while the micropores for Ar adsorption are partially blocked by excess Na+, which can be fully recovered by Mg2+ or H+ exchange. The crystallization process is monitored and the impacts of synthesis parameters are investigated. The results show that self-pillaring originates from the partial lattice distortion at the intersections of nanosheets, offering a new insight into the self-pillaring process. Typically, with decreasing SiO2/Al2O3 ratio, more crossovers could be observed in the crystals, hinting that self-pillaring predominately occurs at the (101) plane of twins in the ZSM-5 precursor due to Al-rich lattice distortion. Finally, in the catalytic cracking of n-heptane, H-SPP zeolites exhibit superior performance to commercial H-ZSM-5 zeolites due to their abundant Brønsted acid sites arising from a low framework SiO2/Al2O3 ratio of ∼21 and the short diffusion path originating from the house-of-cards structure.

Preparation of Metal-Supported Nanostructured Zeolite Catalysts and their Applications in the Upgrading of Biomass-Derived Furans: Advances and Prospects

The development of platform chemicals derived from biomass, in particular, 5-hydroxymethylfurfural (5-HMF) and furfural (FUR), is of crucial importance in biorefinery. Over the past decades, metal-supported nanostructured zeolites, in particular, metal-supported hierarchically porous zeolites or metal-encapsulated zeolites, have been extensively elaborated because of their multiple functionalities and superior properties, for example, shape-selectivity, (hydro)thermal stability, tunable acidity and basicity, redox properties, improved diffusion, and intimacy of multiple active sites. In this review, the effects of such properties of metal-supported nanostructured zeolites on the enhanced catalytic performances in furanic compound upgrading are discussed. In addition, the recent rational design of metal-supported nanostructured zeolites is exemplified. Consequently, the ongoing challenges for further developing metal-supported nanostructured zeolites-based catalysts and their applications in HMF and FUR upgrading are identified.

Highly Dispersed Pd-CeOx Nanoparticles in Zeolite Nanosheets for Efficient CO2-Mediated Hydrogen Storage and Release

Formic acid (FA) dehydrogenation and CO2 hydrogenation to FA/formate represent promising methodologies for the efficient and clean storage and release of hydrogen, forming a CO2-neutral energy cycle. Here, we report the synthesis of highly dispersed and stable bimetallic Pd-based nanoparticles, immobilized on self-pillared silicalite-1 (SP-S-1) zeolite nanosheets using an incipient wetness co-impregnation technique. Owing to the highly accessible active sites, effective mass transfer, exceptional hydrophilicity, and the synergistic effect of the bimetallic species, the optimized PdCe0.2/SP-S-1 catalyst demonstrated unparalleled catalytic performance in both FA dehydrogenation and CO2 hydrogenation to formate. Remarkably, it achieved a hydrogen generation rate of 5974 molH2 molPd -1 h-1 and a formate production rate of 536 molformate molPd -1 h-1 at 50 °C, surpassing most previously reported heterogeneous catalysts under similar conditions. Density functional theory calculations reveal that the interfacial effect between Pd and cerium oxide clusters substantially reduces the activation barriers for both reactions, thereby increasing the catalytic performance. Our research not only showcases a compelling application of zeolite nanosheet-supported bimetallic nanocatalysts in CO2-mediated hydrogen storage and release but also contributes valuable insights towards the development of safe, efficient, and sustainable hydrogen technologies.

Probing Basal and Prismatic Planes of Graphitic Materials for Metal Single Atom and Subnanometer Cluster Stabilization

Supported metal single atom catalysis is a dynamic research area in catalysis science combining the advantages of homogeneous and heterogeneous catalysis. Understanding the interactions between metal single atoms and the support constitutes a challenge facing the development of such catalysts, since these interactions are essential in optimizing the catalytic performance. For conventional carbon supports, two types of surfaces can contribute to single atom stabilization: the basal planes and the prismatic surface; both of which can be decorated by defects and surface oxygen groups. To date, most studies on carbon-supported single atom catalysts focused on nitrogen-doped carbons, which, unlike classic carbon materials, have a fairly well-defined chemical environment. Herein we report the synthesis, characterization and modeling of rhodium single atom catalysts supported on carbon materials presenting distinct concentrations of surface oxygen groups and basal/prismatic surface area. The influence of these parameters on the speciation of the Rh species, their coordination and ultimately on their catalytic performance in hydrogenation and hydroformylation reactions is analyzed. The results obtained show that catalysis itself is an interesting tool for the fine characterization of these materials, for which the detection of small quantities of metal clusters remains a challenge, even when combining several cutting-edge analytical methods.

Silanol-Stabilized Atomically Dispersed Ptδ+-Ox-Sn Active Sites in Protozeolite for Propane Dehydrogenation

Crystalline zeolites have been proven to be excellent supports for confining subnanometric metal catalysts to boost the propane dehydrogenation (PDH) reaction. However, the introduced metallic species may suffer from severe sintering and limited stability during the catalytic process, especially when utilizing an industrial impregnation method for metal incorporation. In this study, we developed a new type of support based on amorphous protozeolite (PZ), taking advantage of its adjustable silanol chemistry and zeolitic microporous characteristic for stabilizing atomically dispersed PtSn catalyst via a simple, cost-effective coimpregnation process. The combination of X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy under CO atmosphere, and density functional theory calculations confirmed the formation of highly dispersed active Ptδ+-Ox-Sn species in PtSn/PZ. The PtSn/PZ catalyst exhibited a high propane conversion of 45.4% and a high propylene selectivity of 99% (WHSV= 3.6 h-1, 550 °C), with a high apparent rate coefficient of 565 molC3H6·gPt-1·h-1·bar-1 at a high WHSV of 108 h-1, presenting a top-level performance among the state-of-the-art Pt-based catalysts prepared by in situ synthesis and impregnation methods. The silanol density determined the chemical state of PtSn species, showing a change from atomically dispersed Ptδ+-Ox-Sn sites to PtSn alloy with decreasing silanol density of supports. This work provides a general strategy using silanol-rich amorphous protozeolite as support for stabilizing various metal catalysts by the simple impregnation method and also offers an effective way for fine tailoring the chemical state of metallic species via a silanol-engineered approach.

Two-dimensional molybdenum boride coordinating with ruthenium nanoparticles to boost hydrogen generation from hydrolytic dehydrogenation of ammonia borane

The coordination between carrier and active metal is critical to the catalytic efficiency of ammonia borane (AB) hydrolysis reaction. In the present study, we report a new type of catalytic support based on molybdenum boride (MBene) MoAl1-xB and demonstrate that the effective combination of MoAl1-xB with Ru nanoparticles can realize the significantly enhanced performance for hydrogen generation. Owing to the efficient activation and dissociation of reactants, the optimal Ru/MoAl1-xB catalyst achieves the large turnover frequency of 494 molH2 molRu-1 min-1, high hydrogen generation rate of 119817 mL min-1 gRu-1 and favorable apparent activation energy of 39.2 kJ mol-1 for the catalytic hydrolysis of AB under alkaline-free condition. The isotopic test suggests the cleavage of OH bond in H2O is the rate-determining step for hydrolysis reaction, while the fracture of B-H bond in AB is also well revealed by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy. Significantly, the flexible on-demand hydrogen generation is achieved by using chemical switches for on-off AB hydrolysis. This study provides a new support platform based on two-dimensional MBene to exploit efficient catalysts to boost AB dehydrogenation.

Regulating Second-Shell Coordination in Cobalt Single-Atom Catalysts toward Highly Selective Hydrogenation

Manipulating the local coordination environment of central metal atoms in single-atom catalysts (SACs) is a powerful strategy to exploit efficient SACs with optimal electronic structures for various applications. Herein, Co-SACs featured by Co single atoms with coordinating S atoms in the second shell dispersed in a nitrogen-doped carbon matrix have been developed toward the selective hydrogenation of halo-nitrobenzene. The location of the S atom in the model Co-SAC is verified through synchrotron-based X-ray absorption spectroscopy and theoretical calculations. The resultant Co-SACs containing second-coordination shell S atoms demonstrate excellent activity and outstanding durability for selective hydrogenation, superior to most precious metal-based catalysts. In situ characterizations and theoretical results verify that high activity and selectivity are attributed to the advantageous formation of the Co-O bond between p-chloronitrobenzene and Co atom at Co1N4-S moieties and the lower free energy and energy barriers of the reaction. Our findings unveil the correlation between the performance and second-shell coordination atom of SACs.

Zeolite-Templated Carbons Supported Rh and Ru Electrocatalysts for Highly Active Hydrogen Evolution Reaction

Here, we report the systematical synthesis of zeolite-templated carbon (ZTC) supported Ru and Rh mono- or bi-metallic electrocatalysts towards hydrogen evolution reaction (HER). The zeolite A or ZSM-5 derived ZTC supports and metal sites were adjusted, and all electrocatalysts outperformed the commercial Pt/C electrocatalyst for HER performance. In particular, the RhRu/(ZTC/ZSM5) sample exhibited superior catalytic performance with the overpotential of 24.8 mV@10 mA ⋅ cm-2, and outstanding stability with 1 mV drop after 20000 cyclic voltammetry circles. This work offers a simple impregnation method for the synthesis of highly performed HER electrocatalysts supported on porous zeolite-templated carbon.

Double Unit-Cell Silicogermanate Nanosheets Developed by Salting-Out Mechanism for Biomass Conversion

Zeolite nanosheets with an extremely thin thickness featuring both unique pore systems and low diffusion resistance have the potential to achieve enhanced catalytic performance in the conversion of bulky molecular biomass. The preparation of unit-cell level nanosheets generally requires complex and costly multifunctional surfactants or an organic structure-directing agent (OSDA). Commercially available and environmentally friendly ionic liquids can also direct the structure of zeolite nanosheets by π-π stacking when these kinds of OSDA are used in large amount. Herein, we first report unit-cell-sized silicogermanate nanosheets of NS-IM-20 (UWY topology), 5 nm in thickness, which were synthesized at a relatively low ionic liquid concentration with the assistance of halide ion (Cl-). The Pd-loaded NS-IM-20 nanosheets with a hierarchical porosity and moderate acidity act as promising bifunctional catalysts for selective biomass conversion.

Unraveling the Synergistic Mechanism of Ir Species with Various Electron Densities over an Ir/ZSM-5 Catalyst Enables High-Efficiency NO Reduction by CO

Selective catalytic reduction using CO as a reducing agent (CO-SCR) has exhibited its application potential in coal-fired, steel, and other industrial sectors. In comparison to NH3-SCR, CO-SCR can achieve synergistic control of CO and NO pollutants, making it a powerful denitrification technology that treats waste with waste. Unfortunately, the competitive adsorption of O2 and NO on CO-SCR catalysts inhibits efficient conversion of NOx under O2-containing conditions. In this work, we obtained two Ir sites with different electron densities, Ir1 single atoms in the oxidized Irδ+ state and Ir0 nanoparticles in the metallic state, by controlled pretreatment of the Ir/ZSM-5 catalyst with H2 at 200 °C. The coexistence of Ir1 single atoms and Ir0 nanoparticles on ZSM-5 creates a synergistic effect, which facilitates the reduction of NO through CO in the presence of O2, following the Langmuir-Hinshelwood mechanism. The ONNO dimer is formed on the Ir1 single atom sites and then spills over to the neighboring Ir0 nanoparticles for subsequent reduction to N2 by CO. Specifically, this tandem reaction enables 83% NO conversion and 100% CO conversion on an Ir-based catalyst at 250 °C under 3% O2.

Dual catalytic activity of a cucurbit[7]uril-functionalized metal alloy nanocomposite for sustained hydrogen generation: hydrolysis of ammonia borane and electrocatalysts for the hydrogen evolution reaction

H2 is one of the most attractive fuel alternatives to the existing fossil fuels that cause detrimental environmental issues. Thus, there has been an upsurge in the research on the production of green hydrogen. In this view, cucurbit[7]uril (CB7)-functionalized Co:Ni alloy nanocomposites with different compositions, reported here for the first time, were synthesized to synergise the catalytic activities of a nanoalloy and CB7 and screened for hydrogen generation via hydrolysis of ammonia borane (AB). The (Co85:Ni15)50:(CB7)50 nanocomposite exhibited enhanced catalytic performance for AB hydrolysis even at room temperature as compared to the nanoalloy without CB7. Efficient release of ammonia-free green H2 is ensured by the retention of NH3 by the surface functionalized CB7 macrocycles. For sustained release, a novel and cost-effective procedure was used to regenerate AB from the by-product, and the H2 release activity was verified to be on par with commercial AB. The used nanocomposite magnetically separated from the by-product solution was shown to be an efficient electrochemical catalyst for the hydrogen evolution reaction (HER). The cucurbit[7]uril-functionalized Co:Ni nanocomposite demonstrates remarkable dual catalytic performance to generate clean hydrogen from both the hydrolysis of AB at room temperature and the electrochemical HER, thus opening new avenues in supramolecular chemistry for developing noble metal-free catalysts with high activity and long-term stability.

Insights into the hydrogen generation and catalytic mechanism on Co-based nanocomposites derived from pyrolysis of organic metal precursor

Hydrogen generation from boron hydride is important for the development of hydrogen economy. Cobalt (Co) element has been widely used in the hydrolysis of boron hydride. Pyrolysis is a common method for materials synthesis in catalytic fields. Herein, Co-based nanocomposites derived from the pyrolysis of organic metal precursors and used for hydrolysis of boron hydride are summarized and discussed. The different precursors consisting of MOF, supported, metal, and metal phosphide precursors are summarized. The catalytic mechanism consisting of dissociation mechanism based on oxidative addition-reduction elimination, pre-activation mechanism, SN2 mechanism, four-membered ring mechanism, and acid-base mechanism is intensively discussed. Finally, conclusions and outlooks are conveyed from the design of high-efficiency catalysts, the characterization of catalyst structure, the enhancement of catalytic activities, the investigation of the catalytic mechanism, and the catalytic stability of active structure. This review can provide guidance for designing high-efficiency catalysts and boosting development of hydrogen economy.

Co-Cu nanoparticles uniformly embedded in the intra-crystalline mesoporous Silicalite-1 for catalytic ammonia borane hydrolysis

Zeolite-encaged metal nanoparticles (NPs) catalysts are emerging as a new frontier owing to their superior ability to stabilize the structure and catalytic performance in the thermal and environmental catalytic reaction. However, the pore size below 2 nm of the conventional zeolites usually limits the accessibility of metal active sites. Herein, Co-Cu NPs of about 2.5-3.5 nm were uniformly encapsulated in the intracrystalline mesoporous Silicalite-1 (S-1) through alkali-treatment ligand-assisted strategy. The obtained sample (termed CoxCu1-x@HS-1) exhibited efficient activity and stability in the ammonia borane hydrolysis with the highest TOF value of 21.46 molH2·molMe-1·min-1. UV-vis DRS spectra indicated that intracrystalline mesopores have greatly improved the openness and accessibility of the active sites, thus improving their catalytic performance. The introduction of Cu regulates the electronic properties of Co, further increasing hydrogen production activity. This research creates new prospects to design other high-performance hierarchical porous zeolite-confined metal/metal oxide catalysts.

Strengthening the Metal-Acid Interactions by Using CeO2 as Regulators of Precisely Placing Pt Species in ZSM-5 for Furfural Hydrogenation

Understanding the synergism between the metal site and acid site is of great significance in boosting the efficiency of bi-functional catalysts in many heterogeneous reactions, particularly in biomass upgrading. Herein, a "confined auto-redox" strategy is reported to fix CeO2-anchored Pt atoms on the inner wall of a ZSM-5 cage, achieving the target of finely controlling the placements of the two active sites. Compared with the conventional surface-supported counterpart, the encapsulated Pt/CeO2@ZSM-5 catalyst possesses remarkably-improved activity and selectivity, which can convert >99% furfural into cyclopentanone with 97.2% selectivity in 6 h at 160 °C. Besides the excellent catalytic performance, the ordered metal-acid distribution also makes such kind of catalyst an ideal research subject for metal-acid interactions. The following mechanization investigation reveals that the enhancement is strongly related to the unique encapsulation structure, which promotes the migration of the reactants over different active sites, thereby contributing to the tandem reaction.

Advances in Synthesis and Applications of Single-Atom Catalysts for Metal Oxide-Based Gas Sensors

As a stable, low-cost, environment-friendly, and gas-sensitive material, semiconductor metal oxides have been widely used for gas sensing. In the past few years, single-atom catalysts (SACs) have gained increasing attention in the field of gas sensing with the advantages of maximized atomic utilization and unique electronic and chemical properties and have successfully been applied to enhance the detection sensitivity and selectivity of metal oxide gas sensors. However, the application of SACs in gas sensors is still in its infancy. Herein, we critically review the recent advances and current status of single-atom catalysts in metal oxide gas sensors, providing some suggestions for the development of this field. The synthesis methods and characterization techniques of SAC-modified metal oxides are summarized. The interactions between SACs and metal oxides are crucial for the stable loading of single-atom catalysts and for improving gas-sensitive performance. Then, the current application progress of various SACs (Au, Pt, Cu, Ni, etc.) in metal oxide gas sensors is introduced. Finally, the challenges and perspectives of SACs in metal oxide gas sensors are presented.

Engineering a hollow bowl-like porous carbon-confined Ru-MgO hetero-structured nanopair as a high-performance catalyst for ammonia borane hydrolysis

Exploration of high-performance catalysts holds great importance for on-demand H2 production from ammonia borane (AB) hydrolysis. In this work, a hollow bowl-like porous carbon-anchored Ru-MgO hetero-structured nano-pair with high-intensity interfaces is made, using a tailored design approach. Consequently, the optimized catalyst shows AB hydrolysis activity with a turnover frequency value of 784 min-1 in aqueous media and 1971 min-1 in alkaline solvent. Robust durability is also achieved, with slight deactivation after a ten-cycle test. Combined experimental and theoretical calculations validate the positive function of the interface between Ru and MgO for facilitating H transfer and boosting water activation, thus leading to improved AB hydrolysis performance. This study could be valuable in guiding the upgradation of Ru catalytic systems, to advance their practical applications.

Stable Interfacial Ruthenium Species for Highly Efficient Polyolefin Upcycling

The present polyolefin hydrogenolysis recycling cases acknowledge that zerovalent Ru exhibits high catalytic activity. A pivotal rationale behind this assertion lies in the propensity of the majority of Ru species to undergo reduction to zerovalent Ru within the hydrogenolysis milieu. Nonetheless, the suitability of zerovalent Ru as an optimal structural configuration for accommodating multiple elementary reactions remains ambiguous. Here, we have constructed stable Ru0-Ruδ+ complex species, even under reaction conditions, through surface ligand engineering of commercially available Ru/C catalysts. Our findings unequivocally demonstrate that surface-ligated Ru species can be stabilized in the form of a Ruδ+ state, which, in turn, engenders a perturbation of the σ bond electron distribution within the polyolefin carbon chain, ultimately boosting the rate-determining step of C-C scission. The optimized catalysts reach a solid conversion rate of 609 g·gRu-1·h-1 for polyethylene. This achievement represents a 4.18-fold enhancement relative to the pristine Ru/C catalyst while concurrently preserving a remarkable 94% selectivity toward valued liquid alkanes. Of utmost significance, this surface ligand engineering can be extended to the gentle mixing of catalysts in ligand solution at room temperature, thus rendering it amenable for swift integration into industrial processes involving polyolefin degradation.

Encapsulation of Palladium Carbide Subnanometric Species in Zeolite Boosts Highly Selective Semihydrogenation of Alkynes

The selective hydrogenation of alkynes to alkenes is a crucial step in the synthesis of fine chemicals. However, the widely utilized palladium (Pd)-based catalysts often suffer from poor selectivity. In this work, we demonstrate a carbonization-reduction method to create palladium carbide subnanometric species within pure silicate MFI zeolite. The carbon species can modify the electronic and steric characteristics of Pd species by forming the predominant Pd-C4 structure and, meanwhile, facilitate the desorption of alkenes by forming the Si-O-C structure with zeolite framework, as validated by the state-of-the-art characterizations and theoretical calculations. The developed catalyst shows superior performance in the selective hydrogenation of alkynes over mild conditions (298 K, 2 bar H2 ), with 99 % selectivity to styrene at a complete conversion of phenylacetylene. In contrast, the zeolite-encapsulated carbon-free Pd catalyst and the commercial Lindlar catalyst show only 15 % and 14 % selectivity to styrene, respectively, under identical reaction conditions. The zeolite-confined Pd-carbide subnanoclusters promise their superior properties in semihydrogenation of alkynes.

Mild Hydrogenation of 2-Furoic Acid by Pt Nanoparticles Dispersed in a Hierarchical ZSM-5 Zeolite

Hydrogenation of biobased compounds can add value to platform molecules obtained from biomass refining. Herein, we explore the hydrogenation of 2-furoic acid (2-furancarboxylic acid, FCA), a derivative of furfural, with H2 generated in situ by NaBH4 hydrolysis at ambient conditions. Nearly complete conversion of FCA was obtained with tetrahydrofuroic acid (THFA) and 5-hydroxyvaleric acid (5-HVA) as the only two reaction products over Pt nanoparticles supported on hierarchical ZSM-5. Small Pt nanoparticles (2 to 3 nm) were stabilized by ZSM-5 nanosheets. At an optimized Pt loading, the Pt nanoparticles can catalyze the hydrolysis of NaBH4 and the subsequent hydrogenation of FCA with the assistance of Brønsted acid sites. Nanostructuring ZSM-5 into nanosheets and its acidity contributes to the stability of the dispersed Pt nanoparticles. Deactivation due to NaBO2 deposition on the Pt particles can be countered by a simple washing treatment. Overall, this approach shows the promise of mild hydrogenation of biobased feedstock coupled with NaBH4 hydrolysis.

Dual Pd-Acid Sites Confined in a Hierarchical Core-Shell Structure for Hydrogenation of Nitrobenzene

A core-shell structured Pd@TS-1@meso-SiO2 catalyst with confined Pd nanometals has been fabricated by one-pot synthesis, impregnation method and sol-gel method. With the promotion of acid sites and protection of mesoporous silica shell, Pd@TS-1@meso-SiO2 shows higher activity than commercial comparison and higher stability than sample without mesoporous silica shell in the hydrogenation of nitrobenzene. The schematic illustration of the synergy effect is also proposed.

Mixed Plastics Wastes Upcycling with High-Stability Single-Atom Ru Catalyst

Mixed plastic waste treatment has long been a significant challenge due to complex composition and sorting costs. In this study, we have achieved a breakthrough in converting mixed plastic wastes into a single chemical product using our innovative single-atom catalysts for the first time. The single-atom Ru catalyst can convert ∼90% of real mixed plastic wastes into methane products (selectivity >99%). The unique electronic structure of Ru sites regulates the adsorption energy of mixed plastic intermediates, leading to rapid decomposition of mixed plastics and superior cycle stability compared to traditional nanocatalysts. The global warming potential of the entire process was evaluated. Our proposed carbon-reducing process utilizing single-atom catalysts launches a new era of mixed plastic waste valorization.

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

Fluorination of Covalent Organic Framework Reinforcing the Confinement of Pd Nanoclusters Enhances Hydrogen Peroxide Photosynthesis

Metal-isolated clusters (MICs) physically confined on photoactive materials are of great interest in the field of photosynthesis of hydrogen peroxide (H2O2). Despite recent important endeavors, weak confinement of MICs in the reported photocatalytic systems leads to their low catalytic activity and stability. Herein, we report a new strategy of fluorinated covalent organic frameworks (COFs) to strongly confine Pd ICs for greatly boosting the photocatalytic activity and stability of H2O2 photosynthesis. Both experimental and theoretical results reveal that strong electronegative fluorine can increase the metal-support interaction and optimize the d-band center of Pd ICs, thus significantly enhancing the stability and activity of photocatalytic H2O2. An optimal TAPT-TFPA COFs@Pd ICs photocatalyst delivers a stable H2O2 yield rate of 2143 μmol h-1 g-1. Most importantly, the as-made TAPT-TFPA COFs@Pd ICs exhibit high catalytic stability over 100 h, which is the best among the reported materials.

Synthesis of Azoxy Compounds: from Copper Compounds to Mesoporous Silica-Encaged Ultrasmall Copper Catalysts

Azoxy compounds have aroused extensive attention due to their unique biological activities, but the chemical synthesis of these compounds often suffers from limitations due to their requirement for stoichiometric oxidants, high costs, and restricted substrate range. Herein, a series of azoxy compounds were constructed via facile coupling reactions by using cost-effective N-methoxyformamide and nitroso compounds over Cu-based catalysts, affording high product yields with excellent tolerance of functional groups. Significantly, the mesoporous silica nanosphere-encapsulated ultrasmall Cu (Cu@MSN) catalyst was developed via a one-pot synthetic method and first used for the synthesis of azoxy compounds. As compared with copper salt catalysts, the Cu@MSN catalyst exhibited remarkably enhanced catalytic activity and superior recycling stability. Such a Cu@MSN catalyst overcame the inherent drawbacks of low activity, fast deactivation, and difficult recycling of traditional metal salt catalysts in organic reactions. This work provides a green and efficient method for the construction of azoxy compounds and also creates new prospects for the application of nanoporous materials confined metal catalysts in organic synthesis.

Construction of a Novel Cascade Electrolysis-Heterocatalysis System by Using Zeolite-Encaged Ultrasmall Palladium Catalysts for H2 O2 Generation

In situ generation of hydrogen peroxide (H₂ O₂ ) has attracted extensive attention, especially in water treatment. However, traditional anthraquinones can only produce high-concentration H₂ O₂ and its transportation and storage are not convenient and dangerous. Herein, an in situ and on-demand strategy to produce H₂ O₂ by using a cascade water electrolysis together with a heterocatalysis system is provided. Beginning with water, H_2, and O₂ can be generated via electrolysis and then react with each other to produce H₂ O₂ immediately on efficient zeolite-encaged ultrasmall Pd catalysts. Significantly, the H₂ O₂ generation rate in the optimized cascade system reaches up to 0.85 mol L^-1 h^-1 g_Pd ^-1 , overcoming most of the state-of-the-art catalysts in previous literature. The confinement effect of zeolites is not only beneficial to the formation of highly dispersed metal species, promoting the H₂ O₂ generation, but also inhibits the H₂ O₂ decomposition, enhancing the production yield of H₂ O₂ . In addition, the effect of electrolytes, sizes of Pd species, as well as zeolite acidity are also systematically studied. This work provides a new avenue for H₂ O₂ generation via a highly efficient cascade electrolysis-heterocatalysis system by using zeolite-supported metal catalysts. The high catalytic efficiency and green process for H₂ O₂ generation make it very promising for further practical applications.

Facile construction of robust Ru-Co3O4 Mott-Schottky catalyst enabling efficient dehydrogenation of ammonia borane for hydrogen generation

Developing efficient catalysts for the dehydrogenation of ammonia borane (AB) is important for the safe storage and controlled release of hydrogen, but it is a challenging task. In this study, we designed a robust Ru-Co₃O₄ catalyst using the Mott-Schottky effect to induce favorable charge rearrangement. The self-created electron-rich Co₃O₄ and electron-deficient Ru sites at heterointerfaces are indispensable for the activation of the B-H bond in NH₃BH₃ and the OH bond in H₂O, respectively. The synergistic electronic interaction between the electron-rich Co₃O₄ and electron-deficient Ru sites at the heterointerfaces resulted in an optimal Ru-Co₃O₄ heterostructure that exhibited outstanding catalytic activity for the hydrolysis of AB in the presence of NaOH. The heterostructure had an extremely high hydrogen generation rate (HGR) of 12238 mL min^-1 g_cat^-1 and an expected high turnover frequency (TOF) of 755 mol_H2 mol_Ru^-1 min^-1 at 298 K. The activation energy needed for the hydrolysis was low (36.65 kJ mol^-1). This study opens up a new avenue for the rational design of high-performance catalysts for AB dehydrogenation based on the Mott-Schottky effect.

Recent Advances and Perspectives on Supported Catalysts for Heterogeneous Hydrogen Production from Ammonia Borane

Ammonia borane (AB), a liquid hydrogen storage material, has attracted increasing attention for hydrogen utilization because of its high hydrogen content. However, the slow kinetics of AB hydrolysis and the indefinite catalytic mechanism remain significant problems for its large-scale practical application. Thus, the development of efficient AB hydrolysis catalysts and the determination of their catalytic mechanisms are significant and urgent. A summary of the preparation process and structural characteristics of various supported catalysts is presented in this paper, including graphite, metal-organic frameworks (MOFs), metal oxides, carbon nitride (CN), molybdenum carbide (MoC), carbon nanotubes (CNTs), boron nitride (h-BN), zeolites, carbon dots (CDs), and metal carbide and nitride (MXene). In addition, the relationship between the electronic structure and catalytic performance is discussed to ascertain the actual active sites in the catalytic process. The mechanism of AB hydrolysis catalysis is systematically discussed, and possible catalytic paths are summarized to provide theoretical considerations for the designing of efficient AB hydrolysis catalysts. Furthermore, three methods for stimulating AB from dehydrogenation by-products and the design of possible hydrogen product-regeneration systems are summarized. Finally, the remaining challenges and future research directions for the effective development of AB catalysts are discussed.

Ternary alloy (FeCoNi) nanoparticles supported on hollow porous carbon with defects for enhanced oxygen evolution reaction

Low-cost non-noble metal nanoparticles are promising electrocatalysts that can catalyze oxygen evolution reaction (OER). Various factors such as poor activity and stability hinder the practical applications of these materials. The electroactivity and durability of the electrocatalysts can be improved by optimizing the morphology and composition of the materials. Herein, we report the successful synthesis of hollow porous carbon (HPC) catalysts loaded with ternary alloy (FeCoNi) nanoparticles (HPC-FeCoNi) for efficient OER. HPC is firstly synthesized by a facile carbon deposition method using the hierarchical porous zeolite ZSM-5 as the hard template. Numerous defects are generated on the carbon shell during the removal of zeolite template. Subsequently, FeCoNi alloy nanoparticles are supported on HPC by a sequence of impregnation and H₂ reduction processes. The synergistic effect between carbon defects and FeCoNi alloy nanoparticles endows the catalyst with an excellent OER performance (low overpotential of 219 mV; Tafel slope of 60.1 mV dec^-1) in a solution of KOH (1 M). A stable potential is maintained during the continuous operation over 72 h. The designed HPC-FeCoNi presents a platform for the development of electrocatalysts that can be potentially applied for industrial OER.

Defect-Enriched Hollow Porous Carbon Nanocages Enable Highly Efficient Chlorine Evolution Reaction

Metal-free carbon-based catalysts are crucial for the electrocatalytic chlorine evolution reaction (CER) to reduce the usage of noble metals and industrial cost. However, the corresponding catalytic activity of high overpotential and low durability hinders their wide application. Here, a hollow porous carbon (HPC) nanocage with a controlled oxygen electronic state around designed carbon defects for CER activity is reported. Alkali etching can bring defects in zeolite with a hollow structure. In a hard template strategy, the type of carbon defects is directly related to etching degree of the zeolite template. More importantly, the oxygen atoms can be "borrowed" from the zeolite framework by the defective carbon. The electron density around unsaturated O atoms can be decreased on the minor defects in carbon compared with that on large defects which is favorable for the adsorption of Cl^- . Consequently, the as-synthesized HPC nanocages with minor defects show excellent electrocatalytic performance for CER with a low overpotential of 94 mV at current density of 10 mA cm^-2 with good stability, which is superior to the commercial precious metal catalyst of dimensionally stable anode (DSA), and the best in the reported carbon materials. The designed carbon materials provide an option for metal-free industrial catalysts with significant CER activities.

Boosting Propane Dehydrogenation by the Regioselective Distribution of Subnanometric CoO Clusters in MFI Zeolite Nanosheets

Direct dehydrogenation of propane (PDH) has already been implemented worldwide in industrial processes to produce value-added propylene. The discovery of earth-abundant and environmentally friendly metal with high activity in C-H cleavage is of great importance. Co species encapsulated within zeolite are highly efficient for catalyzing direct dehydrogenation. However, exploring a promising Co catalyst remains a nontrivial target. Direct control of the regioselective distribution of Co species in the zeolite framework through altering their crystal morphology gives opportunities to modify the metallic Lewis acidic features, thus providing an active and appealing catalyst. Herein, we achieved the regioselective localization of highly active subnanometric CoO clusters in straight channels of siliceous MFI zeolite nanosheets with controllable thickness and aspect ratio. The subnanometric CoO species were identified by different types of spectroscopies, probe measurements, and density functional theory calculations, as the coordination site for the electron-donating propane molecules. The catalyst showed promising catalytic activity for the industrially important PDH with propane conversion of 41.8% and propylene selectivity higher than 95% and was durable during 10 successive regeneration cycles. These findings highlight a green and facile method to synthesize metal-containing zeolitic materials with regioselective metal distribution and also to open up a future perspectives for designing advanced catalysts with integrated advantages of the zeolitic matrix and metal structures.

Cobalt-Promoted Noble-Metal Catalysts for Efficient Hydrogen Generation from Ammonia Borane Hydrolysis

Ammonia borane (AB) has been regarded as a promising material for chemical hydrogen storage. However, the development of efficient, cost-effective, and stable catalysts for H₂ generation from AB hydrolysis remains a bottleneck for realizing its practical application. Herein, a step-by-step reduction strategy has been developed to synthesize a series of bimetallic species with small sizes and high dispersions onto various metal oxide supports. Superior to other non-noble metal species, the introduction of Co species can remarkably and universally promote the catalytic activity of various noble metals (e.g., Pt, Rh, Ru, and Pd) in AB hydrolysis reactions. The optimized Pt_0.1%Co_3%/TiO₂ catalyst exhibits a superhigh H₂ generation rate from AB hydrolysis, showing a turnover frequency (TOF) value of 2250 mol_H2 mol_Pt^-1 min^-1 at 298 K. Such a TOF value is about 10 and 15 times higher than that of the monometal Pt/TiO₂ and commercial Pt/C catalysts, respectively. The density functional theory (DFT) calculation reveals that the synergy between Pt and CoO species can remarkably promote the chemisorption and dissociation of water molecules, accelerating the H₂ evolution from AB hydrolysis. Significantly, the representative Pt_0.25%Co_3%/TiO₂ catalyst exhibits excellent stability, achieving a record-high turnover number of up to 215,236 at room temperature. The excellent catalytic performance, superior stability, and low cost of the designed catalysts create new prospects for their practical application in chemical hydrogen storage.

Ultrafine Pt nanoparticles anchored on core-shell structured zeolite-carbon for efficient catalysis of hydrogen generation

Ammonia borane (AB) is a potential hydrogen storage material with high-efficiency hydrolytic dehydrogenation under a suitable catalyst. Noble metal catalysts have drawn a lot of attention. In this study, a carbon-coated zeolite was obtained by calcination at high temperatures using glucose as a carbon source. Pt nanoparticles were fixed on a core-shell composite support by a simple chemical reduction method. A series of catalysts were prepared with different synthesis parameters. The results show that PSC-2 has excellent catalytic performance for hydrolytic dehydrogenation of AB in alkaline solution at room temperature, and the turnover frequency (TOF) is 593 min-1. The excellent catalytic performance is attributed to the carbon layer on the zeolite surface which inhibits the aggregation or deformation of metals in the catalytic reaction. The metal-support interaction activates the water and accelerates the rate-limiting step of hydrolysis. The activation energy (E a = 44 kJ mol-1) was calculated based on the reaction temperature. In addition, the kinetics of AB hydrolysis was studied, and the effects of catalyst concentration, AB concentration and NaOH concentration on AB hydrolysis rate were further investigated. The high-efficiency catalyst prepared in this work provides a new strategy for the development of chemical hydrogen production in the field of catalysis.

Inserting Single-Atom Zn by Tannic Acid Confinement To Regulate the Selectivity of Pd Nanocatalysts for Hydrogenation Reactions

Precisely controlling the selectivity of nanocatalysts has always been a hot topic in heterogeneous catalysis but remains difficult owing to their complex and inhomogeneous catalytic sites. Herein, an effective strategy to regulate the chemoselectivity of Pd nanocatalysts for selective hydrogenation reactions by inserting single-atom Zn into Pd nanoparticles is reported. Taking advantage of the tannic acid coating-confinement strategy, small-sized Pd nanoparticles with inserted single-atom Zn are obtained on the O-doped carbon-coated alumina. Compared with the pure Pd nanocatalyst, the Pd nanocatalyst with single-atom Zn insertion exhibits prominent selectivity for the hydrogenation of p-iodonitrobenzene to afford the hydrodeiodination product instead of nitro hydrogenation ones. Further computational studies reveal that the single-atom Zn on Pd nanoparticles strengthens the adsorption of the nitro group to avoid its reduction and increases the d-band center of Pd atoms to facilitate the reduction of the iodo group, which leads to enhanced selectivity. This work provides new guidelines to tune the selectivity of nanocatalysts with guest single-atom sites.

Partially Nitrided Ni Nanoclusters Achieve Energy-Efficient Electrocatalytic CO2 Reduction to CO at Ultralow Overpotential

Electrocatalytic CO₂ reduction reaction (CO₂ RR) offers a promising strategy to lower CO₂ emission while producing value-added chemicals. A great challenge facing CO₂ RR is how to improve energy efficiency by reducing overpotentials. Herein, partially nitrided Ni nanoclusters (NiN_x ) immobilized on N-doped carbon nanotubes (NCNT) for CO₂ RR are reported, which achieves the lowest onset overpotential of 16 mV for CO₂ -to-CO and the highest cathode energy efficiency of 86.9% with CO Faraday efficiency >99.0% to date. Interestingly, NiN_x /NCNT affords a CO generation rate of 43.0 mol g^-1  h^-1 at a low potential of -0.572 V (vs RHE). DFT calculations reveal that the NiN_x nanoclusters favor *COOH formation with lower Gibbs free energy than isolated Ni single-atom, hence lowering CO₂ RR overpotential. As NiN_x /NCNT is applied to a membrane electrode assembly system coupled with oxygen evolution reaction, a cell voltage of only 2.13 V is required to reach 100 mA cm^-2 , with total energy efficiency of 62.2%.

Encapsulating Metal Nanoparticles into a Layered Zeolite Precursor with Surface Silanol Nests Enhances Sintering Resistance

Supported metal nanoparticles are used as heterogeneous catalysts but often deactivated due to sintering at high temperatures. Confining metal species into a porous matrix reduces sintering, yet supports rarely provide additional stabilization. Here, we used the silanol-rich layered zeolite IPC-1P to stabilize ultra-small Rh nanoparticles. By adjusting the IPC-1P interlayer space through swelling, we prepared various architectures, including microporous and disordered mesoporous. In situ scanning transmission electron microscopy confirmed that Rh nanoparticles are resistant to sintering at high temperature (750 °C, 6 hrs). Rh clusters strongly bind to surface silanol quadruplets at IPC-1P layers by hydrogen transfer to clusters, while high silanol density hinders their migration based on density functional theory calculations. Ultimately, combining swelling with long-chain surfactant and utilizing metal-silanol interactions resulted in a novel, catalytically active material-Rh@IPC_C22.

Progress and Perspectives of Single-Atom Catalysts for Gas Sensing

Single-atom catalysts (SACs) attract extensive attention in the field of heterogeneous catalysis in recent years due to the maximum atom utilization and unique physical and chemical properties. The gas sensing is actually a heterogeneous catalysis process but the SACs are new to this area. Although SACs show huge potential in gas sensing, the SACs gas sensing area currently is still at the infancy stage. This work critically reviews the recent advances and current status of single-atom gas sensing materials. General synthesis routes, characterization methods, and sensing performance indexes are introduced. At the end, the challenges and future prospects on SACs gas sensing are presented from the authors' perspectives. This work is anticipated to provide insights and guideline for the chemical sensing community.