NiCo-sulfide hetero-structured interface induced highly active nickel-dominated metal sites for oxygen evolution reaction

The development of sustainable energy is of great significance for relieving the energy shortage crisis, where the oxygen evolution reaction (OER) in water electrolysis plays a crucial role in efficient energy conversion technology. Hetero-structured transition metal sulfides are regarded as quite promising electrocatalytic materials, considering their intrinsic activity and prominent synergistic effect. However, the essential surface reconstruction process of transition metal sulfides renders a great challenge to reveal the real active sites and the relative electrocatalytic reaction mechanism. Herein, novel sea urchin-like NiCo bimetallic sulfide (denoted as NiS/Co₃S₄) catalysts with highly exposed heterogeneous interface is designed for efficient OER. The high electrochemical active surface as well as effectual charge-transfer effect ensures NiS/Co₃S₄ catalysts with superior activity and durability, such as a low overpotential of 285 mV at 100 mA/cm², a small Tafel slope of 66 mV/dec as well as the long-term stability for 60 h. The post OER characterizations confirm that high valence of Ni dominated metal sites expedite the surface reconstruction process and the formed Ni (oxy)hydroxides significantly accelerate the process of oxygen evolution reaction.     

Design of efficient noble metal single-atom and cluster catalysts toward low-temperature preferential oxidation of CO in H2

The preferential oxidation of CO in H₂ is attractive for the removal of trace amounts of CO to meet the requirement of proton-exchange membrane fuel cells (PEMFCs) application. The key is to design highly effective catalysts that work well in a wide range of low temperatures. Here, the recent progress in Au and Pt group metal catalysts for the PROX reaction is summarized, covering those with single-atom and cluster dispersed metal species with remarkable performance. Firstly, the progress of some representative catalysts is overviewed, with an emphasis on the strategies for improving low-temperature activity, selectivity, and stability. Then, special attention is focused on the key parameters affecting performance in the PROX reaction. Moreover, the reaction mechanisms in terms of adsorption and activation of reactants are discussed. Finally, the challenges and opportunities are offered for guiding the design of advanced noble metal catalysts toward the PROX process.     

Engineering high-entropy materials for electrocatalytic water splitting

The multicomponent combinations of metals in nanoscale noble metal-free high-entropy materials possess distinctive physiochemical properties, which endow them with rich accessible active sites, strong synergistic effect, and entropy-stabilization effect, enabling them to be promising for driving electrocatalytic water splitting. Herein, an interview of the progress achieved for the synthesis of noble metal-free high-entropy materials and catalytic mechanisms toward water splitting is provided. Some typical synthesis strategies have been systematically reviewed to highlight the advances in synthesizing highly efficient and noble-metal-free high-entropy catalysts. Next, the distinctive advantages of high-entropy materials for the electrochemical water splitting are also manifested to show their great promise for serving as advanced electrocatalysts. Moreover, some representative examples regarding the electrocatalytic oxygen evolution reaction, hydrogen evolution reaction, and overall water splitting based on noble-metal-free high-entropy catalysts are also discussed. In the end, future directions and new energy conversion technologies that can be enabled by the application of noble-metal-free high-entropy materials are outlined.     

Advances in the implementation of PVD-based techniques for the preparation of metal catalysts for the hydrolysis of sodium borohydride

Sodium borohydride constitutes a safe alternative for the storage of hydrogen with a high gravimetric content. Catalytic hydrolysis of sodium borohydride permits on-demand hydrogen generation for multiple applications. In this field, the rational design of efficient metal catalysts deposited on structured supports is highly desirable. For most reactions, chemical methods are the most commonly used methods for the preparation of supported metal catalysts. Physical vapour deposition techniques are emerging as an alternative for the preparation of catalytic materials because of their multiple advantages. They permit the one-step deposition of catalysts on structured supports with controlled microstructure and composition, avoiding the multi-step procedures and the generation of hazardous by-products associated with chemical routes.In this short review, we will describe the available literature on the application of physical vapour deposition techniques for the preparation of supported metal catalysts for the hydrolysis of sodium borohydride. The effects of the deposition parameters on the properties of the catalytic materials will be discussed, and strategies for further improvement will be proposed. Here, we also present our new results on the study of nanoporous Pt catalysts that are prepared through the chemical dealloying of magnetron-sputtered Pt–Cu thin films for the hydrolysis of sodium borohydride. We discuss the capabilities of the technique to tune the microstructure from columnar to closed porous microstructures, which, coupled with dealloying, produces more active supported catalysts with lower noble metal loading. At the end, we briefly mention the application of PVD for the preparation of supported catalysts for the hydrolysis of ammonia borane, another hydrogen generating reaction of high interest nowadays.     

用于柴油机尾气脱硫捕集器的干式脱硫材料研究进展

柴油机尾气处理系统中脱除氮氧化合物（NOx）的催化剂易受硫的侵蚀而中毒。为避免SOx对净化NOx催化剂的毒害作用,一种有效的解决办法是将脱硫捕集器置于脱除NOx催化剂的系统之前来捕获柴油机尾气中的氧化硫（SOx）。本文针对贵金属催化剂、金属碳酸盐、金属氧化物等几种主要应用于柴油机脱硫捕集器的干式脱硫材料,主要阐述了各自的脱硫原理及性能,并分析了各种脱硫材料的研究现状和工业化应用前景,并指出了高性能且价格低廉的金属氧化物是未来应用于柴油机脱硫捕集器的主要方向。     

A review of heteroatomic doped two-dimensional materials as electrocatalysts for hydrogen evolution reaction

Emerging two-dimensional (2D) materials, such as graphene, transition metal disulfide compounds (TMDCs), MXenes, layer double hydroxides (LDHs), black phosphorus (BP) and hexagonal boron nitride (h-BN), play an important role in speeding up hydrogen evolution reaction (HER) due to its large specific surface area as well as function of loading and efficient support. However, as an electrocatalyst, pure 2D materials cannot meet HER needs caused by their monotonous performance. Therefore, some nanoparticles are used to load and tune the 2D materials to develop efficient and inexpensive catalysts. Herein, we conduct a thorough analysis for materials based on heteroatoms, especially transition metal atoms and non-metal atoms (N, P, S, etc.) doped with graphene, TMDCs, MXenes, LDHs, BP and h-BN. It can be found that doping or coupling between 2D materials will affect the electronic structure, energy band, active area, conductivity and stability of the catalyst, which will induct a huge change in the catalytic performance. This review reveals the relationship between active centers, H₂O adsorption and chemical reaction processes. It also analyzes and summarizes the design principles and performance improvement mechanisms of hybrid catalysts. These discussions can provide references for other researchers to develop derivatives of related catalysts.     

Facile synthesis of efficient core-shell structured iron-based carbon catalyst for oxygen reduction reaction

Controlled synthesis of efficient core-shell non-precious metal catalysts for oxygen reduction reaction (ORR) is undoubtedly crucial but challenging for the extensive application of fuel cells and metal-air batteries. Herein, we prepared a core-shell structured Fe/FeC_x nanoparticles and porous carbon composited catalyst (Fe/FeC_x@NC) via a facile two-step heat treatment strategy. The Fe/FeC_x@NC-800_?0.5 prepared with secondary anneal at 800 °C for 0.5 h exhibits superior ORR performance to the commercial Pt/C in terms of comparable onset potential, higher half-wave potential, and outstanding long-term durability in alkaline media. Through combining the physical and electrochemical characterizations of Fe/FeC_x@NC-T_?t with different anneal temperature and precursors, the outstanding ORR performance of Fe/FeC_x@NC-800_?0.5 is caused by the synergistic effect between Fe/FeC_x core and enriched pyridinic N- and graphitic N-doped carbon shell as well as porous carbon with large specific surface area. The structure-activity relationship of core-shell structured Fe–N–C catalysts for ORR provides directions for the development of advanced nonprecious metals catalysts.     

A series of Ni–Al2O3 catalysts derived from layered double hydroxides for vapor phase catalytic exchange between water and hydrogen

Fabricating supported metal catalysts from layered double hydroxides (LDHs) is a promising strategy to develop high-efficient and low-cost materials for water detritiation. In this work, a series of NiAl-LDHs with different Ni/Al ratios were prepared and reduced to obtain Ni-based catalysts with Al₂O₃ support (Ni_x-Al₂O₃) and further tested in vapor phase catalytic exchange (VPCE) process. Results revealed that the activity of catalysts varies with Ni/Al molar ratios and is also affected by textural properties. Remarkably, the Ni₂–Al₂O₃ with the Ni/Al molar ratio of 2 exhibited excellent activity, due to the balanced factors of Ni content, specific surface area, Ni particle size and Al³⁺ configuration proportion. This study sheds some light on reaction mechanism of VPCE process and may be applicable for the rational design of highly efficient catalysts.     

纤维素制备异山梨醇研究进展

异山梨醇可由资源丰富的纤维素直接转化制得,是一种重要的精细化学品,对未来化石能源产品的替代具有重要意义。本文从纤维素转化制备异山梨醇的反应路径、工艺方法、催化剂体系及催化性能影响因素几个方面进行综述,简述纤维素制异山梨醇工艺方法中多步反应与一步反应工艺的区别,论述反应所用二元催化剂及双功能催化剂的特性,分析催化剂酸量、金属粒径及孔道结构对反应性能的影响。概括纤维素催化转化制异山梨醇已取得的进展以及目前仍存在的一些问题,在此基础上对纤维素转化制异山梨醇反应催化剂的孔道结构、金属活性位、酸活性位设计及纤维素原料等进行展望,以期为后续研究提供参考。     

Low metal content Co and Ni alumina supported catalysts for the CO2 reforming of methane

Low metal content Co and Ni alumina supported catalysts (4.0, 2.5 and 1.0 wt% nominal metal content) have been prepared, characterized (by ICP-OES, TEM, TPR-H₂ and TPO) and tested for the CO₂ reforming of methane. The objective is to optimize the metal loading in order to have a more efficient system. The selected reaction temperature is 973 K, although some tests at higher reaction temperature have been also performed. The results show that the amount of deposited carbon is noticeably lower than that obtained with the Co and Ni reference catalysts (9 wt%), but the CH₄ and CO₂ conversions are also lower. Among the catalysts tested, the Co(1) catalyst (the value in brackets corresponds to the nominal wt% loading) is deactivated during the first minutes of reaction because CoAl₂O₄ is formed, while Ni(1) and Co(2.5) catalysts show a high specific activity for methane conversion, a high stability and a very low carbon deposition.     

生物质到生物燃料—费托合成催化剂的研究进展

费托合成反应是煤、甲烷和生物质等非油基碳资源转化制高品质液体燃料或化学品的重要途径。以生物质基合成气为原料,利用传统的Fe、Co催化剂制备生物燃料引起普遍关注。本文简要总结了近年来高性能Fe基和Co基费托合成催化剂的发展,以及近年来新型材料和核壳结构的双功能催化剂在费托合成中的应用。重点关注了生物质合成气方面的应用,比较了Fe、Co催化剂在该应用中的特点。虽然Co基催化剂较Fe基催化剂有更好的活性,但在BTL（Biomass-To-Liquid）过程中需要考虑多种因素,Fe基催化剂可能更具优势,开发廉价高性能的Fe基催化剂可能成为BTL-FT催化剂的发展方向。     

Facile fabrication of PtPd alloyed worm-like nanoparticles for electrocatalytic reduction of oxygen

Alloying platinum with a second metal such as palladium can increase the mass activity of Pt and lower the usage of expensive Pt elements, hence is of great importance for designing highly efficient and cost-effective electrocatalysts for oxygen reduction reaction (ORR). In this study, monomorphic PtPd alloyed worm-like nanoparticles (PtPd WNPs) with dominant (111) facets were prepared with a facile one-pot approach. The detailed morphology, composition, and surface structure of the PtPd WNPs were investigated by transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), X-ray diffraction (XRD), as well as X-ray photoelectron spectroscopy (XPS). The prepared PtPd WNPs displayed enhanced electrocatalytic activity and remarkably robust stability toward ORR in both alkaline and acidic media, superior than commercial Pt/C catalysts. This strategy may open a new route to design and prepare advanced electrocatalysts for fuel cells.     

Effect of the CeO2 synthesis method on the behaviour of Pt/CeO2 catalysis for the water-gas shift reaction

A comparative study of three different ceria synthesis procedures (template- and MW- assisted hydrothermal synthesis and urea homogeneous precipitation) is reported in this paper. The obtained materials were employed as supports for Pt nanoparticles, and the Pt/CeO₂ catalysts were evaluated in the WGS reaction under model and realistic conditions. The influence of the support, e.g., its morphology and electronic properties, has been studied in detail by means of XRD, H₂-TPR, XPS, UV–Vis spectroscopy and toluene hydrogenation (for metal dispersion assessment). The catalytic performance of the samples is directly correlated with the modification of the electronic properties, as a result of the preparation method used. The conventional homogeneous precipitation method with urea resulted to be the best option, leading to enhanced ceria reducibility and adequate Pt dispersion, which in turns resulted in a very efficient WGS catalyst.     

Highly active Cu-ZnO catalysts for the WGS reaction at medium–high space velocities: Effect of the support composition

Cu-ZnO based catalysts are the benchmark materials for the low-temperature WGS reaction. However, they present a crucial drawback which limits their application in portable devices: they only work under very low space velocities. In this study, we have developed a series of multicomponent Cu-ZnO catalysts able to work at relatively high space velocities with outstanding activity and stability. Different reference supports have been utilised with CeO₂-Al₂O₃ being the most promising system. Overall, this work describes a strategy to design advanced Cu-based catalysts that can overcome the residence time restrictions in the WGS reaction.     

Metal-organic-framework-derived metals and metal compounds as electrocatalysts for oxygen evolution reaction: A review

Electricity-driven oxygen evolution reaction (OER) is crucial for water dissociation because it allows for sustainable and clean energy production. However, the fast reaction should be improved for industrial applications. Therefore, numerous studies have focused on designing and synthesizing high-performance catalysts with low-cost facial processes for use in the OER. Metal-organic frameworks are hybrid materials that consist of inorganic and organic components, exemplified as ideal sacrificial templates for the fabrication of efficient anode materials to be used in water oxidation. In this account, various types of MOF-derived anode materials, including metals, metal oxides, metal phosphides, nitrides, carbides, and metal chalcogenides, are discussed. In addition, we have demonstrated the advantages of MOFs and provide studies with controverted mechanisms of the OER. Finally, the current problems and prospects for the use of MOFs in the electrochemical OER are discussed.     

Efficient valorization of biomass to biofuels with bifunctional solid catalytic materials

Mono-functional catalytic materials are used for many types of chemical transformations, but are tedious for delivering products from multiple-step reactions required for the valorization of biomass. An emerging trend is to integrate catalytic transformations, reaction engineering and product separation into a single operation, wherein catalyst design is considered as the key approach to develop efficient, low energy and environmentally-friendly reaction systems. Bifunctional solid catalysts open a door for carrying out domino/cascade- and tandem/sequential-type reactions in a single pot, for which the number of isolation or purification steps can be lessened or eliminated so that removal of unwanted by-products becomes unnecessary. This review introduces bifunctional materials used in one-pot multiple transformations of biomass into biofuels and related chemicals. Emphasis is placed on the assessment of the bifunctionality of catalytic materials, including Bronsted–Lewis acid, acid–base, and metal particles–acid or base bifunctional catalysts with some discussion being on combined catalytic systems with electrochemical, chemo-enzymatic and photochemical methods. Plausible reaction mechanisms for key pathways are shown. Relevant auxiliaries to boost catalytic activity and product selectivity, such as reaction media, heating modes and morphological properties of the catalytic materials are analyzed. Use of appropriate bifunctional catalytic materials provides many opportunities for design of highly efficient reaction systems and simplified processing for producing biofuels and chemicals from lignocellulosic biomass.     

Facile and eco-friendly synthesis of porous carbon nanosheets as ideal platform for stabilizing rhodium nanoparticles in efficient hydrolysis of ammonia borane

Carbon materials have been demonstrated as excellent carriers for preparing supported metal nanocatalysts in catalytic applications. However, numerous chemical activators including strong acids and bases were applied, leading to the entire process dangerous and hazardous. Eco-friendly, economic, and convenient synthesis of carbon materials with desired properties as supports for metal nanoparticle (NP) stabilization to boost performance is important but remains challenging. Here, we developed a facile and eco-friendly strategy to synthesize porous carbon nanosheets (PCNs) with ultrahigh specific surface area (2575.1 m²/g) via pyrolysis the mixture of potassium oxalate and glucose. The resultant PCNs can be used as ideal platform for in-situ distribution of small Rh NPs (Rh/PCNs) as efficient catalysts in hydrogen production from ammonia borane (AB) under ambient conditions. Specifically, Rh/PCNs displayed high activity for AB hydrolysis, with a turnover frequency (TOF) of 513.2 min⁻¹. Small and well-distributed Rh NPs on PCNs with large catalytically active surface atoms are contributed to the high catalytic property of Rh/PCNs for the reaction. Present study has demonstrated that the PCNs is a superior catalyst support for preparing a series of metal NPs in other catalytic applications beyond hydrolysis reaction.     

Functionalizing carbon nanotubes for proton exchange membrane fuel cells electrode

In recent years, carbon nanotubes (CNTs) have been increasingly considered as an advanced metal catalyst support for proton exchange membrane fuel cells (PEMFCs), owing to their outstanding physical and mechanical characteristics. However, the effective attachment of metal catalysts, uniformly dispersed onto the CNT surface, remains a formidable challenge because of the inertness of the CNT walls. Therefore, the surface functionalization of CNTs seems necessary in most cases in order to enable a homogeneous metal deposition. This review presents the different surface functionalization approaches that provide efficient avenues for the deposition of metal nanoparticles on CNTs, for the application of catalyst supports in PEMFCs with improved reactivity.     

On-board methanol catalytic reforming for hydrogen Production-A review

Hydrogen has become a versatile and clean alternative to meet increasingly urgent energy demands since its high heating value and renewability. However, considering the hazards of hydrogen storage and transport, in-situ production processes are drawing more attention. Among all the hydrogen carriers, methanol has become one of the research focuses due to its high H/C ratio, flexibility and sustainability. Regarded as the core of hydrogen supply system, catalysts with higher activity, selectivity and stability are continuously developed for improved efficiency. In this review, two groups of catalysts were investigated namely copper-based and group VIII metal-based catalysts. Not only macro indicators such as feedstock conversion and product selectivity, but also micro interaction and reaction mechanism were elaborated, with respect to the effects of promoters, supports, synthesis methods and binary metal components. Notably, several reaction pathways and catalysts deactivation mechanisms were suggested based on this series of inspection of the structure-reactivity relationship, along with a general perception that large surface area, well dispersed metals, small particle size and synergy effects significantly improve the catalytic performance. Accordingly, a novel concept of single-atom catalysts (SACs) was introduced aimed at efficient hydrogen production under more moderate conditions, by combining the advantages of heterogeneous and homogeneous catalysis. Additionally, an efficient reforming process is required by properly regulating the feed flow and heat flow through a coupled system. Conclusively, a thorough supply and demand network of hydrogen based on methanol was presented, giving an overview for on-board applications of hydrogen energy.     

A comprehensive review on improving the production of rich-hydrogen via combined steam and CO2 reforming of methane over Ni-based catalysts

During the last few decades, the global energy requirement is soaring significantly due to the rise of global population and economic development. This resulted in colossal release of CO₂ and CH_4, emissions into the atmosphere referred as greenhouse gases (GHGs), which poses a detrimental effects for the environment. One of the sustainable solutions to curb emissions of GHGs into the atmosphere is efficient utilization of syngas in order to produce useful chemicals and fuels. A comprehensive review is presented to highlight the capability of Ni-based catalysts in methane reforming through the application of both steam and dry routes referred to as bi-reforming of methane (BRM). Ni-based catalysts were found to support favorable reaction activity as they are cheaper than many exorbitant catalysts. The metal used for catalyst support exhibits higher stability and thermal resistance with improved resistance to coke formation. This review entails recent progresses in the development of Ni-based catalysts along with physical and kinetic aspects of the BRM process.