Monolithically Integrated Spinel MxCo3−xO4 (M=Co,Ni, Zn) Nanoarray Catalysts: Scalable Synthesis and Cation Manipulation for Tunable Low‐Temperature CH4 and CO Oxidation

A series of large scale M_xCo_3?xO₄ (M=Co, Ni, Zn) nanoarray catalysts have been cost‐effectively integrated onto large commercial cordierite monolithic substrates to greatly enhance the catalyst utilization efficiency. The monolithically integrated spinel nanoarrays exhibit tunable catalytic performance (as revealed by spectroscopy characterization and parallel first‐principles calculations) toward low‐temperature CO and CH₄ oxidation by selective cation occupancy and concentration, which lead to controlled adsorption–desorption behavior and surface defect population. This provides a feasible approach for scalable fabrication and rational manipulation of metal oxide nanoarray catalysts applicable at low temperatures for various catalytic reactions.     

A Molecular Approach to Self‐Supported Cobalt‐Substituted ZnO Materials as Remarkably Stable Electrocatalysts for Water Oxidation

In regard to earth‐abundant cobalt water oxidation catalysts, very recent findings show the reorganization of the materials to amorphous active phases under catalytic conditions. To further understand this concept, a unique cobalt‐substituted crystalline zinc oxide (Co:ZnO) precatalyst has been synthesized by low‐temperature solvolysis of molecular heterobimetallic Co_4?xZn_xO₄ (x=1–3) precursors in benzylamine. Its electrophoretic deposition onto fluorinated tin oxide electrodes leads after oxidative conditioning to an amorphous self‐supported water‐oxidation electrocatalyst, which was observed by HR‐TEM on FIB lamellas of the EPD layers. The Co‐rich hydroxide‐oxidic electrocatalyst performs at very low overpotentials (512 mV at pH 7; 330 mV at pH 12), while chronoamperometry shows a stable catalytic current over several hours.     

Controllable Fabrication of Tungsten Oxide Nanoparticles Confined in Graphene‐Analogous Boron Nitride as an Efficient Desulfurization Catalyst

Tungsten oxide nanoparticles (WO_xNPs) are gaining increasing attention, but low stabiliity and poor dispersion of WO_xNPs hinder their catalytic applications. Herein, WO_xNPs were confined in graphene‐analogous boron nitride (g‐BN) by a one‐step, in situ method at high temperature, which can enhance the interactions between WO_xNPs and the support and control the sizes of WO_xNPs in a range of about 4–5 nm. The as‐prepared catalysts were applied in catalytic oxidation of aromatic sulfur compounds in which they showed high catalytic activity. A balance between the W loading and the size distribution of the WO_xNPs could govern the catalytic activity. Furthermore, a synergistic effect between g‐BN and WO_xNPs also contributed to high catalytic activity. The reaction mechanism is discussed in detail and the catalytic scope was enlarged.     

CuxCo1−xO Nanoparticles on Graphene Oxide as A Synergistic Catalyst for High‐Efficiency Hydrolysis of Ammonia–Borane

Ammonia–borane (AB) is an excellent material for chemical storage of hydrogen. However, the practical utilization of AB for production of hydrogen is hindered by the need of expensive noble metal‐based catalysts. Here, we report Cu_xCo_1?xO nanoparticles (NPs) facilely deposited on graphene oxide (GO) as a low‐cost and high‐performance catalyst for the hydrolysis of AB. This hybrid catalyst exhibits an initial total turnover frequency (TOF) value of 70.0 (H₂) mol/(Cat‐metal) mol?min, which is the highest TOF ever reported for noble metal‐free catalysts, and a good stability keeping 94 % activity after 5 cycles. Synchrotron radiation‐based X‐ray absorption spectroscopy (XAS) investigations suggested that the high catalytic performance could be attributed to the interfacial interaction between Cu_xCo_1?xO NPs and GO. Moreover, the catalytic hydrolysis mechanism was studied by in situ XAS experiments for the first time, which reveal a significant water adsorption on the catalyst and clearly confirm the interaction between AB and the catalyst during hydrolysis.     

Inorganic–Organic Heteropolyacid–Gold(I) Hybrids: Structures and Catalytic Applications

Gold(I)‐polyoxometalate hybrid complexes 1 – 4 ([PPh₃AuMeCN]_xH_4?xSiW₁₂O₄₀, x=1–4) were synthesized and characterized. The structure of the primary gold(I)–polyoxometalate 1 (x=1) was fully ascertained by XRD, FTIR, ³¹P and ²⁹Si magic‐angle spinning (MAS) NMR, mass spectroscopy, and SEM–energy dispersive X‐ray spectroscopy (EDX) techniques. Moreover, this complex exhibited better catalytic activity and selectivity compared with standard, homogeneous, gold catalysts in the new rearrangement of propargylic gem‐diesters.     

Electrochemical Phase Evolution of Metal‐Based Pre‐Catalysts for High‐Rate Polysulfide Conversion

In situ evolution of electrocatalysts is of paramount importance in defining catalytic reactions. Catalysts for aprotic electrochemistry such as lithium–sulfur (Li‐S) batteries are the cornerstone to enhance intrinsically sluggish reaction kinetics but the true active phases are often controversial. Herein, we reveal the electrochemical phase evolution of metal‐based pre‐catalysts (Co₄N) in working Li‐S batteries that renders highly active electrocatalysts (CoS_x). Electrochemical cycling induces the transformation from single‐crystalline Co₄N to polycrystalline CoS_x that are rich in active sites. This transformation propels all‐phase polysulfide‐involving reactions. Consequently, Co₄N enables stable operation of high‐rate (10 C, 16.7 mA cm^?2) and electrolyte‐starved (4.7 μL mg_S^?1) Li‐S batteries. The general concept of electrochemically induced sulfurization is verified by thermodynamic energetics for most of low‐valence metal compounds.     

Easy synthesis of three‐dimensionally ordered macroporous CuO–CeO2 mixed oxide catalysts and their high activities for the catalytic combustion of soot

Three‐dimensionally ordered macroporous (3DOM) Cu_xCe‐M (x denote the mole ratio of Cu/[Ce + Cu]) oxide catalysts with large pore sizes and interconnected macroporous frameworks were successfully synthesized using a polymethyl methacrylate template method. The 3DOM structure improves the contact efficiency between catalyst and soot, which benefits soot elimination in the low temperature range. The low redox barriers of the 3DOM Cu–Ce solid solution also facilitate the elimination of the soot. The 3DOM Cu_0.1Ce catalysts exhibit the highest catalytic activity with maximum soot oxidation rate temperatures at 375 and 351 °C in the air and NO _x atmosphere, respectively. The NO _x‐TPD results demonstrate that the NO₂ produced in the Ce_0.1Cu‐M sample plays a curial role in improving the soot oxidation performance. Meanwhile, the NO‐DRIFTs reveal that the nitrates stored in the Cu_0.1Ce‐M sample also had a promotional effect on the soot elimination.     

B‐MWW Zeolite: The Case Against Single‐Site Catalysis

Boron‐containing materials have recently been identified as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins. It has previously been demonstrated by several spectroscopic characterization techniques that the surface of these boron‐containing ODH catalysts oxidize and hydrolyze under reaction conditions, forming an amorphous B₂(OH)_xO_(3?x/2) (x=0–6) layer. Yet, the precise nature of the active site(s) remains elusive. In this Communication, we provide a detailed characterization of zeolite MCM‐22 isomorphously substituted with boron (B‐MWW). Using ¹¹B solid‐state NMR spectroscopy, we show that the majority of boron species in B‐MWW exist as isolated BO₃ units, fully incorporated into the zeolite framework. However, this material shows no catalytic activity for ODH of propane to propene. The catalytic inactivity of B‐MWW for ODH of propane falsifies the hypothesis that site‐isolated BO₃ units are the active site in boron‐based catalysts. This observation is at odds with other traditionally studied catalysts like vanadium‐based catalysts and provides an important piece of the mechanistic puzzle.     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1?xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

Engineering Non‐sintered,Metal‐Terminated Tungsten Carbide Nanoparticles for Catalysis

Transition‐metal carbides (TMCs) exhibit catalytic activities similar to platinum group metals (PGMs), yet TMCs are orders of magnitude more abundant and less expensive. However, current TMC synthesis methods lead to sintering, support degradation, and surface impurity deposition, ultimately precluding their wide‐scale use as catalysts. A method is presented for the production of metal‐terminated TMC nanoparticles in the 1–4 nm range with tunable size, composition, and crystal phase. Carbon‐supported tungsten carbide (WC) and molybdenum tungsten carbide (Mo_xW_1−xC) nanoparticles are highly active and stable electrocatalysts. Specifically, activities and capacitances about 100‐fold higher than commercial WC and within an order of magnitude of platinum‐based catalysts are achieved for the hydrogen evolution and methanol electrooxidation reactions. This method opens an attractive avenue to replace PGMs in high energy density applications such as fuel cells and electrolyzers.     

Chloride‐Induced Highly Active Au Catalyst for Methyl Esterification of Alcohols

Chloride is generally regarded as a harmful species for the heterogeneous catalysts, especially Au catalysts. In this work, a series of active Au/NiO_x catalysts were successfully prepared with co‐precipitation method by tracking the concentrations of chloride in the re‐dispersed aqueous solutions. For methyl esterification of alcohols, the highest active Au/NiO_x catalysts could be prepared from aqueous solutions containing 8‐13 ppm chloride, the yield of methyl benzoate of catalyst Au/NiO_x‐9 was 99%. The catalyst structures and the role of chloride in catalysts were explored by ICP, BET, XPS, TEM and EXAFS characterizations. It was found that the appropriate amount of residual chloride in Au catalysts was beneficial to their catalytic activities. Especially for Au/NiO_x‐9, the appropriate amount of residual chloride had positive effects on the physicochemical properties of Au/NiO_x catalyst, the position of Au nanoparticles (NPs) located on NiO_x crystallites and the ratio of Au^δ+/Au⁰ in catalyst, which together resulted in its high reactivity.     

Strong Metal–Support Interactions between Copper and Iron Oxide during the High‐Temperature Water‐Gas Shift Reaction

The commercial high‐temperature water‐gas shift (HT‐WGS) catalyst consists of CuO‐Cr₂O₃‐Fe₂O₃, where Cu functions as a chemical promoter to increase the catalytic activity, but its promotion mechanism is poorly understood. In this work, a series of iron‐based model catalysts were investigated with in situ or pseudo in situ characterization, steady‐state WGS reaction, and density function theory (DFT) calculations. For the first time, a strong metal‐support interaction (SMSI) between Cu and FeO_x was directly observed. During the WGS reaction, a thin FeO_x overlayer migrates onto the metallic Cu particles, creating a hybrid surface structure with Cu‐FeO_x interfaces. The synergistic interaction between Cu and FeO_x not only stabilizes the Cu clusters, but also provides new catalytic active sites that facilitate CO adsorption, H₂O dissociation, and WGS reaction. These new fundamental insights can potentially guide the rational design of improved iron‐based HT‐WGS catalysts.     

Alkane Oxidation by an Immobilized Nickel Complex Catalyst: Structural and Reactivity Differences Induced by Surface‐Ligand Density on Mesoporous Silica

Immobilized nickel catalysts SBA*‐ L ‐x/Ni ( L =bis(2‐pyridylmethyl)(1H‐1,2,3‐triazol‐4‐ylmethyl)amine) with various ligand densities ( L content (x)=0.5, 1, 2, 4 mol % Si) have been prepared from azidopropyl‐functionalized mesoporous silicas SBA‐N₃‐x. Related homogeneous ligand LtBu and its Ni^II complexes, [Ni( LtBu )(OAc)₂(H₂O)] ( LtBu /Ni) and [Ni( LtBu )₂]BF₄ (2 LtBu /Ni), have been synthesized. The L /Ni ratio (0.9–1.7:1) in SBA*‐ L ‐x/Ni suggests the formation of an inert [Ni L ₂] site on the surface at higher ligand loadings. SBA*‐ L ‐x/Ni has been applied to the catalytic oxidation of cyclohexane with m‐chloroperbenzoic acid (mCPBA). The catalyst with the lowest loading shows high activity in its initial use as the homogeneous LtBu /Ni catalyst, with some metal leaching. As the ligand loading increases, the activity and Ni leaching are suppressed. The importance of site‐density control for the development of immobilized catalysts has been demonstrated.     

A Cheap and Efficient Methodology for the Solvent‐Free,One‐pot and Multi‐component Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones Catalyzed by Mesoporous NH4H2PO4/MCM‐48 and Comparison of Its Catalytic Efficacy with NH4H2PO4/MCM‐41

The catalytic efficiency of ammonium dihydrogenphosphate was evaluated in the two heterogeneous forms of NH₄H₂PO₄/MCM‐48 and NH₄H₂PO₄/MCM‐41, as mesoporous catalysts, in the solvent free synthesis of 3,4‐dihydropyrimidin‐2(1H)‐ones through one‐pot three‐component condensation of ethyl acetoacetate, an aryl aldehyde and urea. Different reaction parameters including catalytic efficacy, solvent effect, and urea concentration are considered.     

Three Series of Sulfo‐Functionalized Mixed‐Linker CAU‐10 Analogues: Sorption Properties,Proton Conductivity,and Catalytic Activity

Ten mixed‐linker metal–organic frameworks [Al(OH)(m‐BDC‐X)_1?y(m‐BDC‐SO₃H)_y] (H₂BDC=1,3‐benzenedicarboxylic acid; X=H, NO₂, OH) exhibiting the CAU‐10‐type structure were synthesized. The compounds can be grouped into three series according to the combination of ligands employed. The three series of compounds were obtained by employing different ratios of m‐H₂BDC‐X and m‐H₂BDC‐SO₃Li. The resulting compounds, which are denoted CAU‐10‐H/Sx, ‐N/Sx and ‐O/Sx, show exceptionally high thermal stability for sulfonated materials of up to 350 °C. Detailed characterization with special focus on polarity and acidity was performed, and the impact of the additional SO₃H groups is clearly demonstrated by changes in the sorption affinities/capacities towards several gases and water vapor. In addition, selected samples were evaluated for proton conductivity and as catalysts for the gas‐phase dehydration of ethanol to ethylene. While only very low proton conductivities were observed, a pronounced increase in catalytic activity was achieved. Although reactions were performed at temperatures of 250 and 300 °C for more than 40 h, no desulfonation and no loss of crystallinity were observed, and stable ethanol conversion resulted. This demonstrates the high stability of this material.     

g-C3N4/双钙钛矿复合材料的制备及氧催化性能

通过溶胶-凝胶法制备出不同Ni掺杂比例的双钙钛矿Sr_2Ni_xCo_(2-x)O_6(x=0.2,0.4,0.6,0.8),通过热分解法制备出具有层状结构的纳米颗粒g-C_3N_4,并制备其复合物催化剂。将双钙钛矿和g-C_3N_4分别制备成双功能电极片,用于测试其对氧还原(ORR)和氧析出(OER)的催化活性,然后选取具有最佳氧催化活性的Ni掺杂比例x=0.4的双钙钛矿与一定重量比例的g-C_3N_4进行复合,测试复合催化剂的氧催化活性。结果表明,复合后的催化剂催化效果明显优于单一催化剂,当g-C_3N_4添加量占双钙钛矿的30%(w/w)时复合催化剂催化氧还原反应的最大电流密度为395.7 mA·cm~(-2)(-0.6 V vs Hg/HgO),氧析出反应的最大电流密度为372.0mA·cm~(-2)(1 V vs Hg/HgO),这表明g-C_3N_4与Sr_2Ni_(0.4)Co_(1.6)O_6复合后协同催化能够提高双钙钛矿的氧催化活性。     

Dual functional novel catalytic Cu1−xZrxFe2O4 (x=0, 0.5, 1) nanoparticles for synthesis of polysubstituted pyridines and sunlight‐driven degradation of methylene blue

The effect of varied zirconium content on the structural, morphological, magnetic, optical, thermal and catalytic properties of nanoparticles of the ferrite Cu_1 ? xZr_xFe₂O₄ (x = 0, 0.5, 1) was investigated. The mixed ferrite was synthesized by the auto‐combustion method using nitrates of respective metals and citric acid as a chelating agent. The as‐prepared nanoparticles showed dual benefits. They were employed as a heterogeneous catalyst for one‐pot synthesis of polysubstituted pyridine derivatives as well as for catalytic degradation of industrial waste dyes such as methylene blue (MB). The highlight of the research reported is the catalytic degradation of industrial waste (MB) with high efficiency in eluent of a wide range of pH (3–13). The proposed nanoparticles arguably offer certain great advantages that include: low cost, facile nature, anti‐leaching property, magnetic recoverability and recyclability. The characterization of the as‐synthesized nanoparticles was done using various techniques. The leaching study was carried out using inductively coupled plasma optical emission spectroscopy. The formation of organic products was confirmed using Fourier transform infrared and ¹H NMR spectroscopies and examination of degradation products of MB dye was carried out using mass spectrometry and UV–visible spectroscopy.     

Large‐scale Two‐dimensional MoSx Catalyst Prepared under Mild Conditions for Enhancing Electrocatalytic Hydrogen Evolution Reaction

As an electrocatalyst with abundant resources and great potential, molybdenum disulfide is regarded as one of the most likely alternatives to expensive noble‐metals catalysts. However, it is still a challenge to achieve large scale production of few‐layer MoS₂ with enhancing activity of electrocatalytic hydrogen reaction at ambient conditions. Herein, we developed a simple environmentally friendly two‐step method, which included intercalation reaction and a subsequent electrochemical reduction reaction for mass preparation of defect‐rich desulfurized MoS_x (D?MoS_x) nanosheets with plentiful sulfur vacancies. The ratio of sulfur‐molybdenum atoms can be adjusted from 2 : 1 to 1.4 : 1 by regulating the desulfurization voltage. It was found that the HER catalytic activity of the D?MoS_x was enhanced compared with that of pristine MoS₂ (P?MoS₂), the current density of D?MoS_x (desulfurization at ?1.0 V) at ?0.3 V versus RHE was about 169% of the P?MoS₂, and the Tafel slope decreased to 136 mV dec^?1. This method can be widely applied to large‐scale preparation of other two‐dimensional materials.     

Silicotungstic acid modified Ce‐Fe‐Ox catalyst for selective catalytic reduction of NOx with NH3: Effect of the amount of HSiW

The HSiW(x)/Ce‐Fe catalysts were used to research the effect of silicotungstic acid contents on the catalytic activity in the selective catalytic reduction of NO_x with NH₃. Doping different contents of silicotungstic acid affected surface species and redox property as well as the catalytic activity. With the increasing amount of HSiW (x = 5%, 10% and 20%), the redox reaction between Fe³⁺/Fe²⁺ and Ce⁴⁺/Ce³⁺ enhanced, which could improve the ratio of Ce³⁺ and Fe³⁺. And then, more Ce³⁺ increased the ratio of chemisorbed oxygen (O_α). Besides, the type and strength of acid sites over HSiW(_x)/Ce‐Fe was affected by the HSiW contents. These factors facilitated the catalytic performance. Thus, the NO_x conversion of HSiW(x)/Ce‐Fe(x = 20%) was higher than 90%, which maintained in a wide temperature range between 200 and 400 °C.     

Identification of Catalytic Sites for Oxygen Reduction in Metal/Nitrogen‐Doped Carbons with Encapsulated Metal Nanoparticles

The development of metal‐N‐C materials as efficient non‐precious metal (NPM) catalysts for catalysing the oxygen reduction reaction (ORR) as alternatives to platinum is important for the practical use of proton exchange membrane fuel cells (PEMFCs). However, metal‐N‐C materials have high structural heterogeneity. As a result of their high‐temperature synthesis they often consist of metal‐N_x sites and graphene‐encapsulated metal nanoparticles. Thus it is hard to identify the active structure of metal‐N‐C catalysts. Herein, we report a low‐temperature NH₄Cl‐treatment to etch out graphene‐encapsulated nanoparticles from metal‐N‐C catalysts without destruction of co‐existing atomically dispersed metal‐N_x sites. Catalytic activity is much enhanced by this selective removal of metallic nanoparticles. Accordingly, we can confirm the spectator role of graphene‐encapsulated nanoparticles and the pivotal role of metal‐N_x sites in the metal‐N‐C materials for ORR in the acidic medium.