Investigation of the Support Effect in Atomically Dispersed Pt on WO3−x for Utilization of Pt in the Hydrogen Evolution Reaction

Single‐atom catalysts (SACs) have attracted growing attention because they maximize the number of active sites, with unpredictable catalytic activity. Despite numerous studies on SACs, there is little research on the support, which is essential to understanding SAC. Herein, we systematically investigated the influence of the support on the performance of the SAC by comparing with single‐atom Pt supported on carbon (Pt SA/C) and Pt nanoparticles supported on WO_3?x (Pt NP/WO_3?x). The results revealed that the support effect was maximized for atomically dispersed Pt supported on WO_3?x (Pt SA/WO_3?x). The Pt SA/WO_3?x exhibited a higher degree of hydrogen spillover from Pt atoms to WO_3?x at the interface, compared with Pt NP/WO_3?x, which drastically enhanced Pt mass activity for hydrogen evolution (up to 10 times). This strategy provides a new framework for enhancing catalytic activity for HER, by reducing noble metal usage in the field of SACs.     

Polymeric Carbon Nitride/Mesoporous Silica Composites as Catalyst Support for Au and Pt Nanoparticles

Small and homogeneously dispersed Au and Pt nanoparticles (NPs) were prepared on polymeric carbon nitride (CN_x)/mesoporous silica (SBA‐15) composites, which were synthesized by thermal polycondensation of dicyandiamide‐impregnated preformed SBA‐15. By changing the condensation temperature, the degree of condensation and the loading of CN_x can be controlled to give adjustable particle sizes of the Pt and Au NPs subsequently formed on the composites. In contrast to the pure SBA‐15 support, coating of SBA‐15 with polymeric CN_x resulted in much smaller and better‐dispersed metal NPs. Furthermore, under catalytic conditions the CN_x coating helps to stabilize the metal NPs. However, metal NPs on CN_x/SBA‐15 can show very different catalytic behaviors in, for example, the CO oxidation reaction. Whereas the Pt NPs already show full CO conversion at 160 °C, the catalytic activity of Au NPs seems to be inhibited by the CN_x support.     

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.     

Synthesis of Ni–Ru Alloy Nanoparticles and Their High Catalytic Activity in Dehydrogenation of Ammonia Borane

We report the synthesis and characterization of new Ni_xRu_1?x (x=0.56–0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet‐chemistry method using a rapid lithium triethylborohydride reduction of Ni²⁺ and Ru³⁺ precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X‐ray spectroscopy (EDX), and X‐ray photoelectron spectroscopy (XPS). We found that the as‐prepared Ni–Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni–Ru alloy NPs, and in particular the Ni_0.74Ru_0.26 sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core‐shell NPs. The hydrolysis activation energy for the Ni_0.74Ru_0.26 alloy catalyst was measured to be approximately 37 kJ mol^?1. This value is considerably lower than the values measured for monometallic Ni (≈70 kJ mol^?1) and Ru NPs (≈49 kJ mol^?1), and for Ni@Ru (≈44 kJ mol^?1), and is also lower than the values of most noble‐metal‐containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

Relating the Composition of PtxRu100−x/C Nanoparticles to Their Structural Aspects and Electrocatalytic Activities in the Methanol Oxidation Reaction

A controlled composition‐based method—that is, the microwave‐assisted ethylene glycol (MEG) method—was successfully developed to prepare bimetallic Pt_xRu_100?x/C nanoparticles (NPs) with different alloy compositions. This study highlights the impact of the variation in alloy composition of Pt_xRu_100?x/C NPs on their alloying extent (structure) and subsequently their catalytic activity towards the methanol oxidation reaction (MOR). The alloying extent of these Pt_xRu_100?x/C NPs has a strong influence on their Pt d‐band vacancy and Pt electroactive surface area (Pt ECSA); this relationship was systematically evaluated by using X‐ray absorption (XAS), scanning electron microscopy (SEM) coupled with energy dispersive X‐ray spectroscopy (EDX), transmission electron microscopy (TEM), density functional theory (DFT) calculations, and electrochemical analyses. The MOR activity depends on two effects that act in cooperation, namely, the number of active Pt sites and their activity. Here the number of active Pt sites is associated with the Pt ECSA value, whereas the Pt‐site activity is associated with the alloying extent and Pt d‐band vacancy (electronic) effects. Among the Pt_xRu_100?x/C NPs with various Pt:Ru atomic ratios (x=25, 50, and 75), the Pt₇₅Ru₂₅/C NPs were shown to be superior in MOR activity on account of their favorable alloying extent, Pt d‐band vacancy, and Pt ECSA. This short study brings new insight into probing the synergistic effect on the surface reactivity of the Pt_xRu_100?x/C NPs, and possibly other bimetallic Pt‐based alloy NPs.     

Selectively Chemocatalytic Conversion of Fructose to 1,2‐Propylene Glycol over Ru‐WOx/Hydroxyapatite Catalyst†

The conversion of fructose to 1,2‐propylene glycol (PG) is an important process from cellulosic biomass to high‐value added chemicals. Herein, Ru‐WO_x/hydroxyapatite (HAP) catalyst was employed for this reaction and reached up to 91.3% yield of PG at 180 °C, 1 MPa initial hydrogen for 8 h in water. On this catalyst, Ru and WO_x were highly dispersed on HAP support and they interacted with each other to form a special catalytic center. The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol. The weak basic HAP support efficiently prevented the humin formation. This precisely controlled catalyst has potential in green PG production.     

Promotional effect of acidic oxide on catalytic activity and N2 selectivity over CeO2 for selective catalytic reduction of NOx by NH3

The CeO₂, CeO₂‐ZrO₂ and CeO₂‐WO₃ catalysts were prepared by hydrothermal method and used to the selective catalytic reduction of NO_x by NH₃. The addition of ZrO₂ or WO₃ into CeO₂ was favorable for pore structure, and then improved the number of active sites. Besides, the introduction of ZrO₂ into CeO₂ could improve the Lewis acid sites while WO₃ could contribute to the generation of Brønsted and Lewis acid sites, which could improve the catalytic performance and N₂ selectivity. The CeO₂‐WO₃ catalyst exhibited optimal catalytic activity with above 90% NO_x conversion performance at 220–425 °C and approximately 100% N₂ selectivity at 150–425 °C.     

Structure Evolution and Associated Catalytic Properties of PtSn Bimetallic Nanoparticles

Bimetallic nanoparticles (NPs) often show new catalytic properties that are different from those of the parent metals. Carefully exploring the structures of bimetallic NPs is a prerequisite for understanding the structure‐associated properties. Herein, binary Pt?Sn NPs with tunable composition are prepared in a controllable manner. X‐ray characterizations reveal that their structures evolve from SnO_2?x‐patched PtSn alloys to SnO_2?x‐patched Pt clusters when more tin is incorporated. An obvious composition‐dependent catalytic performance is observed for the hydrogenation of α,β‐unsaturated aldehydes: the selectivity to unsaturated alcohol increases substantially at high tin content, whereas the reaction rate follows a volcano shape. Furthermore, Pt sites are responsible for hydrogen dissociation, whereas oxygen vacancy (O_vac) sites, provided by SnO_2?x, drastically enhance the adsorption of carbonyl group.     

An In Situ Carbonization–Replication Method to Synthesize Mesostructured WO3/C Composite as Nonprecious‐Metal Anode Catalyst in PEMFC

A meostructured WO₃/C composite with crystalline framework and high electric conductivity has been synthesized by a new in situ carbonization–replication route using the block copolymer (poly(ethylene glycol)‐block‐poly(propylene glycol)‐block‐poly(ethylene glycol)) present in situ in the pore channels of mesoporous silica template as carbon source. X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, thermogravimetry differential thermal analysis, and N₂ adsorption techniques were adopted for the structural characterization. Cyclic voltammetry, chronoamperometry, and single‐cell test for hydrogen electrochemical oxidation were adopted to characterize the electrochemical activities of the mesoporous WO₃/C composite. The carbon content and consequent electric conductivity of these high‐surface‐area (108–130 m² g^?1) mesostructured WO₃/C composite materials can be tuned by variation of the duration of heat treatment, and the composites exhibited high and stable electrochemical catalytic activity. The single‐cell test results indicated that the mesostructured WO₃/C composites showed clear electrochemical catalytic activity toward hydrogen oxidation at 25 °C, which makes them potential non‐precious‐metal anode catalysts in proton exchange membrane fuel cell.     

Palladium Nanoparticles Supported on Titanium‐Doped Graphitic Carbon Nitride for Formic Acid Dehydrogenation

Pd nanoparticles (NPs) supported on Ti‐doped graphitic carbon nitride (g‐C₃N₄) were synthesized by a deposition–precipitation route and a subsequent reduction with NaBH₄. The features of the NPs were studied by XRD, TEM, FTIR, XPS, EXAFS and N₂‐physisorption measurements. It was found that the NPs had an average size of 2.9 nm and presented a high dispersion on the surface of Ti‐doped g‐C₃N₄. Compared to Pd loaded on pristine g‐C₃N₄, the Pd NPs supported on Ti‐doped g‐C₃N₄ exhibited a high catalytic activity in formic acid dehydrogenation in water at room temperature. The enhanced activity could be attributed to the small Pd NPs size, as well as the strong interaction between Pd NPs and Ti‐doped g‐C₃N₄.     

Facile Preparation of WO3−x Dots with Remarkably Low Toxicity and Uncompromised Activity as Co‐reactants for Clinical Diagnosis by Electrochemiluminescence

The exceptional nature of WO_3?x dots has inspired widespread interest, but it is still a significant challenge to synthesize high‐quality WO_3?x dots without using unstable reactants, expensive equipment, and complex synthetic processes. Herein, the synthesis of ligand‐free WO_3?x dots is reported that are highly dispersible and rich in oxygen vacancies by a simple but straightforward exfoliation of bulk WS₂ and a mild follow‐up chemical conversion. Surprisingly, the WO_3?x dots emerged as co‐reactants for the electrochemiluminescence (ECL) of Ru(bpy)₃²⁺ with a comparable ECL efficiency to the well‐known Ru(bpy)₃²⁺/tripropylamine (TPrA) system. Moreover, compared to TPrA, whose toxicity remains a critical issue of concern, the WO_3?x dots were ca. 300‐fold less toxic. The potency of WO_3?x dots was further explored in the detection of circulating tumor cells (CTCs) with the most competitive limit of detection so far.     

Ultrathin,Porous and Oxygen Vacancies‐Enriched Ag/WO3−x Heterostructures for Electrocatalytic Hydrogen Evolution

Exploring advanced electrocatalysts for electrocatalytic hydrogen evolution is highly desired but remains a challenge due to the lack of an efficient preparation method and reasonable structural design. Herein, we deliberately designed novel Ag/WO_3?x heterostructures through a supercritical CO₂‐assisted exfoliation‐oxidation route and the subsequent loading of Ag nanoparticles. The ultrathin and oxygen vacancies‐enriched WO_3?x nanosheets are ideal substrates for loading Ag nanoparticles, which can largely increase the active site density and improve electron transport. Besides, the resultant WO_3?x nanosheets with porous structure can form during the electrochemical cycling process induced by an electric field. As a result, the exquisite Ag/WO_3?x heterostructures show an enhanced hydrogen evolution reaction (HER) activity with a low onset overpotential of ≈30 mV, a small Tafel slope of ≈40 mV dec^?1 at 10 mA cm^?2, and as well as long‐term durability. This work sheds light on material design and preparation, and even opens up an avenue for the development of high‐efficiency electrocatalysts.     

Chemoselective hydrogenation of phenol to cyclohexanol using heterogenized cobalt oxide catalysts

Cobalt oxide nanoparticles (NPs) supported on porous carbon (CoO_x@CN) were fabricated by one-pot method and the hybrids could efficiently and selectively hydrogenate phenol to cyclohexanol with a high yield of 98%.     

铂-氢钨青铜电极的制备及对氢氧化的电催化

采用电化学还原法在表面改性的碳布上,通过改变催化剂沉积顺序及氢钨青铜沉积时间制备铂-氢钨青铜复合催化剂,所得电极作为质子交换膜燃料电池(PEMFC)阳极。利用X射线衍射(XRD)、热重分析(TG)、扫描电子显微镜(SEM)、循环伏安(CV)及单电池极化性能测试研究了催化剂的组成、沉积量、分散性及其对氢氧化的电催化活性。实验结果表明,氢钨青铜沉积时间及催化剂沉积顺序对电极催化性能有显著影响,当氢钨青铜沉积时间为10 min,先沉积氢钨青铜、后沉积铂所得Pt/HxWO3电极对氢氧化具有最佳的催化活性。适量的氢钨青铜才能与铂形成较好的协同催化效应。     

Highly efficient mesoporous WO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>/KIT-6 catalysts for oxidative desulfurization of dibenzothiophene with hydrogen peroxide

Oxidative desulfurization (ODS) of organic compounds containing sulfur element from a model oil was performed using tungsten oxide catalysts supported on mesoporous silica with cubic Ia3d mesostructure, well-defined mesopores (7.2 nm), high surface area (719 m²/g), and three-dimensional pore network (WO _x /KIT-6). The prepared WO _x /KIT-6 catalysts (5–20 wt% WO _x ) were characterized by X-ray diffraction analysis, N₂ sorption measurements, electron microscopy, H₂-temperature programmed reduction, Raman spectroscopy, and thermogravimetric analysis. Among the mesoporous catalysts, 10 wt% WO _x /KIT-6 exhibited the best catalytic performance. Sulfur-containing organic compounds, such as dibenzothiophene, 4,6-dimethyldibenzothiophene, and benzothiophene, were completely (100 %) removed from the model oil over 10 wt% WO _x /KIT-6 catalyst in 2 h. In addition, the catalyst could be reused several times with only slight decrease in catalytic activity.     

Electrocatalysis of Water Oxidation by H2O‐Capped Iridium‐Oxide Nanoparticles Electrodeposited on Spectroscopic Graphite

Electrocatalysis of water oxidation by 1.54 nm IrO_x nanoparticles (NPs) immobilized on spectroscopic graphite electrodes was demonstrated to proceed with a higher efficiency than on all other, hitherto reported, electrode supports. IrO_x NPs were electrodeposited on the graphite surface, and their electrocatalytic activity for water oxidation was correlated with the surface concentrations of different redox states of IrO_x as a function of the deposition time and potential. Under optimal conditions, the overpotential of the reaction was reduced to 0.21 V and the electrocatalytic current density was 43 mA cm^?2 at 1 V versus Ag/AgCl (3 M KCl) and pH 7. These results beneficially compete with previously reported electrocatalytic oxidations of water by IrO_x NPs electrodeposited onto glassy carbon and indium tin oxide electrodes and provide the basis for the further development of efficient IrO_x NP‐based electrocatalysts immobilized on high‐surface‐area carbon electrode materials.     

Carbon‐Coated and Interfacial‐Functionalized Mixed‐Phase MoxTi1−xO2‐δ Nanotubes as Highly Active and Durable PtRu Catalyst Support for Methanol Electrooxidation

A synchronous carbon‐coating and interfacial‐functionalizing approach is proposed for the fabrication of Mo‐doped Mo_xTi_1?xO_2‐δ nanotubes (C@IF‐MTNTs) under mild hydrothermal reaction with subsequent annealing as advanced catalyst supports for PtRu nanoparticles (NPs) towards methanol electrooxidation. The carbonation of glucose and Mo‐doping takes place simultaneously at the interface of pristine anatase TiO₂ nanotubes (TNTs), generating a unique concentric multilayered one‐dimensional (1D) structure with crystalline an anatase/rutile mixed‐phase TiO₂ core and Mo‐functionalized interface and subsequently a carbon shell. The obtained PtRu/C@IF‐MTNTs catalyst exhibits an over 2 times higher mass activity with comparable durability than that of the unmodified PtRu/C@TNTs catalyst and over 1.7 times higher mass activity with over 20 % higher stability than that of PtRu/C catalyst. Such superior catalytic performance towards methanol electrooxidation is ascribed to the Mo‐functionalized interface, concentric multilayered 1D architecture, and anatase/rutile mixed‐phase core, which facilitates the charge transport through 1D structural support and electronic interaction between C@IF‐MTNTs and ultrafine PtRu NPs. This work reveals the critical application of a 1D interfacial functionalized architecture for advanced energy storage and conversion.     

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.     

Probing the Catalytic Activity of Reduced Graphene Oxide Decorated with Au Nanoparticles Triggered by Visible Light

Hybrid materials in which reduced graphene oxide (rGO) is decorated with Au nanoparticles (rGO–Au NPs) were obtained by the in situ reduction of GO and AuCl₄^?_(aq) by ascorbic acid. On laser excitation, rGO could be oxidized as a result of the surface plasmon resonance (SPR) excitation in the Au NPs, which generates activated O₂ through the transfer of SPR‐excited hot electrons to O₂ molecules adsorbed from air. The SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB) was then employed as a model reaction to probe the effect of rGO as a support for Au NPs on their SPR‐mediated catalytic activities. The increased conversion of PATP to DMAB relative to individual Au NPs indicated that charge‐transfer processes from rGO to Au took place and contributed to improved SPR‐mediated activity. Since the transfer of electrons from Au to adsorbed O₂ molecules is the crucial step for PATP oxidation, in addition to the SPR‐excited hot electrons of Au NPs, the transfer of electrons from rGO to Au contributed to increasing the electron density of Au above the Fermi level and thus the Au‐to‐O₂ charge‐transfer process.     

Method for Visible Light‐Induced Photocatalytic Degradation of Methylparaben in Water Using Nanostructured Ag/AgBr@m‐WO3

An efficient method of photocatalytic degradation of methylparaben in water using Ag nanoparticles (NPs) loaded AgBr‐mesoporous‐WO₃ composite photocatalyst (Ag/AgBr@m‐WO₃), under visible light is presented. In this process, quantification of methylparaben in water was carried out by high‐performance liquid chromatography (HPLC) and the HPLC results showed a significant reduction of methylparaben in water due to the enhanced of photocatalytic degradation efficiency of Ag/AgBr@m‐WO₃. For the material synthesis, highly ordered mesoporous‐WO₃ (m‐WO₃) was initially synthesized by sol–gel method and AgBr nanoparticles (NPs) were subsequently introduced in the pores of m‐WO₃, and finally, the Ag nanoparticles were introduced by light irradiation. The enhanced photocatalytic degradation of methylparaben in water is attributed to the formation of surface plasmonic resonance (SPR) due to the introduction of Ag NPs on the surface of the catalyst. Also, the formation of heterojunction between AgBr and mesoporous‐WO₃ in Ag/AgBr@m‐WO₃ significantly inhibited the recombination of light‐induced electron‐hole pairs in the semiconductor composite. The morphological and optical characterizations of the synthesized photocatalysts (Ag/AgBr@m‐WO₃) were carried out using SEM, TEM, XDR, N₂ adsorption–desorption, UV‐VIS diffuse reflectance spectroscopy (DRS). Also, the photocatalytic studies using radical scavengers were carried out and the results indicated that ${\text{O}}_2^{·-}$ is the main reactive species.