双金属催化剂Ni-Co/SiO2空心球的可控制备及催化性能

以二氧化硅为模板, 采用牺牲模板/界面反应法制备具有介孔结构的碱式硅酸镍钴空心球。采用透射电子显微镜(TEM)、X 射线衍射(XRD)、氮气吸脱附曲线(BET)和程序升温还原(TPR)等方法, 对样品的结构和形貌进行了表征, 探索了碱式硅酸镍钴空心球还原规律, 并研究了双金属催化剂Ni-Co/SiO₂的催化性能。研究发现, 140℃下反应6 h, 产物为核壳结构, 反应12 h时变为空心球结构; 在氢气气氛中800℃下反应5 h, 碱式硅酸镍钴被完全还原为Ni-Co/SiO₂, 还原前后形貌基本不变, 但比表面积有所减小, 孔径增大。Ni-Co/SiO₂空心球用于催化硝基苯加氢反应1 h后, 硝基苯的转化率为67%, 比商用Raney Ni 提高约28%。     

Preparation of nanostructured NiFe2O4 catalysts by combustion reaction

Nanosize nickel ferrite powders (NiFe₂O₄) have been prepared by combustion reaction using nitrates and urea as fuel. The resulting powders were characterized by X-ray diffraction (XRD), nitrogen physical adsorption (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and catalytic activity. The results showed nanosize nickel ferrite powders with high specific surface area (55.21 m²/g). The powders showed extensive XRD line broadening and the crystallite size calculated from the XRD line broadening was 18.0 nm. The nickel ferrite powder presented significant activity as catalyst for the water gas shift reaction, over the temperature range of 250–450 °C.     

Hierarchical nano-on-micro copper with enhanced catalytic activity towards electro-oxidation of hydrazine

The electrochemical properties of catalyst materials are highly dependent on the materials structure and architecture. Herein, nano-on-micro Cu electrodes are fabricated by growing Cu microcrystals on Ni foam substrate, followed by introducing Cu nanocrystals onto the surface of the Cu microcrystals. The introduction of Cu nanocrystals onto the surface of Cu microcrystals is shown to dramatically increase the electrochemically active surface area and thus significantly enhances the catalytic activity of the catalyst electrode towards electro-oxidation of hydrazine. The onset potential (-1.04 V vs. Ag/AgCl) of the nano-on-micro Cu electrode is lower than those of the reported Cu-based catalysts under similar testing conditions, and a current density of 16 mA·cm^-2, which is 2 times that of the microsized Cu electrode, is achieved at a potential of -0.95 V vs. Ag/AgCl. Moreover, the nano-on-micro Cu electrode demonstrates good long-term stability.     

Cobalt Iron Hydroxide as a Precious Metal‐Free Bifunctional Electrocatalyst for Efficient Overall Water Splitting

Highly efficient and stable electrocatalysts from inexpensive and earth‐abundant elements are emerging materials in the overall water splitting process. Herein, cobalt iron hydroxide nanosheets are directly deposited on nickel foam by a simple and rapid electrodeposition method. The cobalt iron hydroxide (CoFe/NF) nanosheets not only allow good exposure of the highly active surface area but also facilitate the mass and charge transport capability. As an anode, the CoFe/NF electrocatalyst displays excellent oxygen evolution reaction catalytic activity with an overpotential of 220 mV at a current density of 10 mA cm^?2. As a cathode, it exhibits good performance in the hydrogen evolution reaction with an overpotential of 110 mV, reaching a current density of 10 mA cm^?2. When CoFe/NF electrodes are used as the anode and the cathode for water splitting, a low cell voltage of 1.64 V at 10 mA cm^?2 and excellent stability for 50 h are observed. The present work demonstrates a possible pathway to develop a highly active and durable substitute for noble metal electrocatalysts for overall water splitting.     

The effect of LaFeO3@MnO2 on the thermal behavior of energetic compounds: An efficient catalyst with core-shell structure

Large particle size and low specific surface area are two major factors of restricting metal oxides as combustion catalyst with high performance. The construction of three-dimensional (3D) heterojunction materials with synergistic effect is conducive to enhancing the catalytic activity. In this work, LaFeO₃ were prepared by a facile solvo-thermal method and post-heat treament. However, the LaFeO₃ with a large particle size shows poor specific surface area, resulting in a low catalytic activity. In order to improve its catalytic activity, a 3D core/shell heterostructured LaFeO₃@MnO₂ composite was constructed by coupling LaFeO₃ with MnO₂. The core-shell structured LaFeO₃@MnO₂ provides a larger specific surface area and high catalytic effect on the thermal decomposition of ammonium perchlorate (AP) with a reduced decomposition temperature from 403.73 °C to 281.38 °C, an enhanced energy release from 649.6 J·g⁻¹ to 966.5 J·g⁻¹, and a decreased apparent activation energy from 139.05 kJ·mol⁻¹ to 110.88 kJ·mol⁻¹. Additionally, LaFeO₃@MnO₂ also shows efficient catalytic effects on the thermal decomposition of hexanitrohexaazaisowurzitane (CL-20) and cyclotetramethylenetetranitramine (HMX)_.     

The catalytic oxidation of aromatic hydrocarbons over supported metal oxide

The catalytic activity of metals (Cu, Mn, Fe, V, Mo, Co, Ni, Zn)/gamma-Al2O3 was investigated to bring about the complete oxidation of benzene, toluene and xylene (BTX). Among them, Cu/gamma-Al2O3 was found to be the most promising catalyst based on activity. X-ray diffraction (XRD), Brunauer Emmett Teller method (BET), electron probe X-ray micro analysis (EPMA) and temperature programmed reduction (TPR) by H2 were used to characterize a series of supported copper catalysts. Increasing the calcination temperature resulted in decreasing the specific surface areas of catalysts and, subsequently, the catalytic activity. Copper loadings on gamma-Al2O3 had a great effect on catalytic activity, and 5 wt.% Cu/gamma-Al2O3 catalyst was observed to be the most active, which might be contributed to the well-dispersed copper surface phase. Using TiO2 (anatase), TiO2 (rutile), SiO2 (I) and SiO2 (II) as support instead of gamma-Al2O3, the activity sequence of 5 wt.% Cu with respect to the support was gamma-Al2O3 > TiO2 (rutile) > TiO2 (anatase)>SiO2 (I) > SiO2 (II), and this appeared to be correlated with the distribution of copper on support rather than with the specific surface area of the catalyst. The smaller particle size of copper, due to its high dispersion on support, had a positive effect on catalytic activity. The activity of 5 wt.% Cu/gamma-Al2O3 with respect to the VOC molecule was observed to follow this sequence: toluene > xylene > benzene. Increasing the reactant concentration exerted an inhibiting effect on the catalytic activity.     

Growth of carbon nanotubes on aluminium foil for supercapacitors electrodes

A new approach for the preparation of carbon nanotubes (CNTs) electrode is proposed in the present work. Multi-walled carbon nanotubes (MWCNTs) were grown by chemical vapour deposition on aluminium strips pre-plated with a nickel thin film as the catalyst. The CNTs were characterized by scanning and transmission electron microscopy, Brunauer–Emmett–Teller surface area measurement and thermogravimetric analysis. The nickel-plated aluminium foil with a layer of CNTs was further characterized for an assessment of its electrochemical behaviour as electrode for supercapacitors. The specific capacitances of the electrode, as derived from cyclic voltammetry measurement at 0.1 V s⁻¹ scan rate, was found to be 54 and 79 F g⁻¹ in aqueous and organic electrolytes, respectively, in line with the highest reported values for either activated carbon or MWCNTs electrodes. Further evidence in support of the viability of the present approach for the preparation of a CNTs electrode was obtained from electrochemical impedance spectroscopy.     

On the elemental substitutions of titanium-based hydrogen-storage alloy electrodes for rechargeable Ni–MH batteries

Partial substitutions of nickel in Ti2Ni intermetallic compound with cobalt, potassium, boron and aluminium have been studied in the present paper. It is found that cobalt and boron additions are beneficial but aluminium addition is detrimental to the specific capacity of the electrode. Potassium does not have any significant effect on the specific capacity of the electrode from our work. Cobalt, potassium and aluminium additions are all found effective in increasing the cycle life of Ti2Ni electrode, although by different mechanisms. This revised version was published online in November 2006 with corrections to the Cover Date.     

Estimating surface area of copper powder: A comparison between electrochemical,microscopy and laser diffraction methods

For heterogeneous catalytic/electrocatalytic reaction systems, estimation of the surface area of the catalyst is of great importance. As far as systems involving copper as catalyst are concerned, the literature reveals lack of a robust method to determine the surface area. In this work, we compare the surface area determined from electrochemical measurements, optical and electron microscopy and from laser diffraction experiments. Specifically, cyclic voltammetry in two different solutions involving two separate surface reactions has been used to measure the surface area. First involves the formation of a monolayer of Cu₂O and the second involves formation of a monolayer of Pb. Additionally, the surface area was also estimated from the double layer capacitance of the copper electrode. The surface areas determined from these electrochemical measurements are in good agreement with those obtained from microscopy and particle size analyzers (for average copper particle diameter?=?10?µm).     

Synergistic Nanotubular Copper‐Doped Nickel Catalysts for Hydrogen Evolution Reactions

Developing highly active electrocatalysts with low cost and high efficiency for hydrogen evolution reactions (HERs) is of great significance for industrial water electrolysis. Herein, a 3D hierarchically structured nanotubular copper‐doped nickel catalyst on nickel foam (NF) for HER is reported, denoted as Ni(Cu), via facile electrodeposition and selective electrochemical dealloying. The as‐prepared Ni(Cu)/NF electrode holds superlarge electrochemical active surface area and exhibits Pt‐like electrocatalytic activity for HER, displaying an overpotential of merely 27 mV to achieve a current density of 10 mA cm^?2 and an extremely small Tafel slope of 33.3 mV dec^?1 in 1 m KOH solution. The Ni(Cu)/NF electrode also shows excellent durability and robustness in both continuous and intermittent bulk water electrolysis. Density functional theory calculations suggest that Cu substitution and the formation of NiO on the surface leads to more optimal free energy for hydrogen adsorption. The lattice distortion of Ni caused by Cu substitution, the increased interfacial activity induced by surface oxidation of nanoporous Ni, and numerous active sites at Ni atom offered by the 3D hierarchical porous structure, all contribute to the dramatically enhanced catalytic performance. Benefiting from the facile, scalable preparation method, this highly efficient and robust Ni(Cu)/NF electrocatalyst holds great promise for industrial water–alkali electrolysis.     

镁-镍合金催化剂制备及纳米碳管生长模式研究

采用多元醇法制备镁-镍合金纳米粉末,并以此为催化剂制备纳米碳管,利用比表面和孔径分布测定仪、X射线衍射仪和透射电镜,研究镁-镍合金催化剂的性能和纳米碳管的生长模式。结果表明:Mg∶Ni值对镁-镍合金催化剂特性影响较大,其中Mg∶Ni为1的催化剂颗粒比表面积较大且平均粒径较小;聚乙烯吡咯烷酮(PVP)用量增大,有利于提高催化剂颗粒的比表面积、减小平均粒径,但用量过大不利于Mg2Ni合成。在以镁-镍合金为催化剂制备碳纳米管的过程中,首先在催化剂表面形成碳膜,随后形成的碳膜将前期形成的碳膜及催化剂颗粒向外推挤,催化剂颗粒移动后遗留下中空隧道,最终形成碳管,由于纳米碳管尖端的催化剂颗粒反应后失去催化活性,碳管的生长动力主要来自碳管根部。     

Selective Adsorption Behavior Modulation on Nickel Selenide by Heteroatom Implantation and Heterointerface Construction Achieves Efficient Co-production of H2 and Formate

Glycerol-assisted hybrid water electrolysis is a potential strategy to achieve energy-efficient hydrogen production. However, the design of an efficient catalyst for the specific reaction is still a key challenge, which suffers from the barrier of regulating the adsorption characteristics of distinctive intermediates in different reactions. Herein, a novel rationale that achieves selective adsorption behavior modulation for self-supported nickel selenide electrode by heteroatom implantation and heterointerface construction through electrodeposition is developed, which can realize nichetargeting optimization on hydrogen evolution reaction (HER) and glycerol oxidation reaction (GOR), respectively. Specifically, the prepared Mo-doped Ni₃Se₂ electrode exhibits superior catalytic activity for HER, while the NiSe-Ni₃Se₂ electrode exhibits high Faradaic efficiency (FE) towards formate production for GOR. A two-electrode electrolyzer exhibits superb activity that only needs an ultralow cell voltage of 1.40 V to achieve 40 mA cm⁻² with a high FE (97%) for formate production. Theoretical calculation unravels that the introduction of molybdenum contributes to the deviation of the d-band center of Ni₃Se₂ from the Fermi level, which is conducive to hydrogen desorption. Meanwhile, the construction of the heterojunction induces the distortion of the surface structure of nickel selenide, which exposes highly active nickel sites for glycerol adsorption, thus contributing to the excellent electrocatalytic performance.     

Single Ni Atoms and Clusters Embedded in N‐Doped Carbon “Tubes on Fibers” Matrix with Bifunctional Activity for Water Splitting at High Current Densities

Among the bifunctional catalysts for water splitting, recently emerged transition‐metal single‐atom catalysts are theoretically considered to possess high potential, while the experimental activity is not satisfactory yet. Herein, an exceptionally efficient trifunctional metal–nitrogen–carbon (M–N–C) catalyst electrode, composed of a hierarchical carbon matrix embedding isolated nickel atoms with nickel–iron (NiFe) clusters, is presented. 1D microfibers and nanotubes grow sequentially from 2D nanosheets as sacrificial templates via two stages of solution‐ and solid‐phase reactions to form a 1D hierarchy. Exceptionally efficient bifunctional activity with an overpotential of only 13 mV at 10 mA cm^?2 toward hydrogen evolution reaction (HER) and an overpotential of 210 mV at 30 mA cm^?2 toward oxygen evolution reaction (OER) is obtained, surpassing each monofunctional activity ever reported. More importantly, an overpotential of only 126 and 326 mV is required to drive 500 mA cm^?2 toward the HER and OER, respectively. For the first time, industrial‐scale water splitting with two bifunctional catalyst electrodes with a current density of 500 mA cm^?2 at a potential of 1.71 V is demonstrated. Lastly, trifunctional catalytic activity including oxygen reduction reaction is also proven with a half‐wave potential at 0.848 V.     

Cobalt‐Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage

Compared to single metallic Ni or Co phosphides, bimetallic Ni–Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one‐step solvothermal process is proposed for the synthesis of bouquet‐like cobalt‐doped nickel phosphite (Ni₁₁(HPO₃)₈(OH)₆), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ electrode presents a maximum specific capacitance of 714.8 F g^?1. More significantly, aqueous and solid‐state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm^?2 at the power density of 0.6 KW cm^?2. The solid‐state device shows a high energy density of 14.72 mWh cm^?2 at the power density of 0.6 KW cm^?2. These excellent performances confirm that the cobalt‐doped Ni₁₁(HPO₃)₈(OH)₆ are promising materials for applications in electrochemical energy storage devices.     

Time-dependent growth of CaO nano flowers from egg shells exhibit improved adsorption and catalytic activity

Succulent shaped CaO 3D nano flowers have been synthesized by time growth morphological evaluation from bud-to-blossom using dumped egg shells. A comparative study between commercially available calcium oxide and synthesized CaO nano flowers for adsorptive removal of used engine oil and aldol condensation was conducted. The as-synthesized nano particles were characterized by hydrodynamic particle size analyser, surface area by (BET) Brunauer-Emmett-Teller, XRD (X-ray Diffraction) for crystal structural and SEM-EDX (Scanning Electron Microscopy - Energy Dispersive X-ray) and HR-TEM (High-Resolution-Transmission Electron Microscopy) for morphological examinations. The average size distribution calculated using W-H analysis (1.28–1.38 µm) and morphological studies (1.26–1.30 µm) were in good agreement. The CaO_nsf showed higher adsorption activity for spill oil remediation by dispersion-adsorption method with an extent of separation capacity upto 18 times its weight (18.31 gg⁻¹ of CaO_nsf) in comparison to CaO_cm (8.4 gg⁻¹). The as-synthesized nano flowers displayed excellent catalytic activity for aldol condensation between acetophenone and benzaldehyde. The nano flowers comprising of succulent petals, are formed from many irregular elongated nanospheres. Higher surface area availability leads to higher catalytic activity for production of chalcone with a yield of about 76.3%. This study paves a way for development of CaO based 3D nanostructures, possessing higher adsorption efficiency for oil and an efficient catalyst for base catalysed reactions.     

Efficient Oxygen Evolution and Gas Bubble Release Achieved by a Low Gas Bubble Adhesive Iron–Nickel Vanadate Electrocatalyst

Surface chemistry is a pivotal prerequisite besides catalyst composition toward advanced water electrolysis. Here, an evident enhancement of the oxygen evolution reaction (OER) is demonstrated on a vanadate‐modified iron–nickel catalyst synthesized by a successive ionic layer adsorption and reaction method, which demonstrates ultralow overpotentials of 274 and 310 mV for delivering large current densities of 100 and 400 mA cm^?2, respectively, in 1 m KOH, where vigorous gas bubble evolution occurs. Vanadate modification augments the OER activity by i) increasing the electrochemical surface area and intrinsic activity of the active sites, ii) having an electronic interplay with Fe and Ni catalytic centers, and iii) inducing a high surface wettability and a low‐gas bubble‐adhesion for accelerated mass transport and gas bubble dissipation at large current densities. Ex situ and operando Raman study reveals the structural evolution of β‐NiOOH and γ‐FeOOH phases during the OER through vanadate‐active site synergistic interactions. Operando dynamic specific resistance measurement evidences an accelerated gas bubble dissipation by a significant decrease in the variation of the interfacial resistance during the OER for the vanadate‐modified surface. Achievement of a high catalytic turnover of 0.12 s^?1 suggests metallic oxo‐anion modification as a versatile catalyst design strategy for advanced water oxidation.     

Ternary Porous Cobalt Phosphoselenide Nanosheets: An Efficient Electrocatalyst for Electrocatalytic and Photoelectrochemical Water Splitting

Exploring efficient and earth‐abundant electrocatalysts is of great importance for electrocatalytic and photoelectrochemical hydrogen production. This study demonstrates a novel ternary electrocatalyst of porous cobalt phosphoselenide nanosheets prepared by a combined hydrogenation and phosphation strategy. Benefiting from the enhanced electric conductivity and large surface area, the ternary nanosheets supported on electrochemically exfoliated graphene electrodes exhibit excellent catalytic activity and durability toward hydrogen evolution in alkali, achieving current densities of 10 and 20 mA cm^?2 at overpotentials of 150 and 180 mV, respectively, outperforming those reported for transition metal dichalcogenides and first‐row transition metal pyrites catalysts. Theoretical calculations reveal that the synergistic effects of Se vacancies and subsequent P displacements of Se atoms around the vacancies in the resulting cobalt phosphoselenide favorably change the electronic structure of cobalt selenide, assuring a rapid charge transfer and optimal energy barrier of hydrogen desorption, and thus promoting the proton kinetics. The overall‐water‐splitting with 10 mA cm^?2 at a low voltage of 1.64 V is achieved using the ternary electrode as both the anode and cathode, and the performance surpasses that of the Ir/C–Pt/C couple for sufficiently high overpotentials. Moreover, the integration of ternary nanosheets with macroporous silicon enables highly efficient solar‐driven photoelectrochemical hydrogen production.     

Preparation of mesoporous Co-B catalyst via self-assembled triblock copolymer templates

Mesoporous Co-B with worm-like morphology was firstly prepared via reduction of cobalt acetate by potassium borohydride in the presence of triblock copolymer templates. The as-prepared mesoporous Co-B was characterized by Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma (ICP), X-ray photoelectron spectroscopy (XPS), and N₂ adsorption-desorption. During the hydrolysis of KBH₄, the mesoporous Co-B exhibited much higher catalytic activity than the regular Co-B. It is attributed to the larger specific surface area (163.77 m²/g) and mesoporous channels. The average H₂ generation rate of the mesoporous Co-B was 3523 mL/min g catalyst in 1.3 wt% NaOH + 13 wt.% KBH₄ solution at 286 K, which may give a successive H₂ supply for a 571 W polymer electrolyte membrane fuel cell (PEMFC) at 100% H₂ utilization. Furthermore, the as-prepared mesoporous Co-B with high specific surface area is expected to find applications in many catalytic hydrogenation reactions.     

高活性铜/玻璃纤维催化剂的制备及其性能研究

为了降低亚氨基二乙酸的生产成本,解决催化剂活性低、重复使用效果差的问题,通过电沉积的方法制备出高活性的铜/玻璃纤维催化剂,并对其晶格参数和比表面积等进行了测试,再将其用于催化二乙醇胺氧化脱氢合成亚氨基二乙酸.结果表明,自制的催化剂可使亚氨基二乙酸的转化率达到99.4%,选择性达到98.7%,并可循环使用38次以上.Raney Cu/玻璃纤维催化剂与Raney Cu相比具有高活性、高选择性和使用寿命长的特点,可望成为亚氨基二乙酸工业用催化剂.     

Well‐Defined Cobalt Catalyst with N‐Doped Carbon Layers Enwrapping: The Correlation between Surface Atomic Structure and Electrocatalytic Property

Admittedly, the surface atomic structure of heterogenous catalysts toward the electrochemical oxygen reduction reaction (ORR) are accepted as the important features that can tune catalytic activity and even catalytic pathway. Herein, a surface engineering strategy to controllably synthesize a carbon‐layer‐wrapped cobalt‐catalyst from 2D cobalt‐based metal–organic frameworks is elaborately demonstrated. Combined with synchrotron radiation X‐ray photoelectron spectroscopy, the soft X‐ray absorption near‐edge structure results confirmed that rich covalent interfacial Co? N? C bonds are efficiently formed between cobalt nanoparticles and wrapped carbon‐layers during the polydopamine‐assisted pyrolysis process. The X‐ray absorption fine structure and corresponding extended X‐ray absorption fine structure spectra further reveal that the wrapped cobalt with Co–N coordinations shows distinct surface distortion and atomic environmental change of Co‐based active sites. In contrast to the control sample without coating layers, the 800 °C‐annealed cobalt catalyst with N‐doped carbon layers enwrapping achieves significantly enhanced ORR activity with onset and half‐wave potentials of 0.923 and 0.816 V (vs reversible hydrogen electrode), highlighting the important correlation between surface atomic structure and catalytic property.