富氧空位Co3O4纳米线的制备及其电解水性能研究

在室温下利用NaBH₄溶液还原Co₃O₄纳米线获得富含氧空位（V_O）的三维自支撑纳米线阵列用作全水解电催化剂，其中NaBH₄处理10 min的Co₃O₄/NF在碱性介质中对析氧反应（OER）和析氢反应（HER）表现出很高的活性，在10 mA·cm^-2电流密度下分别仅需240和132 mV的过电位。V_O-Co₃O₄/NF同时作为阴极和阳极电催化剂时，在10 mA·cm^-2下电解水槽电压仅为1.63 V，其耐久性可达60 h以上。该工作为富含氧空位结构的过渡金属氧化物双功能电催化剂的制备提供了新的方法和思路。     

电解海水催化剂的设计与改性

电解海水是一种可再生、可持续、低成本且节约淡水资源的氢气生产方案。因此,针对天然海水或盐水电解质的析氢反应（HER）和析氧反应（OER）,设计开发高效、稳定的电催化剂具有良好的应用前景。为了深入了解海水电解所面临的现状和挑战,本文对电催化分解海水催化剂的设计思路与改性方法进行了系统的回顾和总结。首先详细讨论了电解海水中析氢反应、析氧反应、析氯反应的基本原理。随后对最近报道的在海水中能够稳定运行的HER和OER电催化剂进行了汇总和分析。针对阴极催化剂,分别概述了高效贵金属基电催化剂和低成本过渡金属基电催化剂。针对阳极催化剂,主要讨论了取得较大进展的镍基催化剂,随后对镍基之外的其他电催化剂进行对比补充。文章最后对电解海水催化剂目前所面临的挑战和发展方向进行了总结和展望,基于现有分析认为,在未来的研究中需要进一步探索新型电解海水催化剂的种类和结构,开发更高效稳定的阴极和具有更高OER选择性的阳极电催化剂,以满足分解海水电催化剂工业化应用的要求。     

电催化水分解析氧反应研究现状

析氧反应(OER)是电化学能量转换和储存装置(如氢燃料生产,水电解和可充电金属空气电池)中水分解的关键半电池反应。然而在碱性溶液中,OER反应不具有动力学上的优势,一般需要通过使用贵金属来降低过电位,但贵金属催化剂的高成本和稀缺性限制了其使用。因此,开发高效、廉价、地球资源丰富、稳定、低过电位运行的水裂解电催化剂是实现高效、廉价制氢的关键。综述了电催化水分解析氧反应近几年的国内外研究现状,分析了该研究面临的问题,并对该领域未来的发展进行了展望。     

电沉积钴硒化合物及其电解水析氢性能的研究

本文以CoCl·6H₂O、SeO₂为主盐，在铜箔上电沉积CoSe化合物。研究主盐浓度、沉积电势对CoSe化合物电解水析氢性能的影响。扫描电子显微镜测试表明，电沉积的CoSe化合物具有超薄的纳米片形貌；X射线衍射测试表明，CoSe化合物具有立方体硒钴矿结构。CoSe化合物表现出较优的氢析出活性，在电流密度为10m A·cm^-2时，对应的析氢过电势为244m V。     

一步电沉积制备高活性高稳定镍铁合金析氧电催化剂

以镍网为基底,通过一步电沉积方法成功制备出用于碱性水电解的多孔镍铁合金析氧反应(Oxygen Evolution Reaction,OER)电极.镍铁的沉积伴随强烈的析氢,此条件下构筑出的多级孔结构成为电极用于OER反应时液相中传质与气泡释放的适宜传递通道.在析氧反应中,电流密度为10 mA·cm-2时的过电位仅为21...     

电沉积镍铁锰三元纳米片在析氧反应中的性能研究

电解水制氢技术作为当下最有效的制氢技术之一,低成本、高性能的电催化剂是提高电解水效率的理想选择。本文采用了一步电沉积法在泡沫镍上制备镍、铁、锰三元纳米片(NiFeMn)作为析氧反应(OER)电催化剂。当电流密度为20mA·cm^-2时,过电位达到297mV,Tafel斜率达到了143.2mV·dec^-1,经过了12小时的I-T测试后,其电流密度为86mV·cm^-2,表明该材料具有较好的稳定性和活性。NiFeMn纳米片良好的OER性能可能是由于其高的电化学活性表面积,为OER反应提供了更多的活性位点。     

电沉积法制备碱性电解水镍基析氧电极的研究进展

在“碳达峰、碳中和”的目标下，绿氢成为极具前景的清洁能源。碱性电解水制取绿氢技术商业化程度最高，但由于析氧反应(OER)动力学过程缓慢且需要较高的过电位，成为制约电解水电极效率的主要瓶颈。商业电解槽中广泛使用的镍网或泡沫镍电极的OER性能仍有很大提升空间，在其上复合镍基催化功能层，开发新型高活性的析氧电极有利于提高电极效率，降低制氢成本。电沉积技术具有工艺简单、条件温和、利于放大生产自支撑电极的优势，成为工业化生产OER电极的理想工艺之一。本文综述了近年来利用电沉积技术制备的镍基析氧电极并用于碱性电解水的研究进展。采用电沉积技术在镍网或泡沫镍基底上制备镍(氢)氧化物、双金属及多元金属以及非金属掺杂的镍基催化剂作为催化功能层，通过增强催化功能层的电导率及金属间的协同作用、增加活性位点数量、减小扩散路径以及改变表面原子构型等方式提高镍基自支撑电极的OER性能。最后，展望了镍基自支撑电极在电解水领域的应用，同时指出了电沉积法制备电极材料存在的挑战。     

钌基氢析出反应电催化剂的研究进展

钌具有与铂相近的氢析出反应(HER)催化活性,价格约为铂的一半,是一种替代铂的理想金属。研究高效、稳定并且价格低廉的钌基HER电催化剂是实现氢能源社会的有效途径。介绍了HER机理,总结了最近钌基氢析出反应电催化剂的4种设计策略,展望了钌基氢HER电催化剂的机遇和挑战。     

鸡蛋黄热解制备高效双功能电催化剂

廉价高效的可催化氧还原反应（ORR）和析氧反应的双功能电催化剂是实现可再生燃料电池和金属-空气电池等化学电源大规模商业化应用的关键因素。以鸡蛋黄和六水合氯化钴为前驱体,采用简单的一步热解法制备了杂原子掺杂碳材料（HDC）负载Co₂P纳米颗粒双功能电催化剂（Co₂P-HDC）。采用SEM、TEM、XRD以及XPS等表征手段对所得催化剂的微观形貌、晶体结构以及表面元素组成进行了分析表征。运用旋转圆盘电极（RDE）技术考察了Co₂P-HDC在碱性介质中催化ORR和OER的性能。结果表明,Co₂P-HDC催化剂表现出与商品Pt/C催化剂相当的ORR催化活性以及优于Pt/C催化剂的OER催化活性和耐久性,有望应用于金属-空气电池、可再生燃料电池等化学电源中,并为鸡蛋黄的高附加值利用提供新的途径。     

钼钴二元硫化物制备及其电解水性能研究

为提升硫化钼全解水的催化能力,采用一步电沉积的方法在镍钴氧化物（NCO）基底上成功制备了钼钴二元硫化物复合电极,研究了添加剂、钼钴物质的量比和沉积时间对电极电催化性能的影响。实验结果表明,采用氟化铵作为添加剂、钼钴物质的量比为5∶7且沉积时间为750 s时,制备的Mo₅Co₇S_x@NCO-750电极具有最佳电催化活性,其析氢反应（HER）过电位和Tafel斜率分别为115 mV和67 mV/dec,析氧反应（OER）过电位和Tafel斜率分别为259 mV和42 mV/dec,全解水时槽压为1.61 V。复合电极电催化性能的提升一方面得益于钴的引入,在硫化钼中形成了高导电性和高催化活性的异质界面,另一方面材料中还存在丰富的具有优异电催化活性的缺陷位点。     

Trifunctional electrocatalysts based on feather-like NiCoP 3D architecture for hydrogen evolution,oxygen evolution,and urea oxidation reactions

Finding efficient and versatile catalysts that can both produce clean energy H₂ and treat wastewater is an important matter to solve energy shortages and wastewater pollution. Herein, a feather-like NiCoP supported on NF was synthesized via the two-step hydrothermal-phosphorization process. NiCoP/NF requires only overpotentials of 44 and 203 mV to reach 10 mA cm^?2 for HER and OER in 1 M KOH, respectively. Besides, NiCoP/NF requires only 1.13 V (vs RHE) to achieve 10 mA cm^?2 in 1 M KOH containing 0.33 M urea. DFT calculation shows that NiCoP exhibits enhanced DOS in the Fermi level attachment, which promotes charge transfer. Subsequently, the trifunctional NiCoP/NF, for overall water splitting, requires a lower potential of 1.48 V to gain 10 mA cm^?2 in 1 M KOH. For urea electrolysis, NiCoP/NF requires just 1.36 V to drive 10 mA cm^?2 in 1 M KOH with 0.33 M urea. This work provides extraordinary insights into electrolytic hydrogen production and wastewater treatment through simple preparative methods. The performance of the prepared catalyst is at a high level in non-noble metal.     

Fabrication of efficient nanostructured Co3O4-Graphene bifunctional catalysts: Oxygen evolution,hydrogen evolution,and H2O2 sensing

Nanostructured Co₃O₄-graphene hybrid catalysts are fabricated by a one-step vacuum kinetic spray technique from microparticles of Co₃O₄ and graphite powders. The Co₃O₄-graphene hybrid catalysts with various Co₃O₄ contents are studied concerning the oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in 1.0 M KOH, as well as, H₂O₂ sensing in 0.1 M NaOH. We find that increasing graphene content in the hybrid catalysts results in an overall improvement of the OER electrocatalytic activity due to the enhancement in the charge transfer kinetics. The hybrid catalyst with 25 wt% Co₃O₄ reveals the optimum electrocatalytic activity toward the OER with the lowest overpotential (η) of 283 mV@ 10 mA cm⁻² and superior reaction kinetics with a low Tafel slope of 25 mV dec⁻¹. Besides, the OER stability at 50 mA cm⁻² for 50 h in 1.0 M KOH was verified. The hybrid catalyst with 50 wt% Co₃O₄ revealed the highest activity toward the HER with η of 108 mV@ 10 mA cm⁻², Tafel slope of 90 mV.dec⁻¹, and stability at 50 mA cm⁻² for nearly 30 h. Moreover, it reveals ultrahigh H₂O₂ amperometric detection with superior sensitivity of 18,110 μA mM⁻¹ cm⁻², linear detection range from 20 μM to 1 mM, and a limit of detection of 0.14 μM.     

Layered double hydroxide-based core-shell nanoarrays for efficient electrochemical water splitting

Electrochemical water splitting is an efficient and clean strategy to produce sustainable energy productions (especially hydrogen) from earth-abundant water. Recently, layered double hydroxide (LDH)-based materials have gained increasing attentions as promising electrocatalysts for water splitting. Designing LDHs into hierarchical architectures (e.g., core-shell nanoarrays) is one of the most promising strategies to improve their electrocatalytic performances, owing to the abundant exposure of active sites. This review mainly focuses on recent progress on the synthesis of hierarchical LDH-based core-shell nanoarrays as high performance electrocatalysts for electrochemical water splitting. By classifying different nanostructured materials combined with LDHs, a number of LDH-based core-shell nanoarrays have been developed and their synthesis strategies, structural characters and electrochemical performances are rationally described. Moreover, further developments and challenges in developing promising electrocatalysts based on hierarchical nanostructured LDHs are covered from the viewpoint of fundamental research and practical applications.     

New NiFe2−xCrxO4 spinel films for O2 evolution in alkaline solutions

Spinel-type ternary ferrites with composition NiFe_2−xCr_xO₄ (0 ≤ x ≤ 1) were synthesized by a precipitation method and their physicochemical and electrocatalytic properties have been investigated using IR, XRD, BET surface area, XPS, impedance and Tafel polarization techniques. The study indicated that substitution of Cr from 0.2 to 1.0 mol in the spinel matrix increased the apparent electrocatalytic activity of the base oxide towards the O₂ evolution reaction in 1 M KOH at 25 °C. The apparent electrocatalytic activity of the oxide with 0.8-1.0 mol Cr was found to be the greatest among the present series of oxides investigated. It is noteworthy that the electrocatalytic activity of the oxide with x = 0.8-1.0 was also greater than those of other spinel/perovskite O₂ evolving electrocatalysts reported in literature.     

Influence of magnetic field on hydrogen reduction and co-reduction in the Cu/CuSO4 system

The effects of an applied magnetic field of up to 5 T on hydrogen evolution and cathodic overpotential were studied for H₂SO₄ and an acidic Cu/CuSO₄ system. Cyclic voltammetry, potentiostatic and galvanostatic deposition as well as electrochemical noise measurements were used. The magnetic field simultaneously increases the rate of hydrogen evolution and modifies the hydrogen bubble size. The periodicity of bubble release from a microelectrode is strongly influenced by the field, which may change the characteristic frequency or make it aperiodic, depending on the field orientation relative to buoyancy. The magnetic field stabilizes a bubble growing on a microelectrode, especially at high current densities. For example, bubble volume increases by a factor four in 1.5 T when the Lorentz force acts downwards. The noise spectra around 1 kHz are characteristic of a coalescence phenomenon. Hydrogen co-reduction with copper was studied by scanning electron microscopy and the current efficiency was measured with a quartz crystal microbalance; at −1.0 V it decreases from 95% to 75% in a field of 1.5 T. Bubble release is no longer periodic, but the noise spectrum has a characteristic shape depending on whether the current density is greater than, equal to or less than the diffusion-limited copper current. The field reduces the roughness of the copper deposit, but the current efficiency can be maximized by controlling the system galvanostatically, which allows a high copper deposition rate at overpotential lower than 0.5 V in the applied field, with smooth deposit quality.     

Is alkali-carbonate reaction just a variant of alkali-silica reaction ACR = ASR?

The mechanism of the alkali-carbonate reaction (ACR) has been recognized as being different from that of the more common alkali-silica reaction (ASR). However, the identification of alkali-silica gel in ACR concrete from Cornwall, Ontario, Canada by Katayama, in 1992 raised the possibility that ASR was at least playing a role in the ACR reaction. The acid insoluble residues of the ACR aggregate from Kingston, along with two other aggregates were analyzed to determine what might be contributing to the reaction. The acid insoluble residue of the ACR Kingston rock contains 96% quartz of high solubility in NaOH. Good correlation was found between the amount of quartz and expansion of concrete prisms indicating that the expansion was due mainly to an alkali-silica reaction. This conclusion is supported by observations, in 2008, by Katayama of gel in thin sections of concrete made with the Kingston aggregate. It is concluded that ACR = ASR.     

Tunable Ni/Fe-Mo carbide catalyst with high activity toward hydrogen evolution reaction

Cost-effective catalysts for hydrogen evolution reaction (HER) are attractive for sustainable production of H₂ fuel. Herein, a series of tunable Ni/Fe-Mo carbide catalysts have been synthesized via a sol-gel method coupling with a subsequent high temperature carbonization process. The amount of nickel and iron was tuned in the Mo₇/C precursors, accomplishing a favourable performance of noble-metal-free electrocatalysts for HER. As expected, the designed Ni₁₀Fe₄Mo₇/C catalyst displays an enhanced catalytic activity toward hydrogen production with an ultralow overpotential (η₁₀ = 110 mV) and striking kinetics (η_onset = 58 mV, k = 54 mV · dec⁻¹) in the alkaline electrolyte (1 M KOH), which are comparable to those of the commercial 20% Pt/C catalyst. Such excellent performance of Ni₁₀Fe₄Mo₇/C could be attributed to the high intrinsic activities of Ni-based alloys (NiMo₄) and Mo₂C, as well as to the lattice contraction in the Mo₂C unit cell, in accordance with its high electrochemical surface area (~133 m² · g⁻¹) and low charge-transfer resistance (~31.5 Ω) for the associated electrode.     

Electrochemical deposition and characterization of NiFe coatings as electrocatalytic materials for alkaline water electrolysis

In this study, nickel (Cu/Ni), iron (Cu/Fe) and nickel-iron (Cu/NiFe) composite coatings with various chemical compositions were electrochemically deposited on a copper electrode and characterized using cyclic voltammetry (CV), atomic absorption spectroscopy (AAS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques in view of their possible applications as electrocatalytic materials for the hydrogen evolution reaction (HER) in an alkaline medium. The electrocatalytic activity of the coatings for the HER was studied in 1 M KOH solution using cathodic current-potential curves and electrochemical impedance spectroscopy (EIS) techniques. The presence of nickel along with iron increases the electrocatalytic activity of the electrode for the HER when compared to nickel and iron coatings individually. The HER activity of the composite coatings depends on the chemical composition of the alloys. The Cu/NiFe-3 electrode (with a molar concentration ratio of Ni²⁺:Fe²⁺ of 4:6 in the plating bath) was found to be the best suitable cathode material for the HER in an alkaline medium under the experimental conditions studied. Furthermore, the electrocatalytic activity of the Cu/NiFe-3 electrode for the HER was tested for extended periods of time in order to evaluate the change in the electrocatalytic activity of the electrode with operation time. The HER was activation controlled and has not been changed after electrolysis. A constant current density of 100 mA cm⁻² was applied to the electrolysis system, and the corrosion behavior of the Cu/NiFe-3 electrode was investigated after different operation times using EIS and linear polarization resistance (LPR) techniques. For comparison, the corrosion behavior of a Cu/NiFe-3 electrode to which current was not applied was also investigated. The corrosion tests showed that the corrosion resistance of the Cu/NiFe-3 cathode changed when a cathodic current was applied to the electrolysis system.     

快速界面法制备FeOOH@CoNi-LDH@NF用于高效析氧

以六水合硝酸钴、六水合硝酸镍、尿素和氟化铵为原料,采用水热法在镍网上原位构筑层状双金属氢氧化物(LDH)(CoNi-LDH@NF),然后采用快速界面法在硝酸钠和六水合氯化铁的100℃溶液中对其进行刻蚀制备了FeOOH@CoNi-LDH@NF.利用XRD、SEM、XPS和TEM对FeOOH@CoNi-LDH@NF进行了形...     

Alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali-aggregate reaction in concrete (II) expansion and microstructure of concrete microbar

The effect of the type of alkalis on the expansion behavior of concrete microbars containing typical aggregate with alkali-silica reactivity and alkali-carbonate reactivity was studied. The results verified that: (1) at the same molar concentration, sodium has the strongest contribution to expansion due to both ASR and ACR, followed by potassium and lithium; (2) sufficient LiOH can completely suppress expansion due to ASR whereas it can induce expansion due to ACR. It is possible to use the duplex effect of LiOH on ASR and ACR to clarify the ACR contribution when ASR and ACR may coexist. It has been shown that a small amount of dolomite in the fine-grained siliceous Spratt limestone, which has always been used as a reference aggregate for high alkali-silica reactivity, might dedolomitize in alkaline environment and contribute to the expansion. That is to say, Spratt limestone may exhibit both alkali-silica and alkali-carbonate reactivity, although alkali-silica reactivity is predominant. Microstructural study suggested that the mechanism in which lithium controls ASR expansion is mainly due to the favorable formation of lithium-containing less-expansive product around aggregate particles and the protection of the reactive aggregate from further attack by alkalis by the lithium-containing product layer.