镍硫析氢活性阴极的电化学制备及其电催化机理

以硫代硫酸钠作为硫源, 在基本的瓦特浴镀液体系中通过恒电流电沉积方法获得了不同晶体结构的镍硫合金活性阴极. 通过能量散射谱(EDS)、X射线衍射(XRD)以及扫描电子显微镜(SEM)对镀层的化学成分、晶体结构以及表面形貌进行了分析, 并对活性阴极的电催化活性以及析氢过程机理进行了研究. XRD测试结果表明, 随着镀层中硫含量的变化, 镀层的晶体结构呈现出非晶态/Ni3S2混晶和金属间化合物(Ni3S2)两种晶体结构, 其中, 硫含量为33.9%(原子分数)的非晶态/Ni3S2混晶结构的活性阴极在碱性溶液中具有很好的析氢活性, 其优良的析氢活性主要来自于Ni3S2很强的吸附氢能力. 交流阻抗的测试结果表明, Ni3S2金属间化合物的析氢过程只存在一个电化学反应步骤, 而非晶态/Ni3S2混晶镍硫合金活性阴极的析氢过程存在三个电化学反应步骤.

Electrochemical Preparation and Electrocatalytic Mechanisms of Ni-S Active Cathode for Hydrogen Evolution

Nickel-sulfur electrodes with different crystallographic structures were obtained by galvanostatic electrodeposition froma typical Watts bath containing sodiumthiosulfate as a sulfur source. The chemical composition, crystalline structures, and surface morphologies of deposited films were determined by energy dispersion spectrum (EDS), X-ray diffraction (XRD) pattern, and scanning electron microscope (SEM) analyses. The electrocatalytic activities of the electrodes for hydrogen evolution reaction were studied in detail. The XRD result shows that the Ni-S active electrodes comprise amorphous/Ni3S2 mixed phase structures and intermetallic compound phase structures (Ni3S2) as the S content in the deposited films is increased. When the S content is 33.9% (atomic fraction) the amorphous/Ni3S2 mixed phase electrodes have a higher catalytic activity for the hydrogen evolution reaction in an alkaline solution because of the strong hydrogen adsorption ability of the Ni3S2 intermetallic compound phase. The alternating current (AC) impedance analysis results indicate that hydrogen evolution from the Ni3S2 intermetallic compound belongs to a one-step electrochemical reaction process and that for the amorphous/Ni3S2 mixed phase structures involves three steps.