Electrochemical preparation and electrocatalytic mechanisms of Ni-S active cathode for hydrogen evolution

Abstract

Nickel-sulfur electrodes with different crystallographic structures were obtained by galvanostatic electrodeposition from a typical Watts bath containing sodium thiosulfate 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. © Editorial office of Acta Physico-Chimica Sinica.