Ni3S2/ball-milled silicon flour as a bi-functional electrocatalyst for hydrogen and oxygen evolution reactions

Abstract

Elaborate design of highly efficient and durable electrocatalysts from earth-abundant elements is a milestone in the field of electrochemistry. In this study, heazlewoodite (Ni3S2) was successfully grafted on the silicon flour (Ni3S2@SiF) and ball-milled silicon flour (Ni3S2@B–SiF) through a simple hydrothermal process. The products were then etched using the HF solution to prepare the modified porous silicon (PSi) compounds of Ni3S2@PSi and Ni3S2@B–PSiF. Electrochemical studies showed that Ni3S2@B–SiF and Ni3S2@B–PSiF were not only durable but also exhibited electrocatalytic activity toward both alkaline and acidic hydrogen evolution reactions (HER) with appropriate Tafel slopes of 74 and 52 mV dec−1, respectively. Moreover, they recorded an electrocatalytic activity for the oxygen evolution reaction (OER) with an overpotential of 164 mV dec−1. Based on the electrocatalytic studies, the Ni3S2@B–PSiF electrocatalyst was found to have the best electrocatalytic behavior toward HER and OER. The isolated island architecture of the bi-functional (i.e., HER and OER) electrocatalyst could act as promising electrode materials for water splitting using electrochemical methods.