Phosphorus-doped cobalt sulphide nanocubes as an electrocatalyst for the hydrogen evolution reaction in an alkaline medium

Abstract

Green hydrogen, a zero-carbon-emission fuel, is a promising solution for meeting the energy needs of a sustainable future. Among various production methods, electrochemical water splitting stands out as a superior approach due to its ability to efficiently produce high-purity hydrogen and its potential to be coupled to renewable energy sources. Designing low-cost, highly efficient and durable electrocatalysts for the hydrogen evolution reaction (HER) in alkaline environments is essential for advancing hydrogen production. We have synthesized a cobalt disulfide (CoS₂) nanocube morphology by a simple one step hydrothermal method. However, the HER performance is limited by low conductivity and weak intrinsic catalytic activity. Doping phosphorus into CoS₂ nanocubes introduces P atoms into the P–Co–S structure, which act as active sites, enhancing electrical conductivity and creating additional sites for hydrogen adsorption. This morphology modification facilitates faster electron transfer, resulting in significantly improved catalytic activity for the HER. Notably, P-doped CoS₂ nanocubes demonstrated excellent performance, achieving an overpotential of 138 mV observed at a current density of 10 mA cm⁻² with the determined Tafel slope being 96.2 mV dec⁻¹. Phosphorus-doped CoS₂ exhibited significantly higher current density and enhanced long-term stability in an alkaline medium compared to pristine CoS₂. This work focuses on the development of noble metal-free electrocatalysts for alkaline electrolyzers, aiming to advance the production of green hydrogen energy.