Copper dopants improved the hydrogen evolution activity of earth-abundant cobalt pyrite catalysts by activating the electrocatalytically inert sulfur sites

Abstract

Cobalt pyrite (CoS₂) is considered to be a promising catalyst for the hydrogen evolution reaction (HER) due to its intrinsic metallicity and high catalytic activity. However, the catalytically inert S-sites and sluggish reaction kinetics severely impede its commercial application. Herein, combining systematic theoretical and experimental approaches, a highly active and stable Cu doped CoS₂ catalyst for the HER is demonstrated. Cu dopants are proven to not only reduce the hydrogen adsorption free energy (ΔG_H*) of the Co sites from 0.41 eV to −0.13 eV, but also arouse the inert S sites with the low ΔG_H* of −0.11 eV. A large cathode current density (10 mA cm⁻² at 52 mV), low Tafel slope (42 mV dec⁻¹), large exchange current density (0.68 mA cm⁻²), and good stability were observed in the Co_0.93Cu_0.07S₂ catalyst, which are better than those found for the previously reported CoS₂-based catalysts. The success of improving the electrochemical performance via the introduction of Cu dopants offers new opportunities in the development of high performance CoS₂-based electrodes for other energy-related applications.