In-situ activation induced surface reconstruction on Cr-incorporated Ni3S2 for enhanced alkaline hydrogen evolution reaction

Ni3S2 has emerged as one of the most promising hydrogen evolution reaction (HER) catalysts due to its moderate activity, exceptional electrical conductivity, and scalable synthesis methods. However, the high energy barrier for H2O dissociation and weak desorption of the H* intermediate severely hinder its HER kinetics. In this study, a novel Cr-incorporated Ni3S2 was grown on a Ni mesh substrate (denoted as Cr-Ni3S2/NM) using a one-step electrodeposition approach, resulting in a large surface area with abundant Ni3S2/Cr2S3 heterojunctions. Subsequently, it underwent surface reconstruction after in situ activation (denoted as A-Cr-Ni3S2/NM), which not only enhanced charge and mass transfer but also altered the electronic structure by introducing more oxygen species on the catalyst surface and creating S vacancies. Using theoretical calculations, this in situ activation was shown to not only promote charge transport but also boost HER kinetics by strengthening OH* desorption for H2O dissociation and facilitating the desorption of H* intermediates. As a result, the fabricated A-Cr-Ni3S2/NM demonstrated exceptional HER performance with a small overpotential of 78 mV to deliver a current density of -10 mA cm-2, along with stability for over 200 h at 100 mA cm-2. While surface reconstruction has been intensively studied in catalysts for the oxygen evolution reaction, we illustrate that it also plays a significant and positive role in Cr-Ni3S2 HER catalysts in this study, thus providing a pathway for achieving high-performance HER catalysts.