Facet engineering of NiCo2S4 electrocatalysts for enhanced hydrogen evolution reaction

Crystal facet engineering is considered to be a powerful method to maximize the inherent catalytic properties of electrocatalysts. In this research, polyvinylpyrrolidone (PVP) served as a surfactant to realize the controllable synthesis of sub-microspheres NiCo2S4 with a highly exposed (400) crystal facet. The sub-microspheres NiCo2S4 (P-0.2) shows excellent catalytic activities as a cathode toward hydrogen evolution reaction (HER) with a lower overpotential of 235 mV at 10 mA·cm−2 in alkaline electrolyte. Moreover, the sub-microspheres NiCo2S4 presents satisfactory durability in the alkaline solution for 24 h. Such remarkable HER performance of electrocatalyst is benefited from the unique sub-microspheres structure, which could highly expose specific crystal facets to provide abundant active sites, and thus enhance the mass/electron transfer efficiency. Furthermore, the increased exposure of (400) facet of NiCo2S4 crystal will offer more S2- during HER, it can effectively stabilize the reaction intermediates.