Ultrathin NiFeS Nanomeshes with Sulfur Vacancy for Electrocatalytic Hydrogen Evolution

Abstract The development of novel transition metal‐based electrocatalysts with high hydrogen evolution reaction (HER) activity is significant. NiFeS shows promising potential for HER because of its suitable electronic configuration. However, the low ratio of accessible active sites hinders its HER performance. Processing NiFeS into ultrathin nanosheets with abundant pores and vacancies can increase the number of active sites and enhance the intrinsic activity of active sites, but, the synthesis is still challenging. Here, we developed a facile two‐step conversion strategy to prepare ultrathin NiFeS nanomeshes with sulfur vacancies (NiFeS 1‐x UNM). The overpotential of NiFeS 1‐x UNM for 10 mA cm −2 was only 81 mV in acid electrolyte, much lower than the counterpart of NiFeS nanosheets (NiFeS NS) without sulfur vacancies (118 mV). Combining the electrochemical characterizations and Density Functional Theory (DFT) calculations, we revealed that the superior performance of NiFeS 1‐x UNM originated from the increased active sites, accelerated electron/mass transfer and improved intrinsic activity.