Sulfur-vacancy rich nonstoichiometric TiS2−x/NiS heterostructures for superior universal hydrogen evolution

Abstract

Water electrolysis has been recognized as one of the most promising approaches to produce green hydrogen and eventually target carbon neutrality. Various cost-effective and light transition metal sulfides have been developed as the electrocatalysts to promote hydrogen evolution reaction (HER), one half-reaction of water electrolysis. Unfortunately, full use of their intrinsic electrocatalytic traits and exposed active sites is still challenging. Here, a nonstoichiometric titanium sulfide/nickel sulfide (TiS2−x/NiS) hetero-catalyst is designed and constructed to induce a high-density of sulfur vacancies. As a HER electrocatalyst, it features the overpotentials of only 63 and 134 mV at a current density of 10 mA cm−2 in 1.0 M KOH and 0.5 M H2SO4, respectively, which is equipped with glorious durability even at high current densities (e.g., 100 mA cm−2 and 500 mA cm−2). Such outstanding performance partially stems from the sulfur vacancies induced by a nonstoichiometric effect, namely the intensified interfacial charge transfer nearby the TiS2−x/NiS heterointerface. The existence of sulfur vacancies partially regulates the d-electronic structure of Ti and Ni active sites, ultimately bringing in reduced energy barrier of water dissociation as well as optimized adsorption free energy for H* intermediates. The strategy of employing both a nonstoichiometric effect and interface engineering of a metal sulfide catalyst paves a new way to design high-performance and cost-effective HER electrocatalyst in universal media.