Controllable interfacial electron transfer induced by heterointerfaced sulfur-based catalysts with less electronegative anions for boosted hydrogen evolution reaction in the universal pH range

Abstract

Economic cobalt-sulfide (Co_xS_y)-based electrocatalysts play a vital role in the hydrogen evolution reaction (HER) due to their adjustable electronic structure and environmental friendliness. However, the limited active sites, poor structural stability and intense hydrogen (H) adsorption energy of these catalysts endow them with unsatisfactory performance, which significantly impedes their practical application in acidic/alkaline/neutral media. Herein, we designed a series of defective nickel–cobalt sulfur-based catalysts with an enriched heterogeneous interface. The P anions not only offer ample sulfur defects for charge movement, but also provide a protection layer to prevent structural collapse in acidic/alkaline media. More importantly, the P element with low electronegativity slightly lowers the robust strength of S–H bonds, yet maintains the activity of the S-based catalysts, thereby balancing the adsorption/release of H. Subsequently, the introduction of the heterointerface accompanied by P creates controllable interfacial electron transfer between Ni-based components (Ni₃S_xP_y) and Co components (Co₃S_xP_y), which can regulate the charge state and enhance charge transfer kinetics for boosted HER. Meanwhile, the planar structure establishes a highly conductive network for facilitated ion/electron transportation, leading to an accelerated redox reaction. Attributed to its structural benefits, an admirable HER performance with an optimum overpotential of 56 mV and a Tafel slope of 74 mV dec⁻¹ with −10 mA cm⁻² in 1 M KOH and decent long-term stability can be achieved. This work paves the way for S-based catalyst design to achieve superior HER performance in the universal pH range.