Effect of Ni–W–S electrocatalysts on the stability and electrochemical properties of photocathodes

Abstract

Silicon-based photocathodes are attractive for photoelectrochemical (PEC) water splitting, yet their deployment is constrained by reliance on precious metal catalysts like platinum (Pt). Here, we introduce a cost-efficient, tungsten-doped nickel sulfide (NiWS) catalyst, photoelectrodeposited onto a TiO₂-passivated silicon substrate. X-ray photoelectron spectroscopy reveals that W incorporation tailors the local electronic environment of Ni and S, facilitating charge redistribution and accelerating interfacial charge transfer kinetics. The engineered NiWS/TiO₂/Si photocathode delivers a high photocurrent density of −30.8 mA cm⁻² at 0 V_RHE, with an onset potential of 0.58 V_RHE, an applied bias photon-to-current efficiency (ABPE) of 4.47%, and a faradaic efficiency of ∼90% for hydrogen evolution in neutral phosphate buffer (pH 6.5). It also demonstrates exceptional durability, retaining stable operation over 1014 hours under continuous illumination. When integrated with a silicon photovoltaic cell in a tandem architecture, the system enables unbiased solar-driven water splitting, delivering a solar-to-hydrogen (STH) efficiency of 4.01% and sustaining performance for 115 hours under AM1.5G conditions. This work positions NiWS as a scalable, earth-abundant alternative to noble metals for long-term PEC hydrogen production.