Effect of Ni-W-S electrocatalysts on the stability and electrochemical properties of photocathode

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 TiO 2 -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/TiO 2 /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 AM 1.5G conditions. This work positions NiWS as a scalable, earth-abundant alternative to noble metals for long-term PEC hydrogen production.