Nickel sulfide cocatalyst-modified silicon nanowire arrays for efficient seawater-based hydrogen generation†

Abstract

Silicon nanowire arrays (SiNWs) have shown considerable potential as water splitting materials because of their excellent light absorption ability and high surface area-to-volume ratio, which promote photoelectrochemical reactions. However, the catalytic activity of SiNWs for hydrogen evolution is hindered by the slow charge transfer kinetics. Herein, we propose a new approach to boost hydrogen production in simulated seawater employing NiS_x cocatalyst-decorated SiNWs photocathodes. The integration of NiS_x cocatalyst onto SiNWs considerably improves the catalytic performance, enabling efficient hydrogen evolution under simulated sunlight irradiation. The HER performance of NiS_x/SiNWs photocathodes was systematically investigated in simulated seawater. The optimized photocathode exhibited an onset potential of 0.068 V vs. RHE while the SiNWs photocathode showed an onset potential at −0.597 V vs. RHE. Moreover, a remarkable hydrogen evolution rate of 189.15 μmol h⁻¹ cm⁻² was obtained, which is 30.86 times higher than that of pristine SiNWs. Systematic experimental investigations confirmed that the in situ grown nickel sulfide (NiS_x) provides abundant active sites for HER with enhanced photoelectrochemical activity. Furthermore, a stable interface was constructed between SiNWs and NiS_x, which acts as an efficient transport channel of photoelectrons, simultaneously enabling the NiS_x/SiNWs heterostructure with good stability against the alkaline electrolyte-induced deactivation process of the silicon surface. These noteworthy advancements considerably elevate the HER performance of the photocathode. Our findings underscore the potential of this hybrid photocathode system for sustainable hydrogen production from abundant seawater resources.