Neutral-Alkaline Hybrid Water Electrolysis at Less Than 1.43 V Enabled by a Branched NiCo-Hydroxysulfide Nanoarray

In this study, a branched and amorphous NiCo-hydroxysulfide nanoarray uniformly coated on a carbon fiber cloth (NiCo-CHS NW/CC) is reported to serve as a Janus and efficient catalyst for alkaline overall water splitting with a low cell voltage of 1.64 V at 10 mA cm–2. The high activity of this catalyst can be attributed to the facilitated electrolyte penetration, promoted gas release, shortened ionic diffusion length, and abundant catalytic active sites enabled by a unique structure with a shaggy surface and an open space as well as the intrinsic high catalytic activity of NiCo-hydroxysulfide. Considering that neutral hydrogen evolution reaction (HER) is more thermodynamically favorable than alkaline HER due to the pH effect, a concept of neutral-alkaline hybrid water splitting enabled by the bifunctional NiCo-CHS NW/CC is further proposed. This hybrid water splitting system exhibits a much lower cell voltage (just 1.43 V at 10 mA cm–2) with a large energy-consumption decrease compared to the alkaline water splitting system.