Efficient hydrogen evolution from degenerate-doped p-type WS2 electrocatalysts over a wide pH range

Layered MoS2 and WS2 semiconductors are well-known electrocatalysts for hydrogen generation by electrochemical water splitting. However, their hydrogen evolution reaction (HER) activity is significantly affected in neutral and alkaline environments due to sluggish kinetics and a slow charge transfer rate. Here, we report the improved electrochemical activity of Ir-doped degenerate WS2 semiconductors under different electrolytic conditions covering a wide pH range. It was found that the pristine WS2 (n-WS2) transforms into p-type semiconductors after Ir-doping, among which the sample with Ir 9.8 at% shows a degenerate (p(+)-WS2-9.8) semiconductor nature with high hole density. The p(+)-WS2-9.8 catalyst exhibits superior HER activity with a low overpotential (eta(10) = 92, 248, and 548 mV vs. RHE) and low Tafel slope (b = 33, 49, and 89 mV dec(-1)) in 0.5 M H2SO4, 1 M KOH, and 1 M Na2SO4 electrolytes, respectively. The hole-degenerate doping-induced enhancement of electrical conductivity enables efficient HER activity of the doped semiconductor catalyst. This work demonstrates that degenerate doping is a potential research strategy for the design and development of 2D semiconductor-based efficient catalysts.