Plasma tailoring in WTe₂ nanosheets for efficiently boosting hydrogen evolution reaction

2D transition metal dichalcogenides (TMDs) have been considered as promising non-precious electrocatalysts for the hydrogen evolution reaction (HER). However, their limited active sites and poor electric conductivity pose a significant hurdle to their HER performance, resulting in a large overpotential. Here, we report the defect engineering in ultrathin tungsten telluride (WTe₂) nanosheets with semimetal nature to improve hydrogen evolution effectively. We find that the oxygen plasma etching imposes a cutting effect on WTe₂ nanosheets, resulting in a large number of tungsten vacancies. Particularly, the sample after plasma treatment for 10 min shows a feather-like structure with an overpotential of 251 mV at 10 mA/cm² and a Tafel slope of 94 mV/dec, which is 4 times lower than the Tafel slope of pristine nanosheets. Further first-principles calculations shed light on the evolution of defect-rich WTe₂ nanosheets and offer rational explanation to their superiority in efficient hydrogen evolution.