Di-defects synergy boost electrocatalysis hydrogen evolution over two-dimensional heterojunctions

Electronic modulation on the inert basal plane of transition-metal dichalcogenides(TMDs) through vacancy defect excitation, although extremely challenging, is urgent for understanding the factors that impact the hydrogen evolution reaction (HER) catalytic activity. Here, ultrathin WS2 nanosheets with precise quantitative single atomic S-vacancy on the inert basal plane were flexible prepared through hydrogen peroxide etching strategy. The as-synthesized single atomic S-vacancy defect WS2 (SVD-WS2) nanoflake with the activated basal plane exhibited an impressive overpotential of 137 mV at a current density of 10 mA·cm−2 and a Tafel slope of 53.9 mV·dec−1. Furthermore, anchoring on the defect graphene matrix, the assembled two-dimensional (2D) stacking heterojunction exhibits further enhanced HER catalytic activity (an overpotential of 108 mV vs. 10 mA·cm−2 and a Tafel slope of 48.3 mV·dec−1) and stability (∼ 10% decline after 9,000 cycles), which attributed to the electronic structure modulation from the synergetic interactions between SVD-WS2 and defect graphene. Our finding provides a smart defects introduce strategy to trigger high-efficiency hydrogen evolution over WS2 nanosheets and a general 2D heterojunctions fabricated inspiration based on strong interaction interface.