▎ 摘　　要

The development of low cost, efficient and stable overall water splitting electrocatalysts is essential for green hydrogen production. In this work, we report a defect-rich MoS2/CoS2 heterostructure supported on in situ formed graphene layers (MoS2/CoS2/C) synthesized via gas-phase sulfidation, which enables bifunctionality towards electrocatalytic oxygen evolution and hydrogen evolution reactions (OER and HER). In alkaline medium, the catalyst exhibited overpotentials of 170 mV and 293 mV for HER and OER, respectively. In an alkaline electrolyzer using MoS2/CoS2/C as both cathode and anode, a cell voltage of 1.68 V was delivered at a current density of 10 mA cm(-2), and remarkable stability maintained during 20 h of chronoamperometry test. Furthermore, the Faraday efficiencies of HER and OER in electrolytic water systems are as high as 97.3% and 94.7%, respectively. The good HER and OER catalytic activity over the MoS2/CoS2/C catalyst could be attributed to the abundance of defects, the strong interaction between MoS2 and CoS2, the large electrochemical surface area, and the excellent electron conductivity. Therefore, this work may provide an effective strategy for future development of overall water splitting catalysts. [GRAPHICS]