▎ 摘　　要

Exploring and developing efficient and stable bifunctional electrocatalysts for overall water splitting is of great importance to alleviate the serious consumption of fossil energy sources. Herein, nano-constructed iron sulfide loaded on N-doped graphene foam (Fe7S8/NGF) was obtained by hydrothermal process and chemical vapor deposition (CVD) and used as a highly efficient electrocatalyst for HER (hydrogen evolution reaction) and OER (oxygen evolution reaction). The graphene foam with a three-dimensional porous structure not only improves the overall conductivity of the catalyst but also facilitates the in-situ growth of Fe7S8 nanoparticles and exposes more active sites, thereby optimizing mass and electron transfer. Therefore, the synergistic effect of transition metal sulfide and NGF has greatly enhanced its catalytic performance. In 1 M KOH, Fe7S8/NGF bifunctional electrocatalyst has excellent HER (197.8 mV, 10 mA.cm(-2)) and OER (450 mV, 100 mA.cm(-2)) catalytic ability as well as highly stability for long-term operation. Moreover, the Fe7S8/NGF catalyst exhibits excellent ability for overall water splitting, reaching a current density of 100 mA.cm(-2), requires an additional applied voltage of 2.21 V only, and maintains good stability during 12 hours of continuous work.