▎ 摘　　要

Developing efficient bi-functional catalysts for simultaneous hydrogen evolution (HER) and oxygen evolution reactions (OER) is a promising yet challenging goal. Using first-principles computations, we proposed a novel design of a nickel single atom catalyst (Ni-SAC) supported by a hybridized graphene-boron nitride monolayer (BCN), to work as a highly active bi-functional electrocatalyst for both HER and OER. B-vacancy defects on BCN can immobilize Ni-SACs with high diffusion barriers. Owing to the effective charge polarization and synergistic effects between graphene, the BN domain, and Ni atoms, this design exhibits remarkable electrocatalytic activity with very low overpotentials of 0.47/0.02 V for OER/HER. Our design not only provides great potential for achieving overall water splitting but also adds a new class of electrocatalysts for a wide range of clean energy technologies.