Holey graphitic carbon nitride (g-CN) supported bifunctional single atom electrocatalysts for highly efficient overall water splitting

Downsizing metal-based catalysts to construct single atom catalysts (SACs) is currently an emerging focus in research community of electrocatalysis, however, encountering the common aggregation of metal sites. Herein, the catalytic performance of holey g-CN supported SACs (Ti, V, Cr, Mn, Fe, Co and Ni) toward hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are evaluated. Co-1/g-CN and Ni-1/g-CN are identified as the most efficient bifunctional single atom catalysts for overall water splitting, capable of driving HER/OER simultaneously with overpotentials being as low as 0.15/0.61 V and 0.12/0.40 V, outperforming the commercial Pt and IrO2. Remarkably, the d band centers of TM atoms can act as an efficient descriptor for the interaction strength between intermediates and TM/g-CN, which can be tuned to further optimize the catalytic activity. This work heralds a new family of bifunctional single atom electrocatalysts for overall water splitting, elucidating a useful guideline for designing advanced SACs.