Computational screening of Group VⅢ@C5N4 single-atom electrocatalysts for overall water splitting

Single-atom catalysts (SACs) have great potential for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) since their high atomic utilization and strong metal–support interactions. Herein, we develop TM@C₅N₄ (TM = Fe, Co, Ni, Ru, Rh, Pd, Os, Ir and Pt) catalysts via embedding Group VⅢ TM in holey C₅N₄ substrate and further evaluate their electrocatalytic activity using density functional theory (DFT) calculations. Systematical studies indicate that Fe@C₅N₄, Pd@C₅N₄ and Ir@C₅N₄ catalysts all exhibit excellent HER performance, which mainly because of their small ΔG_H* values of 0.101 eV, -0.114 eV and 0.070 eV, respectively. In parallel, Rh@C₅N₄ and Ir@C₅N₄ possess high OER activity along with low overpotential of 0.50 V, which is superior to the commercial IrO₂ catalyst (0.56 V). Obviously, Ir@C₅N₄ could be utilized as bifunctional electrocatalysts both HER and OER in water splitting. Furthermore, we analyze their correlative catalytic mechanisms using the molecular orbitals. Besides, biaxial strain modulation could effectively regulate the catalytic activity of HER and OER. Particularly, 2 % biaxial tensile strain could bring Ir@C₅N₄ superb HER/OER catalytic performance. Finally, we anticipate that this strain engineering would provide a new perspective for developing high-performance SACs for water splitting.