Theoretical\nInvestigation of Single‑, Double‑,\nand Triple- <i>p</i>‑block Metals Anchored on g‑CN\nMonolayer for Oxygen Electrocatalysis

The design and development of highly active non-noble\nmetal electrocatalysts\nfor the oxygen evolution reaction (OER) and oxygen reduction reaction\n(ORR) are crucial for metal-air batteries. In this work, the electrocatalytic\nperformance of different <i>p</i>-block metal (PM = Sn,\nSb, Pb and Bi) atoms embedded in the g-CN monolayer (PM<sub><i>x</i></sub>@g-CN, <i>x</i> = 1–3) for the OER\nand ORR was systematically investigated by density functional theory\n(DFT). The strong interaction between PM<sub><i>x</i></sub> atoms and g-CN substrates indicates the good stability of PM<sub><i>x</i></sub>@g-CN catalysts. Among all the designed catalysts,\nBi<sub>3</sub>@g-CN is found to be a promising bifunctional electrocatalyst\nfor both the OER and ORR with the calculated overpotential η<sup>OER</sup> and η<sup>ORR</sup> of 0.23 and 0.25 V, respectively.\nWith the atomic active sites of PM<sub><i>x</i></sub> increasing\nfrom <i>x</i> = 1 to 3, the OER and ORR catalytic activity\nis enhanced. The correlations between the overpotentials of the OER/ORR\nand Bader charge values of the anchored PM<sub><i>x</i></sub> atoms of the catalysts were established. Our findings contribute\nto searching for noble metal-free bifunctional electrocatalysts and\nshed light on the rational design of atomic active sites on electrocatalysts.