Theoretical Investigation of Single-, Double-, and Triple- <i>p</i>-block Metals Anchored on g-CN Monolayer for Oxygen Electrocatalysis

The design and development of highly active non-noble metal electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are crucial for metal-air batteries. In this work, the electrocatalytic performance of different <i>p</i>-block metal (PM = Sn, Sb, Pb and Bi) atoms embedded in the g-CN monolayer (PM_<i>x</i>@g-CN, <i>x</i> = 1-3) for the OER and ORR was systematically investigated by density functional theory (DFT). The strong interaction between PM_<i>x</i> atoms and g-CN substrates indicates the good stability of PM_<i>x</i>@g-CN catalysts. Among all the designed catalysts, Bi₃@g-CN is found to be a promising bifunctional electrocatalyst for both the OER and ORR with the calculated overpotential η^OER and η^ORR of 0.23 and 0.25 V, respectively. With the atomic active sites of PM_<i>x</i> increasing from <i>x</i> = 1 to 3, the OER and ORR catalytic activity is enhanced. The correlations between the overpotentials of the OER/ORR and Bader charge values of the anchored PM_<i>x</i> atoms of the catalysts were established. Our findings contribute to searching for noble metal-free bifunctional electrocatalysts and shed light on the rational design of atomic active sites on electrocatalysts.