Modeling Bifunctional Electrocatalysts Through p-Block Metal Incorporation in Transition Metal Doped N-Graphene for Oxygen Evolution and Reduction Reactions

Abstract

Development of efficient bifunctional electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is essential for renewable energy storage and conversion technologies. While transition metal (TM) co-doped N-doped graphene systems (TM-N-G) are well-known for their electrocatalytic performance, their bifunctional activity for both OER and ORR remains limited and inefficient. In this work, bifunctional electrocatalytic performance of TM-N₆-G systems (TM = Fe, Co, and Ni) is investigated by incorporating p-block metals (PM = Al, Ga, In, Sn, and Bi) into an N₄ cavity, resulting in TM-PM-N₆-G structures. Systematic DFT calculations reveal that among all the system configurations, Co-Ga-N₆-G and Co-Sn-N₆-G emerge as highly efficient bifunctional catalysts. The enhanced catalytic activity of Co centres is attributed to optimal interactions with reaction intermediates, as elucidated by scaling relations, volcano plots, and contour maps. These optimal interactions are explained by changes in electronic structure of catalysts and charge redistribution at the TM sites, induced by incorporated PMs. A new descriptor ϒ is proposed to describe the catalytic activity, performing better than conventional d-band center. Additionally, several unifunctional catalysts are identified. This detailed analysis provides key insights and design strategies for developing high-performance bifunctional catalysts via PM doping in TM-N-G systems.