Electrocatalytic performance of Mn-adsorbed g-C3N4: a first-principles study

Abstract

Single-atom catalysts with magnetic elements as the active center have been widely exploited as efficient oxygen evolution reaction (OER) electrocatalysts. Here, different contents of transition metal atom Mn adsorbed on graphitic carbon nitride (g-C₃N₄) were investigated for OER properties by first-principles calculations. Based on the Gibbs free energy, 2Mn–C₃N₄ possesses higher OER properties, and has a lower over-potential (1.22 V) than Mn–C₃N₄ (2.42 V). 2Mn–C₃N₄ has moderate absorption energies for OH and OOH, which benefits the first one-electron reaction and the O₂ desorption during the OER. Additionally, by analyzing the partial density of states and projected crystal orbital Hamilton population, the anti-bonding states become less occupied and the adsorption strength of OH is enhanced in 2Mn–C₃N₄. Thus, the adsorptive strength of 2Mn–C₃N₄ for OH is stronger than that of Mn–C₃N₄, which causes 2Mn–C₃N₄ to show a higher OER activity. The metal–support interaction can alter the local electronic characteristics. The interaction between the metal active center and the reaction intermediates can influence the OER performance, where the specific orbital hybridization plays an important role. Therefore, our results provide a primary understanding of the influence of orbital hybridization intensity on effective OER catalysts.