Multifunctional Single-Atom Catalysts on N- and P-Doped Triphenylene-Graphdiyne for Water Splitting and Oxygen Reduction

Single-atom catalysts (SACs) supported on 2D carbon materials are promising platforms for efficient and multifunctional electrocatalysis. Here, dispersion-corrected density functional theory (DFT) calculations were performed to investigate the HER, OER, and ORR activities of transition- and post-transition-metal single atoms anchored on N- and P-doped triphenylene-graphdiyne (N-TpG and P-TpG) under both solvated and vacuum conditions. Reaction free-energy diagrams, overpotentials, and 2D volcano plots were utilized to determine activity trends and identify the rate-determining steps. In contrast to graphene-based systems, the d-band center does not serve as a reliable descriptor for TpG-supported SACs, whereas the proposed descriptor ψ shows only a moderate correlation with Δ G OH* . Importantly, multiple systems demonstrate multifunctional activity. Under solvated conditions, Rh-, Co-, and Cu@N-TpG, as well as Cu-, Ga-, Pd-, and Ru@P-TpG, fall within the optimal window for bifunctional HER/OER catalysis, whereas Ag-, Rh-, and Ni@N-TpG, along with Sn-, Pd-, and Ag@P-TpG, emerge as promising ORR/OER bifunctional catalysts. Notably, Rh@N-TpG and Pd@P-TpG exhibit outstanding trifunctional (HER/OER/ORR) performance. Pourbaix analysis indicates that surface coverage evolves with potential, with optimal catalysts achieving a balanced adsorption of H*, OH*, and O* intermediates under realistic electrochemical conditions. These findings provide structure−activity insights and design guidelines for next-generation multifunctional electrocatalysts for water splitting and metal−air batteries.