High-efficient OER/ORR bifunctional electrocatalyst based on single transition-metal anchored Graphynes: Key descriptors under acceptance-backdonation mechanism framework

The development of highly efficient, nonprecious, single-metal-atom-based bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is of great significance for various energy conversion devices. Using the first-principles calculations, we have designed a series of single transition metal (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Nb, Mo, Ru, Rh, Pd and Pt) anchored graphyne systems (TM-TEB). Notably, Ni-TEB and Pd-TEB emerge as promising candidates for OER/ORR bifunctional electrocatalysts, exhibiting lower overpotentials (η_OER, η_ORR) of (0.47, 0.44 V) and (0.36, 0.30 V), respectively, which rival ideal performance of IrO₂ for OER (0.56 V) and Pt for ORR (0.45 V). The superior catalytic activity is attributed to the favorable interactions between the active sites and the oxygen-containing intermediates, facilitating the adsorption and desorption during the catalytic process. The “acceptance-backdonation” mechanism effectively explains these interactions, originating from the moderate p-d orbital hybridization that governs electron transfer and redistribution between TM and adsorbed oxygen atom. This can be quantitatively elucidated through the surface-to-intrinsic descriptors analysis, including adsorption free energy (ΔG_ads), the number of d electrons (θ_e), ICOHP, charge transfer (ΔCharge), φ and ε. These intriguing results may inspire further exploration of bifunctional catalysts for energy storage and conversion applications.