Engineering Three-Dimensional (3D) Out-of-Plane Graphene Edge Sites for Highly Selective Two-Electron Oxygen Reduction Electrocatalysis

Selective two-electron oxygen reduction reaction (ORR) offers a promising route for hydrogen peroxide synthesis, and defective sp2-carbon-based materials are attractive, low-cost electrocatalysts for this process. However, due to a wide range of possible defect structures formed during material synthesis, the identification and fabrication of precise active sites remain a challenge. Here, we report a graphene edge-based electrocatalyst for two-electron ORR-nanowire-templated three-dimensional fuzzy graphene (NT-3DFG). NT-3DFG exhibits notable efficiency [onset potential of 0.79 +/- 0.01 V vs reversible hydrogen electrode (RHE)], high selectivity (94 +/- 2% H2O2), and tunable ORR activity as a function of graphene edge site density. Using spectroscopic surface characterization and density functional theory calculations, we find that NT-3DFG edge sites are readily functionalized by carbonyl (C=0) and hydroxyl (C-OH) groups under alkaline ORR conditions. Our calculations indicate that multiple functionalized configurations at both armchair and zigzag edges may achieve a local coordination environment that allows selective, two-electron ORR We derive a generalized geometric descriptor based on the local coordination environment that provides activity predictions of graphene surface sites within similar to 0.1 V of computed values. We combine synthesis, spectroscopy, and simulations to improve active site characterization and accelerate carbon-based electrocatalyst discovery.