  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,
identification and fabrication of precise active sites remain a challenge.
Here, we report a graphene edgebased electrocatalyst for two-electron ORR -
nanowire-templated three-dimensional fuzzy graphene (NT3DFG). NT-3DFG exhibits
excellent efficiency (onset potential of 0.79 $\pm$ 0.01 V versus RHE),
selectivity (93 $\pm$ 3 % 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=O) and hydroxyl (C-OH) groups under
alkaline ORR conditions. Our calculations indicate that multiple site
configurations at both armchair and zigzag edges may achieve a local
coordination environment that allows selective, two-electron ORR. We derive a
general geometric descriptor based on the local coordination environment that
provides activity predictions of graphene surface sites within ~0.1 V of
computed values. Herein we combine synthesis, spectroscopy, and simulations to
improve active site characterization and accelerate carbon-based
electrocatalyst discovery.
