N-B-OH Site-Activated Graphene Quantum Dots for Boosting Electrochemical Hydrogen Peroxide Production

Carbon materials are considered promising 2/4 e(-) oxygen reduction reaction (ORR) electrocatalysts for synthesizing H2O2/H2O via regulating heteroatom dopants and functionalization. Here, various doped and functionalized graphene quantum dots (GQDs) are designed to reveal the crucial active sites of carbon materials for ORR to produce H2O2. Density functional theory (DFT) calculations predict that the edge structure involving edge N, B dopant pairs and further -OH functionalization to the B (N-B-OH) is an active center for 2e(-) ORR. To verify the above predication, GQDs with an enriched density of N-B-OH (NBO-GQDs) are designed and synthesized by the hydrothermal reaction of -NH2 edge-functionalized GQDs with H3BO3 forming six-member heterocycle containing the N-B-OH structure. When dispersed on conductive carbon substrates, the NBO-GQDs show H2O2 selectivity of over 90% at 0.7 -0.8 V versus reversible hydrogen electrode in the alkaline solution in a rotating ring-disk electrode setup. The selectivity retains 90% of the initial value after 12 h stability test. In a flow cell setup, the H2O2 production rate is up to 709 mmol g(catalyst)(-1) h(-1), superior to most reported carbon- and metal-based electrocatalysts. This work provides molecular insight into the design and formulation of highly efficient carbon-based catalysts for sustainable H2O2 production.

Automated summary

Carbon materials, specifically graphene quantum dots (GQDs) with heteroatom dopants and functionalization, are studied as promising electrocatalysts for the oxygen reduction reaction (ORR) to produce H2O2. The activity of GQDs in ORR is revealed to be mainly influenced by the N-B-OH structure, which can be enhanced by designing and synthesizing NBO-GQDs with an enriched density of N-B-OH through hydrothermal reactions. NBO-GQDs exhibit high selectivity for H2O2 production and a high production rate, making them superior to other carbon- and metal-based electrocatalysts.