External-Shell Oxygen Enabling the Local Environment Modulation of Unsaturated NbN₃ for Efficient Electrosynthesis of Hydrogen Peroxide

Abstract

Single-atom catalysts with a tunable coordination structure have shown grand potential in flexibly altering the selectivity of oxygen reduction reaction (ORR) toward the desired pathway. However, rationally mediating the ORR pathway by modulating the local coordination number of the single-metal sites is still challenging. Herein, we prepare the Nb single-atom catalysts (SACs) with an external-shell oxygenmodulated unsaturated NbN 3 site in carbon nitride and the NbN 4 site anchored in nitrogen-doped carbon carriers, respectively. Compared with typical NbN 4 moieties for 4e − ORR, the as-prepared NbN 3 SACs exhibit excellent 2e − ORR activity in 0.1 M KOH, with the onset overpotential close to zero (9 mV) and the H 2 O 2 selectivity above 95%, making it one of the state-of-the-art catalysts in the electrosynthesis of hydrogen peroxide. Density functional theory (DFT) theoretical calculations indicate the unsaturated Nb−N 3 moieties and the adjacent oxygen groups optimize the interface bond strength of pivotal intermediates (OOH*) for producing H 2 O 2 , thus accelerating the 2e − ORR pathway. Our findings may provide a novel platform for developing SACs with high activity and tunable selectivity.

Single-atom catalysts for the photocatalytic and electrocatalytic synthesis of hydrogen peroxide

“…Furthermore, by combining in-situ characterization and DFT calculations, the reaction mechanism of H2O2 production from SACs can be further elaborated. For example, Li et al [65] prepared Nb single-atom electrocatalysts (NbN3-(O)C3N4/carboxyl-functionalized multi-walled carbon nanotubes (OCNT)) with shell oxygen-modulated unsaturated NbN3 groups in carbon nitride. These electrocatalysts were studied using in-situ Raman spectroscopy and DFT calculations and compared with NbN4/NC single-atom electrocatalysts with saturated N coordination to further investigate the effect of NbN3 sites on ORR pathway modulation.…”