Dual effect of the coordination field and sulphuric acid on the properties of a single-atom catalyst in the electrosynthesis of H2O2

Abstract

Electrocatalytic synthesis of hydrogen peroxide (H₂O₂) via the two-electron oxygen reduction reaction (2e⁻ ORR) is the ideal solution for on-site H₂O₂ production. Herein, we propose a new strategy for creating new 2e⁻ ORR catalysts by introducing electron-deficient B atoms and electron-rich N atoms to regulate the coordination field of metal ions on a graphene substrate. Through the first-principles density functional theory (DFT) calculations, NiN₂B₂-h was screened out as it had a low overpotential (0.12 V) for 2e⁻ ORR. The Bader charge analysis revealed that B atoms increased the charge density of Ni atoms, leading to moderate binding of O₂. Furthermore, the combination of ab initio molecular dynamic (AIMD) calculations and DFT calculations in an H₂SO₄ environment revealed a new reaction mechanism of H₂O₂ synthesis, involving proton-transfer between activated O₂ and HSO₄⁻. Moreover, the rate-determining step (0.63 eV) of H₂O₂ desorption in the presence of H₂SO₄ was different from that of OOH* protonation (0.45 eV) under the gas phase. This difference is attributed to the hydrogen-bond network in the acid solution.