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.