First-principles study of electrochemical H₂O₂ production on Pd-B₄₀ single-atom catalyst

Hydrogen peroxide (H₂O₂), a versatile green compound, is increasingly in demand. The electrochemical two-electron oxygen reduction reaction (2e^- ORR) is a simple and environmentally friendly substitute method to the traditional anthraquinone oxidation method for H₂O₂ production. This study systematically investigates the 2e^- ORR process on single transition metal atom-loaded boron fullerene (M - B₄₀) using density functional theory calculations. In evaluating the stability of the catalysts, we found that Au, Pd, Pt, Rh, and Ir atoms adsorbed on hexagonal or heptagonal sites of B₄₀ exhibit good stability. Among these, Pd-modified B₄₀ heptagonal cavity (Pd-B₄₀-heptagonal) demonstrates an ideal Gibbs free energy change for OOH* (4.49 eV) and efficiently catalyzes H₂O₂ production at a low overpotential (0.27 V). Electronic structure analysis reveals that electron transfer between Pd-B₄₀-heptagonal and adsorbed O₂ facilitates O₂ activation. Additionally, the high 2e^- ORR activity of Pd-B₄₀-heptagonal is attributed to electron transfer from the Pd-d orbitals to the π* anti-bonding of p orbitals of OOH*, moderately activating the O-O bond. This study offers valuable understanding designing high-performance electrocatalysts for 2e^- ORR.