Hydrogen Peroxide Synthesis via Electrocatalytic Water Oxidation on sp3 and sp2 Carbon Materials Mediated by Carbonates and Bicarbonates

H2O2 production on two typical sp3 and sp2 carbon materials [boron-doped diamond (BDD) and graphite] via the electrochemical two-electron water oxidation reaction (2e–WOR) mediated by carbonates and bicarbonates was measured and compared. The results show that BDD exhibits superior selectivity toward the 2e–WOR compared to graphite in both KHCO3 and K2CO3 aqueous solutions. The highest Faraday efficiency (FE) for BDD in KHCO3 is ∼20.1% for 15 min of chronoamperometry measurement among all the potentials tested, while for graphite, it is ∼5.9%. Similarly, BDD achieves a maximum FE of ∼41.2% in K2CO3, while the highest FE of graphite is only ∼10.2%. Carbonate is more beneficial to the generation of H2O2 than bicarbonate for both BDD and graphite. Infrared spectroscopy analysis discovered that the adsorption of carbonate on the catalyst is stronger than that of bicarbonate, and the adsorption of carbonate increases with potential, while that of bicarbonate does not. Density functional theory calculations verify the stronger adsorption of carbonate on BDD and graphite than that of bicarbonate and suggest that the competitive adsorption of carbonates, bicarbonates, water, and hydroxide ions on the surface of catalysts probably essentially affects the performance of H2O2 production.