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.