Constructing alkaline microenvironment on catalyst surface for enhanced electrocatalytic synthesis of hydrogen peroxide in a neutral electrolyte

The direct electrochemical synthesis of H2O2 via a two-electron oxygen reduction reaction (2e− ORR) offers a feasible alternative to the energy-intensive anthraquinone oxidation process. Compared to alkaline electrolytes, challenges remain in achieving high 2e− ORR selectivity and activity for electrosynthesis of H2O2 in neutral electrolytes due to the low concentration of OH−, which hinders the effective binding of key intermediate OOH*. Here, we introduced Lewis acid TiO2 to modify carbon black catalyst for adsorbing in-situ generated OH− and created a local alkaline microenvironment for enhancing the 2e− ORR activity and selectivity in neutral electrolytes. H2O2 productivity of TiO2 modified carbon black catalyst (52.5 mmol L−1 h−1) in a neutral electrolyte (0.5 M Na2SO4) at 0.2 V vs. RHE was 1.6 times as much as that of pristine carbon black (33 mmol L−1 h−1), which was similar with that of pristine carbon black (58.4 mmol L−1 h−1) in an alkaline electrolyte (0.1 M KOH). The finite-element method simulations and experiments indicated that TiO2 could enhance local alkalinity to increase the current density for facilitating 2e− ORR. The density functional theory calculations indicated that the introducing of TiO2 into the CB structure could promote the adsorption of O2, facilitate the adsorption of *OOH and reduce the overpotential, resulting in high activity towards 2e− ORR to H2O2. This work proposes a new strategy for optimizing electrode–electrolyte interface to enhance 2e− ORR performance in neutral electrolytes.