Thiophene-doped resorcinol-formaldehyde resin photocatalyst for efficient H2O2 production via enhanced selectivity toward two-electron ORR pathway

Abstract

Resorcinol-formaldehyde (RF) resin is a promising photocatalytic material that is capable of converting O2 and H2O into hydrogen peroxide (H2O2) without generating by-products. Quinone unit serves as an active site for the oxygen reduction reaction (ORR) channel, which plays the key role in the photocatalytic H2O2 production. However, the quinone unit has excessively strong adsorption of the *OOH intermediate, resulting in poor selectivity of the RF resin toward the two-electron ORR pathway, which limits its ability to exhibit excellent artificial photocatalytic performance in H2O2 synthesis. In this study, a thiophene-resorcinol-formaldehyde (TRF) resin photocatalyst was developed by incorporating the thiophene, which acts as a highly selective ORR site to enhance the selectivity of two-electron ORR channel. Additionally, thiophene facilitates the formation of thiophene-resorcinol-quinone units that effectively promote the photogenerated carrier separation. Consequently, the TRF resin demonstrates remarkable photocatalytic H2O2 production activity, and the yield reaches 301.8 μmol L−1, which is approximately 1.5 times that of the RF resin under identical conditions. The rotating disk electrode (RDE) tests demonstrate that this resin exhibits significantly enhanced two-electron ORR selectivity. The density functional theory (DFT) calculations exhibit that the thiophene ring acts as an active site for the ORR pathway, and the thiophene unit exhibits moderate adsorption strength towards *OOH intermediate. This work provides a novel approach to designing the photocatalyst with high two-electron ORR selectivity at the molecular level, thereby enabling the efficient and stable photocatalytic production of H2O2.