Abstract
The generation of H+ by active species attacking proton donor (PD) is a key step in photocatalytic H2O2 production (PHP). Deeply analyzing the involved mechanism may be a crucial factor to break through the bottleneck of H2O2 yield. Here, nitrogen-deficient and boron-doped g-C3N4 are synthesized for PHP and the interaction mechanisms between active species and PD are revealed. The prepared photocatalyst exhibits a high H2O2 production rate (455 μM h−1 g−1). The 1O2, •O2- and hole promoted by modification site dominate twelve different reaction mechanisms, respectively. For the oxidation pathways dominated by hole, H2O2 generation is limited by the dissociation of PD or desorption of H+ on catalyst surface. Interestingly, •O2- and 1O2 could directly attack PD, or diffuse into solution to react with PD to produce H2O2 with lower barriers. Moreover, there is a synergistic effect between doped-boron, 1O2 and water bridge, which further reduces the reaction barrier.
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•For the oxidation pathways driven by h+, H2O2 generation is limited by the dissociation of proton donor or desorption of H+.•The surface •O2- and 1O2 can directly attack proton donor, or diffuse into solution to react with it to generate H2O2.•The 1O2 on doped-boron site can further reduce the barrier of H2O2 generation with assistance of surrounding water molecules.•Free •O2- can promote H2O2 generation with the lowest energy barrier among the ten favorable reaction pathways.