Iodide ions as invisible chemical scissors tailoring carbon nitride for highly efficient photocatalytic H2O2 evolution

Abstract

Graphitic carbon nitride (g-C₃N₄) being a non-metallic oxygen reduction reaction (ORR) photocatalyst has attracted much attention in the generation of H₂O₂. Nevertheless, the weak O₂ adsorption capacity and inefficient separation of charge carriers greatly restrict the production efficiency of H₂O₂. Herein, iodine ions were used as invisible chemical scissors to tailor the tubular g-C₃N₄ (TCN) precursor, and relatively ultrathin g-C₃N₄ nanosheets were prepared (TCN/NaI). The obtained TCN/NaI exhibits alkali metal (Na⁺) and hydroxyl (–OH) co-modification, and shows the highest H₂O₂ generation rate (1935.61 μM h⁻¹), greatly exceeding that of bulk g-C₃N₄ (BCN, 31.96 μM h⁻¹) and TCN (129.32 μM h⁻¹). In addition, excited states calculations of BCN + O₂ and TCN/NaI + O₂ further reveal that the electron of the β spin–orbital in TCN/NaI can transfer to the π* orbital of O₂ more easily than that in BCN, thus enhancing the activation of O₂. This work not only provides in-depth insights into the photocatalytic ORR for the H₂O₂ production mechanism, but also shows that the synergy of structure modification and doping can be further expanded to other semiconductors for photocatalytic applications.