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

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 O-2 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 mu M h(-1)), greatly exceeding that of bulk g-C3N4 (BCN, 31.96 mu M h(-1)) and TCN (129.32 mu M h(-1)). In addition, excited states calculations of BCN + O-2 and TCN/NaI + O-2 further reveal that the electron of the beta spin-orbital in TCN/NaI can transfer to the pi* orbital of O-2 more easily than that in BCN, thus enhancing the activation of O-2. 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.

Automated summary

In this study, ultrathin g-C3N4 nanosheets with high H2O2 generation rate were successfully prepared by modifying the g-C3N4 precursor with iodine ions. Moreover, excited states calculations revealed that the modified nanosheets exhibited better O-2 activation ability. This study is of great importance for understanding the mechanism of photocatalytic H2O2 production and exploring the photocatalytic applications of other semiconductors.