Zn-doped tubular graphene nitride for visible light and sacrificial-agent-free H2O2 photosynthesis in water

Graphitic carbon nitride (g-C3N4) has become a favored universal photocatalyst. Despite its numerous advantages, the photocatalytic efficiency of g-C3N4 is hindered by the substantial recombination of photoexcited charge carriers and holes. In this work, we demonstrate that Zn-doped tubular carbon nitride photocatalyst (Zn-tCN) can serve as highly efficient catalysts for H2O2 photosynthesis. Mechanism studies confirm that the presence of Zn in g-C3N4 prolongs the lifetimes of photogenerated carriers and inhibits their recombination, which triggers the reduction of O2 to reaction intermediates (O2−), as supported by in situ electron paramagnetic resonance (EPR) spectroscopy. More importantly, sacrificial agent experiments coupled with in situ EPR results confirmed that the reaction mechanism involves a concerted two-electron transfer process. The optimal catalyst displays a H2O2 productivity of 162.4μmol g–1h−1 under visible-light irradiation without a sacrificial agent, which is 11.7 times higher than that of pristine g-C3N4 (13.8μmol g–1h−1). This work proposes a synthetic strategy for the preparation of high-performance Zn-doped g-C3N4, which offers insights and perspectives for developing highly active photocatalysts and deepening the understanding of photocatalytic mechanisms.