H2O2 Photosynthesis from H2O and O2 under Weak Light by Carbon Nitrides with Piezoelectric Effect

Driven by the essential need of a green, safe, and low-cost approach to producing H2O2, a highly valuable multifunctional chemical, artificial photosynthesis emerges as a promising avenue. However, current catalyst systems remain challenging, due to the need of high-density sunlight, poor selectivity/activity, or/and unfavorable thermodynamics. Here, we reported that an indirect 2e- water oxidation reaction (WOR) in photocatalytic H2O2 production was unusually activated by C5N2 with piezoelectric effects. Under ultrasonication, C5N2 exhibited an overall H2O2 photosynthesis rate of 918.4 µM/h and an exceptionally high solar-to-chemical conversion efficiency of 2.6% after calibration under weak light (0.1 sun). Mechanism studies showed the piezoelectric effect of carbon nitride overcame the high uphill thermodynamics of *OH intermediate generation, which opened a new pathway for 2e- WOR, the kinetic limiting step in the overall H2O2 production from H2O and O2. Benefiting from the high efficiency of photocatalytic H2O2 production under weak light, the concept was further successfully adapted to biomedical applications in efficient sono-photo-chemodynamic therapy of tumors.