A metal-free photocatalyst for highly efficient hydrogen peroxide photoproduction in real seawater

Artificial photosynthesis of H₂O₂ from H₂O and O₂, as a spotless method, has aroused widespread interest. Up to date, most photocatalysts still suffer from serious salt-deactivated effects with huge consumption of photogenerated charges, which severely limit their wide application. Herein, by using a phenolic condensation approach, carbon dots, organic dye molecule procyanidins and 4-methoxybenzaldehyde are composed into a metal-free photocatalyst for the photosynthetic production of H₂O₂ in seawater. This catalyst exhibits high photocatalytic ability to produce H₂O₂ with the yield of 1776 μmol g⁻¹h⁻¹ (λ ≥ 420 nm; 34.8 mW cm⁻²) in real seawater, about 4.8 times higher than the pure polymer. Combining with in-situ photoelectrochemical and transient photovoltage analysis, the active site and the catalytic mechanism of this composite catalyst in seawater are also clearly clarified. This work opens up an avenue for a highly efficient and practical, available catalyst for H₂O₂ photoproduction in real seawater.