Enhancing Photosynthesis Efficiency of Hydrogen Peroxide by Modulating Side Chains to Facilitate Water Oxidation at Low-Energy Barrier Sites.

Abstract

Hydrogen peroxide (H₂O₂) is a crucial oxidant in advanced oxidation processes. In situ, photosynthesis of it in natural water holds the promise of practical application for water remediation. However, current photosynthesis of H₂O₂ systems primarily relies on oxygen reduction, leading to limited performance in natural water with low dissolved oxygen or anaerobic conditions found in polluted water. Herein, a novel photocatalyst based on conjugated polymers with alternating electron donor-acceptor structures and electron-withdrawing side chains on electron donors is introduced. Specifically, carbazole functions as the electron donor, triazine serves as the electron acceptor, and cyano acts as the electron-withdrawing side chain. Notably, the photocatalyst exhibits a remarkable solar-to-chemical conversion of 0.64%, the highest reported in natural water. Furthermore, even in anaerobic conditions, it achieves an impressive H₂O₂ photosynthetic efficiency of 1365 µmol g^-1 h^-1, surpassing all the reported photosynthetic systems of H₂O₂. This remarkable improvement is attributed to the effective relocation of the water oxidation active site from a high-energy carbazole to a low-energy acetylene site mediated by the side chains, resulting in enhanced O₂ or H₂O₂ generation from water. This breakthrough offers a new avenue for efficient water remediation using advanced oxidation technologies in oxygen-limited environments, holding significant implications for environmental restoration.