Sustainable photocatalytic synthesis of hydrogen peroxide from catechol-formaldehyde resin microspheres modulated by nitrogen-doped carbon dots

Abstract

Compared with traditional anthraquinone oxidation, the photocatalytic 2-electron ORR is an environmentally friendly and efficient alternative to H₂O₂ production. Herein, low-temperature hydrothermally synthesized catechol-formaldehyde resin (CFR) microspheres were readily available as a green energy-saving catalyst, which has the ability to achieve the chemical conversion of O₂ to H₂O₂ without the need for any external energy sources and electron donors. In order to further improve the catalytic performance, we propose a new design of a composite photocatalyst, namely CFR/NCDs-220, which improves the defects of CFR microspheres by combining with nitrogen-doped carbon dots (NCDs-220) of strong reducing ability with the assistance of sunlight, and has become a new candidate for the green and sustainable photoproduction of H₂O₂. The optimal catalyst produced 64 μmol H₂O₂ within 6 h under visible light irradiation with enhanced catalyst cycle stability and H₂O₂ selectivity owing to the photoexcited NCDs-220 acting as the electron donor for o-benzoquinone in the CFR microspheres. The solar-chemical conversion (SCC) efficiency of CFR/NCDs-220 for the photoproduction of H₂O₂ can reach 1.06% within 3 h without any sacrificial agent. The addition of NCDs-220 can achieve the reversible conversion of catechol and o-benzoquinone, thus ameliorating the photogeneration performance of H₂O₂ by the CFR microspheres. CFR/NCDs-220 exhibited a 2-electron reduction path in visible light and a heightened selectivity for H₂O₂ from 23% to 65%. This work highlights the use of solar-assisted NCDs-220 to power the CFR-chemically-catalyzed O₂ to H₂O₂ conversion with long-term cycle stability, providing a simple strategy for the design of catalysts for H₂O₂ production.