Solar-to-hydrogen peroxide conversion of photocatalytic carbon dots with anthraquinone: Unveiling the dual role of surface functionalities

Solar-driven photocatalytic production of hydrogen peroxide (H₂O₂) requires only sunlight, oxygen, and water, making it a green and sustainable alternative to conventional H₂O₂ production processes. We present photocatalytic carbon dots (CDs) as a new candidate for high-performance H₂O₂ production. Owing to the generation of an excellent charge carrier and the presence of various oxygen-containing functional groups, CDs showed an outstanding H₂O₂ production capability of 609.4 μmol g⁻¹ h⁻¹ even in the absence of an electron donor, demonstrating promising self-electron-donating capabilities. Hydroxyl groups on their surface, in particular, serve a dual role as photocatalytic active sites and as electron and proton donors toward the oxygen reduction reaction (ORR). The photocatalytic activity of CDs was significantly improved to 1187.8 μmol g⁻¹ by functionalizing their surfaces with anthraquinone (AQ) as a co-catalyst; it promoted the charge carrier separation and electrochemically favored the two-electron pathway of ORR. These carbon-based metal-free nanohybrids that are a unique combination of CDs and AQ could offer insights into designing efficient photocatalysts for future solar-to-H₂O₂ conversion systems.