Efficient photocatalytic H2O2 generation utilizing surface functional duality in carbon dots-polydopamine heterojunctions

Abstract

Designing efficient, metal-free photocatalysts for selective hydrogen peroxide (H2O2) production via the two-electron oxygen reduction reaction (2e⁻ ORR) is crucial for sustainable chemical processes. Herein, we report a carbon dots–polydopamine (CD/PDA) heterojunction system that exhibits outstanding photocatalytic performance by leveraging the surface functional duality of the organic components. The CD/PDA8 composite demonstrates the highest H2O2 production rate of 1408 μmol g⁻¹ h⁻¹ under visible light irradiation, significantly outperforming pristine CD and PDA. Mott–Schottky and optical analyses confirm the formation of a type-II heterojunction, which enables efficient charge separation. In this architecture, CD serves as the primary electron-accepting active sites for O₂ reduction, while PDA—rich in surface catechol and hydroxyl groups—facilitates hole scavenging without requiring external electron donors as well as active sites. This dual-functionality not only suppresses electron–hole recombination but also minimizes side reactions, enhancing the selectivity and stability of the H₂O₂ generation process. Moreover, the catalyst exhibits excellent photocatalytic performance, recyclability and structural integrity over multiple cycles. These findings highlight the potential of surface-functionalized, all-organic heterojunctions as highly selective and sustainable photocatalysts for green chemical applications.