Photo-charge regulation of metal-free photocatalyst by carbon dots for efficient and stable hydrogen peroxide production

Abstract

Solar-driven water splitting for hydrogen peroxide (H₂O₂) production is a sustainable and ultra-clean method. It is difficult for a single-component photocatalyst to meet all the requirements for efficient and stable photoproduction of H₂O₂. Meanwhile, for multiple-component catalysts, a huge and urgent challenge is to adjust the photo-charge between the multiple components and interfaces of catalysts. Herein, we report a metal-free photocatalyst CN_1.8/ICT/CDs composed of CN_1.8, organic small molecules (ICT) and N, S-doped carbon dots (CDs) to produce H₂O₂ efficiently and stably through a dual-channel process. In this catalyst system, CDs are first reported as the active site of water oxidation reaction (WOR) and ICT as the active site of oxygen reduction reaction (ORR), with greatly improved efficiency of the use of photo-charge, and the poisoning of CN_1.8/ICT/CDs by H₂O₂ was prevented. In situ transient photovoltage measurements (TPV) further revealed the photo-charge regulation function of CDs in this multiple-component metal-free photocatalyst. As a result, the CN_1.8/ICT/CDs catalyst exhibits a prominent H₂O₂ production rate of 2202.81 μmol h⁻¹ g⁻¹ (λ ≥ 420 nm), which represents the most efficient H₂O₂ production rate from a metal-free photocatalyst in air atmosphere without sacrificial agents. This work also provides a valid TPV-based method for a deep understanding of complex photocatalytic systems.