Interface photo-charge kinetics regulation by carbon dots for efficient hydrogen peroxide production

Abstract

Hydrogen peroxide (H₂O₂) is a multi-functional chemical for a range of industries, but the present H₂O₂ production requires complex processes, and leads to environmental pollution, etc. Solar water-splitting is one of the potential avenues to combine H₂O and O₂ into H₂O₂ through a cheap and clean way. Most of the photocatalysts involve multiple components and interfaces to improve the catalytic activity and energy conversion efficiency. However, it is difficult to regulate the photo-charge kinetics between the multi-interface catalyst, which hinders the practical application of photocatalysts. Here, we report a SnS₂/In₂S₃ type II heterostructure modified by carbon dots (SnS₂/In₂S₃/CDs) to highly improve the stability of sulfides and realize generation of H₂O₂ by the oxygen reduction reaction (ORR). Notably, in situ transient photovoltage measurements (TPV) were carried out to analyze the charge transfer process among SnS₂, In₂S₃ and CDs. The optimal SnS₂/In₂S₃/CD composite (n(Sn):n(In) = 50%) displays a prominent H₂O₂ production rate of 1111.89 μmol h⁻¹ g⁻¹ without any sacrificial agent under the conditions of normal pressure and neutral solution (pH = 7). The quantum efficiency (QE) of H₂O₂ production was calculated to be 3.9% under light (λ = 535 nm), and the solar energy conversion efficiency (SCC) was up to 1.02%, which is the highest known production of H₂O₂ from sulfides as photocatalysts. Our work provides a new way to regulate the photo-charge kinetics of the multi-interface catalyst using CDs to achieve the extremely efficient production of H₂O₂ by photocatalytic water-splitting.