Enhanced charge carrier transport in TiO2/COF S-scheme heterojunction for efficient photocatalytic H2O2 production

Abstract

Hydrogen peroxide (H₂O₂) is a crucial oxidant with diverse industrial applications, yet its conventional synthesis suffers from high energy consumption and hazardous byproducts. Photocatalysis offers a sustainable alternative, but its efficiency is often compromised by rapid charge recombination. Herein, we reported the rational design of a TiO₂/TD-COF S-scheme heterojunction, which achieved a remarkable H₂O₂ production rate of 2162.3 μmol g⁻¹ h⁻¹, representing almost 14-fold enhancement compared to pristine TiO₂. Through in-situ irradiated X-ray photoelectron spectroscopy (ISI-XPS) and femtosecond transient absorption spectroscopy (fs-TAS), we demonstrate an ultrafast charge transfer driven by internal electric field (IEF) that efficiently separates photogenerated carriers while preserving their redox potentials. Furthermore, in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and electron paramagnetic resonance (EPR) spectroscopy provide direct experimental evidence for the dual-pathway mechanism, involving both the oxygen reduction reaction (ORR) and water oxidation reaction (WOR). This work demonstrates the potential of S-scheme heterojunction in overcoming the limitations of traditional photocatalytic systems, offering a scalable and sustainable approach for solar-driven H₂O₂ production.