Resolving Charge Recombination and Intermediate Stabilization: A Rational Design of In₂O₃/TiO₂ S-Scheme Heterojunction for Efficient CH₄ Production

Abstract

Photocatalytic CO₂ reduction to CH₄ is regarded as one of the most promising strategies for mitigating environmental and energy challenges, offering a sustainable pathway toward achieving carbon neutrality. However, its practical application is hindered by low catalytic performance and product selectivity, primarily owing to inefficient electron transfer and insufficient stabilization of key reaction intermediates. Herein, an S-scheme heterojunction of In₂O₃/TiO₂ is synthesized via a two-step method to enhance photogenerated charge carrier separation and transfer. The optimized photocatalyst demonstrates exceptional performance, achieving a CH₄ yield of 64.1 µmol g⁻¹ h⁻¹ accompanied by an ultrahigh electron selectivity of 96.0%. The integration of density functional theory (DFT) calculations with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses demonstrates that the heterojunction significantly enhances CO₂ activation, as evidenced by the upshifted d-band center and increased crystal orbital Hamilton population (COHP) values. Furthermore, the In₂O₃/TiO₂ heterojunction exhibits enhanced adsorption of CO₂ and key intermediates, thereby improving reaction kinetics and thermodynamics. These properties facilitate the hydrogenation of *COOH, ultimately promoting CH₄ generation. This work not only provides a mechanistic understanding of S-scheme heterojunctions in CO₂ photoreduction but also provides a new design strategy for developing highly efficient photocatalysts.

Keywords

CH₄ production / charge transfer In₂O₃/TiO₂ catalyst / photocatalytic CO₂ reduction / S-scheme heterojunction

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