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

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/TiO(2 )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 mu mol 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.