Photocatalytic CO2‐to‐CH4 Conversion with Ultrahigh Selectivity of 95.93% on S‐Vacancy Modulated Spatial In2S3/In2O3 Heterojunction

• Published in: Advanced functional materials 2024-12, Vol.34 (49), p.n/a
• Main Authors: Lai, Kezhen, Sun, Yuxin, Li, Ning, Gao, Yangqin, Li, Hui, Ge, Lei, Ma, Tianyi
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Catalysts; Charge density; Density functional theory; Electric fields; Electron transfer; Fourier transforms; Gibbs free energy; Heterojunctions; In2S3/In2O3 heterojunctions; Indium oxides; Methane; Molecular orbitals; Photocatalysis; Polyvinylpyrrolidone; selective CH4 production; Selectivity; vacancy modulated photoreduction; Work functions
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202409031

Photocatalytic conversion of CO2 to methane faces challenges due to the stability of CO2, unpredictable intermediates, and complex electron transfer steps. Herein, a spatial In2S3/In2O3 heterojunction with abundant S vacancies (ISIO(VS)) is obtained through facile Polyvinylpyrrolidone (PVP) treatment to reach a methane yield of 16.52 µmol·g−1·h−1 with a selectivity of 95.93%, which is the highest among reported In2S3 and In2O3 based catalysts. The work function (Wf), differential charge density, and Kelvin Probe Force Microscopy (KPFM) results confirm that S vacancies strengthen the built‐in electric field (BEF) of In2S3/In2O3 (ISIO) heterojunctions, improving carrier separation. Density functional theory (DFT) calculations reveal that S vacancies induce electron redistribution, facilitating adsorption and activation of CO2 and *CO intermediate, thus promoting hydrogenation to yield *CHO. The reaction pathway of photocatalytic CO2 reduction is revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and Gibbs free energy (ΔG). The S vacancies modify electronic orbitals and the highest occupied molecular orbital (HOMO) of In atom, resulting in a stronger interaction between the catalyst and *CHO, which reduces ΔG*CHO and regulates the selectivity of CH4. This study paves a new avenue for the design of photocatalysts with highly selective reduction of CO2 to CH4 through defect engineering. A spatial In2S3/In2O3 heterojunction with S vacancies achieves 95.53% selectivity of CH4 in photocatalytic CO2 reduction. The S vacancies in In2S3/In2O3 heterojunction modulates the electronic structure and HOMO of In atom, facilitating interactions with *CHO, thereby regulating the selectivity of CH4.