Boosted selective photooxidation of methane to methanol on Bi2S3/BiOCl-OV heterojunctions with atomic co-sharing interface via synergy of S-scheme charge transfer and photothermal effect

Abstract

Solar-driven photocatalysis offers an energy-saving route for selective conversion of relatively inert methane (CH₄) into active chemical fuels such as methanol (CH₃OH), nevertheless CH₄ oxidation activity and CH₃OH selectivity of single photocatalysis are still low. Photothermal synergistic catalysis can maximize the utilization of solar energy to yield charge carriers and synchronously afford heat input, representing a potential strategy for boosting CH₄ photooxidation. Herein, full-spectrum-responsive Bi₂S₃/BiOCl-O_V catalysts with coshared Bi atoms and rich oxygen vacancies (O_V) were in-situ constructed via anion exchange approach, where Bi₂S₃ served as photo-to-thermal conversion material and concurrently formed S-scheme heterojunction with BiOCl. In-situ generated O_V in anion-exchange process promoted CH₄ adsorption and activation. Atomic-level interface channel via cosharing of Bi atoms decreased interfacial resistance and further boosted charge migration. Photogenerated charge carriers with strong redox capacity triggered CH₄ oxidation and CH₃OH production, meanwhile the photoinduced heat by Bi₂S₃ harnessing near-infrared light enhanced active species generation and catalysis kinetics. Owing to the synergistic effects of S-scheme charge transfer and photo-to-thermal conversion, the optimal 0.7-Bi₂S₃/BiOCl exhibited impressive CH₃OH productivity of 11.83 mmol/g with high selectivity of 90.2 % after 2 h irradiation of simulated sunlight, significantly outperforming pristine BiOCl (4.01 and 1.98 times) and most recently reported photocatalysts. More than that, the CH₃OH productivity reached up to 10.79 mmol/g with a selectivity of 89.5 % under concentrated outdoor natural sunlight. Performance enhancing mechanism was elucidated through in-situ characterizations and DFT calculation. This study provides meaningful guidance to construct photothermal catalysts with high-quality interface for efficient photooxidation of CH₄ to CH₃OH.

Keywords: CH(3)OH production; CH(4) oxidation; Photothermal catalysis; S-scheme heterojunction; Synergistic effects.