Unlocking the Charge-Migration Mechanism in S-Scheme Junction for Photoreduction of Diluted CO₂ with High Selectivity

The rational design of an S-scheme heterojunctions in hybrid semiconductors to realize separated charge carriers and sufficient redox ability is considered as an attractive way to achieve high photocatalytic activity in diluted CO2 reduction (DCR). An S-scheme heterojunction formed in the fibrous Ta2O5/Ag2S nanostructures is proposed for improving the photocatalytic performance in DCR under simulated solar irradiation. Benchmark CH4 production rates of 132.3 mu mol g(-1) are obtained with 93.1% selectivity over optimal catalyst ASTO-2. The remarkable activity in photocatalytic DCR of Ta2O5/Ag2S is attributed to the unique 0D/1D structure and effective charge separation by the photoinduced strong internal electric field and S-scheme mechanism. The measurements of in situ X-ray photoelectron spectroscopy, femtosecond transient absorption spectroscopy, and electron paramagnetic resonance further confirm the photoinduced carrier transfer pathways following the S-scheme mechanism. This research can provide a new strategy for designing the S-scheme heterojunctions to improve the photocatalytic performance of diluted CO2 conversion.