Spatially-separated redox sites enabling selective atmospheric CO2 photoreduction to CH4

CO2 photoreduction to high-valued CH4 is highly attractive, whereas the CH4 selectivity and activity, especially under atmospheric CO2, is still unsatisfying. Here, we design spatially-separated redox sites on two-dimensional heterostructured nanosheets with loaded metal oxides, thus achieving high reactivity and selectivity of photocatalytic atmospheric CO2 reduction to CH4. Taking the synthetic In2O3/In2S3 nanosheets with loaded PdO quantum dots as a prototype, quasi in-situ X-ray photoelectron spectra reveal the Pd sites accumulate photogenerated holes for dissociating H2O and the In sites accept photoexcited electrons to activate CO2. Moreover, the Pd-OD bond is confirmed by in-situ Fourier-transform infrared spectra during the D2O labeling experiment, indicating the PdO quantum dots participate in H2O oxidation to supply hydrogen species for CO2 methanation. As a result, in a simulated air atmosphere, the PdO-In2O3/In2S3 nanosheets enable favorable atmospheric CO2-to-CH4 photoreduction with nearly 100% selectivity and ultralong stability of 240 h as well as CO2 conversion of 48.2%. This study opens an approach towards designing photocatalysts with spatially-separated redox sites to achieve efficient oxidation and reduction of CO2 photocatalysis to CH4.