Hierarchically ordered microporous Ag2S QDs-CoOx/NC nanostructures for enhancing photocatalytic CO2 reduction to chemical fuels

Abstract

Rational design of advanced architectural photocatalysts with efficient separation and transfer of photoinduced charge carriers, and well solar light absorption ability is of critical significance for solar energy utilization and CO2-to-fuel conversion. Herein, a novel three-dimensional (3D) ordered hollow-wall hybrid composite (3DOM Ag2S-CoOx/NC) has been developed by integrating ultrafine Ag2S quantum dots (QDs) on the surface of metal–organic frameworks (MOFs)-derived hierarchically ordered macroporous nitrogen-doped carbon skeletons with implanted CoOx nanoclusters (3DOM CoOx/NC). Compared with pristine 3DOM CoOx/NC and traditional ZIF-67-derived CoOx/NC, the constructed 3DOM Ag2S-CoOx/NC composite exhibits remarkable performances toward the photocatalytic conversion of CO2 and H2O vapor without any sacrifice reagents to fuels (CO-66.00 μmol g−1h−1, CH4-1.21 μmol g−1h−1 and C2H4-2.33 μmol g−1h−1) and a higher C2H4 selectivity (16.47%) in the gas–solid system under light irradiation (λ > 420 nm). Impressively, dual Z-scheme charge transfer pathways in the 3DOM Ag2S-CoOx/NC can provide good channels for boosting electron transfer and charge separation. Experimental characterizations combined with density functional theory (DFT) calculations further elucidate that the key role of Ag2S QDs is served as an auxiliary in the 3DOM Ag2S-CoOx/NC catalyst to improve the electronic structure and further facilitate adsorption/activation capacity of CO2 and H2O. Moreover, the multiple photocatalytic mechanisms including related key intermediates and conversion process of CO2 molecules are further identified by in-situ diffuse reflectance infrared fourier transform spectra (DRIFTS). This innovation provides a novel strategy to design well-designed hierarchically porous hybrid structures for photocatalytic CO2 reduction to high-value fuels.