Cadmium-sulfide/gold/graphitic-carbon-nitride sandwich heterojunction photocatalyst with regulated electron transfer for boosting carbon-dioxide reduction to hydrocarbon

Developing the heterogeneous photocatalysts with high performance for carbon dioxide (CO 2 ) conversion to solar fuels is remarkably significant for reducing the atmospheric CO 2 level and achieving the target of carbon neutrality through the artificial photosynthesis strategies. However, it remains a great challenge for most of the photocatalysts to achieve the CO 2 -to-hydrocarbon conversion via a multi-proton coupled multi-electron reduction process. In this work, the cadmium-sulfide/gold/graphitic-carbon-nitride (CdS/Au/g-C 3 N 4 ) heterojunction photocatalyst with sandwich nanostructures is designedly constructed by a selective two-step photodeposition process. The better separation of photogenerated electrons and holes in CdS/Au/g-C 3 N 4 heterojunction creates the higher density of surface photogenerated electron, dynamically accelerating the multi-electron reduction of CO 2 . Moreover, the selective photodeposition of CdS on Au/g-C 3 N 4 affords sufficient electron-enriched S δ− active sites which are more beneficial to the provision of H adatoms. These advantages jointly improve the photocatalytic CO 2 conversion to methane (CH 4 ) via a multi-proton coupled multi-electron reduction process. The CH 4 yield rate on CdS/Au/g-C 3 N 4 photocatalyst is about twice that of CdS/g-C 3 N 4 , while g-C 3 N 4 and Au/g-C 3 N 4 only produce CO. The total electron utilization for CO 2 reduction on CdS/Au/g-C 3 N 4 photocatalyst is 6.9 times that of g-C 3 N 4 . Furthermore, the CdS/Au/g-C 3 N 4 photocatalyst exhibits high stability in consecutive cycles of CO 2 reduction reaction. The photocatalytic mechanism is proposed on the basis of in situ spectrographic analyses together with other detailed characterizations.