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

Abstract

Developing the heterogeneous photocatalysts with high performance for carbon dioxide (CO2) conversion to solar fuels is remarkably significant for reducing the atmospheric CO2 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 CO2-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-C3N4) 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-C3N4 heterojunction creates the higher density of surface photogenerated electron, dynamically accelerating the multi-electron reduction of CO2. Moreover, the selective photodeposition of CdS on Au/g-C3N4 affords sufficient electron-enriched Sδ− active sites which are more beneficial to the provision of H adatoms. These advantages jointly improve the photocatalytic CO2 conversion to methane (CH4) via a multi-proton coupled multi-electron reduction process. The CH4 yield rate on CdS/Au/g-C3N4 photocatalyst is about twice that of CdS/g-C3N4, while g-C3N4 and Au/g-C3N4 only produce CO. The total electron utilization for CO2 reduction on CdS/Au/g-C3N4 photocatalyst is 6.9 times that of g-C3N4. Furthermore, the CdS/Au/g-C3N4 photocatalyst exhibits high stability in consecutive cycles of CO2 reduction reaction. The photocatalytic mechanism is proposed on the basis of in situ spectrographic analyses together with other detailed characterizations.