Abstract
The surface electron density significantly affects the photocatalytic efficiency, especially the photocatalytic CO2 reduction reaction, which involves multi-electron participation in the conversion process. Herein, we propose a conceptually different mechanism for surface electron density modulation based on the model of Au anchored CdS. We firstly manipulate the direction of electron transfer by regulating the vacancy types of CdS. When electrons accumulate on vacancies instead of single Au atoms, the adsorption types of CO2 change from physical adsorption to chemical adsorption. More importantly, the surface electron density is manipulated by controlling the size of Au nanostructures. When Au nanoclusters downsize to single Au atoms, the strong hybridization of Au 5d and S 2p orbits accelerates the photo-electrons transfer onto the surface, resulting in more electrons available for CO2 reduction. As a result, the product generation rate of AuSA/Cd1−xS manifests a remarkable at least 113-fold enhancement compared with pristine Cd1−xS.
Highlights
The surface electron density significantly affects the photocatalytic efficiency, especially the photocatalytic CO2 reduction reaction, which involves multi-electron participation in the conversion process
Photocatalytic CO2 conversion technology has attracted extensive interest, since the conversion of CO2 into high value-added chemicals could potentially be achieved under relatively mild conditions, which facilitates its resource utilization[3,4]
With in-depth research, it is further found that electron transfer is tremendously dependent on the size of metal nanostructures or the type of local coordination[16,17]
Summary
The surface electron density significantly affects the photocatalytic efficiency, especially the photocatalytic CO2 reduction reaction, which involves multi-electron participation in the conversion process. The above considerations suggest that controlling the size of metal nanostructures and/or the type of vacancies might realize the accumulation of electrons at other sites instead of metal nanostructures, which is likely to promote the adsorption and conversion of CO2. For this purpose, CdS is selected to be a model material due to the easy-fabricated vacancies and favorable solar light response[20,21,22]. Benefiting from this, CO2 could be chemically bonded on the Cd vacancies instead of physical adsorption on single Au atoms to promote its effective activation
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