Efficient, Selective CO₂ Photoreduction Enabled by Facet-Resolved Redox-Active Sites on Colloidal CdS Nanosheets

Abstract

Advances in nanotechnology have enabled precise design of catalytic sites for CO 2 photoreduction, pushing product selectivity to near unity. However, activity of most nanostructured photocatalysts remains underwhelming due to fast recombination of photogenerated electron−hole pairs and sluggish hole transfer. To address these issues, we construct colloidal CdS nanosheets (NSs) with the large basal planes terminated by S 2− atomic layers as intrinsic photocatalysts (CdS−S 2− NSs). Experimental investigation reveals that the S 2− termination endows ultrathin CdS−S 2− NSs with facet-resolved redoxcatalytic sites: oxidation occurs on S 2− -terminated large basal facets and reduction happens on side facets. Such an allocation of redox sites not only promotes spatial separation of photoinduced electrons and holes but also facilitates balanced extraction of holes and electrons by shortening the hole diffusion distance along the (001) direction of the ultrathin NSs. Consequently, the CdS−S 2− NSs exhibit superb performance for photocatalytic CO 2 -to-CO conversion, which was verified by the isotope-labeled experiments to be a record-breaking performance: a CO selectivity of 99%, a CO formation rate of 2.13 mol g −1 h −1 , and an effective apparent quantum efficiency of 42.1% under the irradiation (340 to 450 nm) of a solar simulator (AM 1.5G). The breakthrough performance achieved in this work provides novel insights into the precise design of nanostructures for selective and efficient CO 2 photoreduction.

Combing Hollow Shell Structure and Z-Scheme Heterojunction Construction for Promoting CO2 Photoreduction

“…As shown in Figure e and Figure S16, the peaks at 1246.5 cm –1 , 1429.5 cm –1 , and 1367.5 cm –1 are attributed to HCO 3 – and m-CO 3 2– adsorbed on CdS, respectively. These results confirm the adsorption of CO 2 on the CdS surface in the form of monodentate carbonate. − Significantly, the peaks located at 1148 cm –1 and in the range 1500–1550 cm –1 correspond to *COOH adsorbed on the CdS surface, − and the peak located at 2076 cm –1 corresponds to *CO, (Figure S17) which is the key intermediate for CO 2 photoreduction to produce CO. , The in-situ DRIFT peak intensity of CdS/Au/DHCZ corresponding to *COOH enhanced obviously after light irradiation, providing strong evidence for photocatalytic CO 2 hydrogenation. Subsequently, *COOH will be further hydrogenated and dehydrated to form CO.…”

Ultrathin CdS@BDC nanosheets derived from 2D metal–organic frameworks for enhanced photoinduced-stability and photocatalytic hydrogen production

“…6A). Then, due to the two-dimensional skeleton structure on the surface of CdS@BDC NSs and a large number of exposed S 2− ions, this supported the photo-excited electrons and holes to migrate to the spatially separated reduction center (at the small edge) and oxidation center (at the large base surface) 53. On one hand, it is well known that S 2− /SO 3 2− has been widely used as an excellent sacrificial reagent for effectively consuming photogenerated holes in the photocatalytic H 2 evolution of CdS photocatalysts, in which S 2− ions can be oxidized into solid S 0 by photogenerated holes at first, and then converted into S 2 O 3 2− ions together with SO 3 2− (Fig.…”

“…Then, due to the two-dimensional skeleton structure on the surface of CdS@BDC NSs and a large number of exposed S 2ions, this supported the photo-excited electrons and holes to migrate to the spatially separated reduction center (at the small edge) and oxidation center (at the large base surface). 53 On one hand, it is well known that S 2-/SO3 2has been widely used as an In view of the above research on synthesis method and hydrogen production performance of CdS@BDC NSs, it is speculated that this synthesis strategy and the corresponding photocatalytic enhancement mechanism are also universal in other 2D MOF-based nanomaterials. Therefore, we further synthesized Zn-MOF NSs and corresponding ZnS@BDC NSs (Fig.…”

Colloidal semiconductor nanocrystals: from bottom-up nanoarchitectonics to energy harvesting applications

“…353,357 Wang et al developed a novel S 2− termination that endows ultrathin CdS–S 2− nanosheets with facet-resolved redox catalytic sites where oxidation occurs on S 2− -terminated large basal facets and reduction happens on side facets, promoting spatial separation of electrons and holes. 369 CdS–S 2− nanosheets exhibited superb performance for photocatalytic CO 2 -to-CO conversion with a quantum efficiency of 42.1%. 369 Further, the effect of NCs morphology on COOR activity was investigated.…”

“…369 CdS–S 2− nanosheets exhibited superb performance for photocatalytic CO 2 -to-CO conversion with a quantum efficiency of 42.1%. 369 Further, the effect of NCs morphology on COOR activity was investigated. 2D CdS–S 2− nanosheets were compared with zero-dimensional (0D) CdS–S 2− QDs and one-dimensional (1D) CdS–S 2− nanorods.…”