Facet-selective synthesis of cadmium sulfide photocatalysts for high-efficiency CO2 conversion.

The surface of photocatalysts plays a key role in the adsorption and activation of CO₂ molecules. Establishing the conformational relationship between the crystalline phase of the photocatalysts and the CO₂ reduction reaction (CO₂RR) activity is crucial to understanding the catalytic reaction mechanism. Herein, we synthesized CdS catalysts with different exposed crystalline facets (CdS[100], CdS[001], and CdS[111]) using hydrothermal and water bath methods and evaluated their photocatalytic CO₂RR performances. The results showed that CdS[001] displayed an optimal activity with a 203.2 μmol g^-1 h^-1 of CO generation rate compared with CdS[100] and CdS[111]. More importantly, the CdS[001] catalyst shows the best CO selectivity (S_CO: ∼86.6 %) and CO₂ reduction selectivity (S_CO2: ∼95.4 %) compared with CdS[100] (S_CO: 79.3 %; S_CO2: 90.0 %) and CdS[111] (S_CO: 79.6 %; S_CO2: 82.8 %). The optimal CdS[001] catalyst significantly inhibited the competing hydrogen evolution reaction. The adsorption and activation behaviors of CO₂ on various exposed surfaces of CdS are explored in depth based on density functional theory calculations and in-situ Fourier transform infrared spectra measurements. This work provides new insights into understanding the role of facet control in enhancing photocatalytic CO₂ conversion.