Hollow TiO₂/CdS Z‐Scheme Heterojunctions with Spatially Separated Cocatalysts for Highly Selective Photodriven CO₂ Conversion

Photoreduction of CO 2 into fuels and value‐added chemical products represents a promising strategy for achieving carbon cycling. However, the slow kinetics of photoexcited charge‐carrier and the limited selectivity of products inhibit its progress. Herein, a hollow Z‐Scheme heterojunction photocatalyst with spatially separated Co 3 O 4 and CuO x cocatalysts (Co 3 O 4 ‐TiO 2 /CdS‐CuO x ) is successfully engineered for gas‐solid phase CO 2 photoreduction. Under simulated sunlight irradiation, the Co 3 O 4 ‐TiO 2 /CdS‐CuO x heterojunction shows high photocatalytic CO 2 reduction activity with a CO yield up to 124 µmol·h −1 g −1 and a high product selectivity of 98%, which is a 2.4 fold improvement in activity over TiO 2 /CdS. The Z‐Scheme charge transfer with a built‐in electric field between TiO 2 and CdS improves the separation efficiency of photogenerated carriers. The spatial separation of Co 3 O 4 and CuO x cocatalysts not only facilitates the capture of photogenerated holes and electrons, thereby enhancing the water splitting and CO 2 reduction processes, but also weakens the adsorption of CO reaction intermediates, enabling efficient and selective photodriven CO 2 to CO. Furthermore, the hollow structure also provides more active sites for the adsorption and activation of and H 2 O and CO 2 molecules. Experimental results and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed the key reaction intermediates and inferred the reaction pathway.