Hollow TiO ₂ /CdS Z‐Scheme Heterojunctions with Spatially Separated Cocatalysts for Highly Selective Photodriven CO ₂ Conversion

Abstract 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.