Ti³⁺ Defective TiO₂/CdS Z-Scheme Photocatalyst for Enhancing Photocatalytic CO₂ Reduction to C1–C3 Products

Photocatalytic CO2 reduction is a promising route to simultaneously address two critical issues related to the energy and environment. Herein, a direct Z-scheme photocatalytic system, Ti3+ defective TiO2/CdS nanoflowers, was fabricated to enhance the production of C1–C3 products from CO2 reduction. First, nanoflower-like TiO2 (NF-TiO2) is prepared using a TiB2 precursor to build in Ti3+ defects. Then, the NF-TiO2/CdS heterojunctions are constructed via the sulfurization of TiO2/Cd-MOF. Importantly, the optimal heterojunction photocatalyst NF-TiO2/CdS0.6 exhibits a highly promoted CO2 reduction activity not only for CO and CH4 but also for C2–C3 hydrocarbons. The cumulative yields of CO and CH4 are 1007.0 μmol/g and 83.5 μmol/g (2.5 h), respectively, and a yield of 55.3 μmol/g (2.5 h) of C2–C3 hydrocarbons is obtained. This enhanced yield of C1–C3 products is attributed to the synergistic effects of abundant Ti3+ defects that increase adsorption and activation of CO2, the large surface area that provides sufficient active sites, and a direct Z-scheme heterojunction with a good intimate contact interface that effectively separates charge carriers and accumulates electrons with strong reducibility. Moreover, the photoluminescence analysis of hydroxyl radicals was conducted to provide evidence for the direct Z-scheme mechanism. This work provides a facile method for the construction of a TiO2-based direct Z-scheme photocatalytic system for improving photocatalytic performance toward CO2 reduction.

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