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/CdS_0.6 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.

中文翻译：

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Ti3+ 缺陷型 TiO2/CdS Z 型光催化剂用于增强光催化 CO2 还原为 C1–C3 产品

光催化CO ₂还原是同时解决与能源和环境相关的两个关键问题的有前景的途径。在此，我们制备了一种直接 Z 型光催化系统 Ti ³⁺缺陷型 TiO ₂ /CdS 纳米花，以提高 CO ₂还原生成 C1-C3 产物的能力。首先，使用TiB ₂前体制备纳米花状TiO ₂ (NF-TiO ₂ ) ，以构建Ti ³⁺缺陷。然后，通过TiO ₂ /Cd-MOF的硫化构建NF-TiO ₂ /CdS异质结。重要的是，最佳异质结光催化剂 NF-TiO₂ /CdS _0.6不仅对CO和CH ₄，而且对C2-C3烃类都表现出高度促进的CO _{2还原活性。}CO和CH ₄的累积产率分别为1007.0 μmol/g和83.5 μmol/g（2.5 h），C2-C3烃的产率为55.3 μmol/g（2.5 h）。C1-C3 产物的这种提高产率归因于大量 Ti ³⁺缺陷的协同效应，这些缺陷增加了 CO _{2的吸附和活化}，提供足够活性位点的大表面积，以及具有良好紧密接触界面的直接Z型异质结，可有效分离电荷载流子并以强还原性积累电子。此外，进行了羟基自由基的光致发光分析，为直接 Z 型机制提供了证据。该工作为构建基于 TiO ₂的直接 Z 型光催化体系提供了一种简便的方法，以提高光催化 CO ₂还原的性能。