Photocatalytic reduction is a promising approach to detoxifying carcinogenic Cr(VI) in water. Herein, CdS-sensitized Cs₃PW₁₂O₄₀ composites were fabricated by electrostatic self-assembly followed by hydrothermal post-treatment strategy. The composite with 28.6 wt% CdS loading (CdS/CsPW) was characterized by XRD, FT-IR, SEM/TEM, EDX, UV-vis DRS, XPS, potentiometric titration, and N₂ adsorption. The catalytic activity was evaluated by reducing Cr(VI) in the presence of EDTA under UV and visible light irradiation. The results revealed that CdS/CsPW had good photocatalytic reduction performance for Cr(VI) degradation under both UV and visible light illumination. After four-time repetitive use, ~ 93% of catalytic activity still remained. The photocatalytic reduction of Cr(VI) under visible light irradiation followed pseudo-first-order kinetics; the decreasing solution pH and initial Cr(VI) concentration, and increasing catalyst dosage and EDTA concentration were beneficial to Cr(VI) photoreduction. XPS analyses further indicated that the Cr(VI) adsorbed on surface of the catalyst was also reduced to Cr(III), and CdS and Cs₃PW₁₂O₄₀ existed strong interaction. Meanwhile, the photoelectrons in CdS could migrate to Cs₃PW₁₂O₄₀. Further, PL results verified CdS/CsPW heterostructure effectively suppressed the photogenerated electron-hole recombination. Based on experimental results, the mechanisms for Cr(VI) photoreduction by the prepared catalyst were proposed. This work may provide an attractive avenue to construct the efficient photocatalyst using polyoxometalates for environmental remediation.

中文翻译：

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静电自组装辅助CdS / Cs 3 PW 12 O 40杂化物的光催化还原Cr（VI）

光催化还原是将水中致癌的六价铬（VI）解毒的一种有前途的方法。本文通过静电自组装，水热后处理策略制备了CdS敏化的Cs ₃ PW ₁₂ O ₄₀复合材料。通过XRD，FT-IR，SEM / TEM，EDX，UV-vis DRS，XPS，电位滴定和N ₂表征具有28.6 wt％CdS负载量（CdS / CsPW）的复合材料吸附。通过在紫外线和可见光照射下在EDTA存在下还原Cr（VI）来评估催化活性。结果表明，CdS / CsPW在紫外和可见光照射下均具有良好的光催化还原Cr（VI）的性能。重复使用四次后，仍保留约93％的催化活性。Cr（VI）在可见光照射下的光催化还原遵循拟一级动力学；降低溶液的pH值和初始Cr（VI）浓度，以及增加催化剂用量和EDTA浓度均有助于Cr（VI）的光还原。XPS分析进一步表明，吸附在催化剂表面的Cr（VI）也被还原为Cr（III），CdS和Cs ₃ PW ₁₂ O ₄₀存在强烈的互动。同时，CdS中的光电子可以迁移至Cs ₃ PW ₁₂ O ₄₀。此外，PL结果验证了CdS / CsPW异质结构有效地抑制了光生电子-空穴复合。根据实验结果，提出了制备的催化剂对Cr（VI）光还原的机理。这项工作可能为使用多金属氧酸盐进行环境修复来构建高效的光催化剂提供有吸引力的途径。