Semiconductor photocatalytic reduction of carbon dioxide (CO2) is a promising approach to carbon neutrality, which can produce valuable chemicals such as CO, CH4, HCOOH, and CH3OH. Due to the high thermodynamic stability of linear CO2 molecules, the solar-CO2 conversion efficiency has been limited. To achieve high performance, a photocatalyst must meet a number of basic conditions, such as a suitable band structure, high charge transfer efficiency, and excellent surface reactivity. CDS is widely used for photocatalytic reduction of CO2 due to its narrow band gap, good visible light absorption, and appropriate redox potential. However, due to the rapid recombination of photogenerated electron-hole pairs and the fierce competition of hydrogen evolution reaction (HER), the CO2 conversion efficiency of CDS nanomaterials is severely limited. Therefore, reasonable modification of CDS materials is of great significance to improve their photocatalytic CO2 conversion performance.
Recently,Zhang Nan, Hunan UniversityQu ShuanglinwithXie XiuqiangCu-doped hollow CDS cubes (Cu HCCs) were prepared by gentle vulcanization of Cu-doped PBA precursors. The experimental results show that Cu is successfully incorporated into the bulk phase of the hollow CDS cube and forms a self-adjusting sulfur vacancy (VS) in response to the stress of Jahn-Teller distortion. At the same time, the researchers prepared hcc@cu catalyst samples doped onto the surface of CDS by adjusting the introduction sequence of Cu sources, and compared them to understand the effect of the spatial location of Cu species on catalytic performance. The results of photocatalytic reduction of CO2 in the aqueous phase showed that the optimized Co yield of Cu HCC was 144 mol g-1 h-1, which is 4 times and more than 5 times that of pure HCC and hcc@cu, respectively.
Based on experimental research and theoretical calculations, the researchers proposed a reasonable mechanism for the photocatalytic reduction of CO2 by Cu HCC-2: under photoexcitation, the electrons in the CDS valence band are excited to the conduction band, and during the diffusion of photogenerated charge carriers to the outermost surface, the dispersed Cu in the bulk phase of CDS effectively inhibits the recombination of photogenerated electron-hole pairs, and finally provides the high-concentration charge carriers required to promote the photocatalytic reduction of CO2. At the same time, the Cu in situ doping strategy shifted the center of the D band of Cu HCC-2 upward, which promoted the adsorption and activation of CO2 on Cu HCC-2. In addition, self-regulating VS in the bulk phase cannot effectively participate in the surface proton reduction reaction. These results allow the preferential reduction of the CO2 molecule by photogenerated electrons in Cu HCC-2, which is then converted to CO by a CoOh* intermediate. In this process, VS can effectively promote the conversion of COOH* intermediates to CO* intermediates. On the other hand, the surface Cu site can promote the desorption of CO*, which ultimately increases the yield of CO.
isolated cu sites in cds hollow nanocubes with doping-location-dependent performance for photocatalytic co2 reduction. acs catalysis, 2024. doi: 10.1021/acscatal.3c05412