摘要/Abstract

本工作为非Ti基光热协同材料研究，使用溶液沉淀法制备了ZnO/Zn₂GeO₄复合材料（Z/ZGO）应用于光热协同分解CO₂.使用透射电子显微镜（TEM）、X射线衍射技术（XRD）、紫外可见漫反射光谱（UV-Vis DRS）、X射线光电子能谱（XPS）等表征手段对材料的形貌、光响应以及氧空位对反应的影响进行研究.锌锗二元氧化物复合材料综合两种半导体的优势，形成异质结，扩展了材料光谱响应范围，提高了材料氧空位形成能力，使得CO产率提高至单纯ZnO样品的5.55倍，并具有较好的循环稳定性.对扩展光热协同催化材料体系，进一步深化光热协同反应机理以及提升反应产率具有一定的前瞻和指导作用.
关键词: CO₂分解, 氧空位, 光热协同反应, 异质结, Zn基氧化物
Using solar energy to split CO₂ can realize the conversion and storage of solar energy at the same time, and alleviate the carbon emissions caused by the transitional use of fossil energy. Solar energy based photo-thermochemical reaction is a promising method for the CO₂ splitting. To further study the photo-thermochemical reaction mechanism and explore the non-titanium-based catalytic materials, the ZnO/Zn₂GeO₄ composite material (Z/ZGO) was prepared by solution precipitation method and used for photo-thermochemical CO₂ splitting. Composite semiconductor combined the advantages of the two components which made CO production reach 5.55 times that of pure ZnO. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to illustrate the crystal structure and chemical composition of the samples. The XRD pattern found that the samples crystallized well, and no obvious crystal form changes occurred after the reaction. Using SEM to observe the samples before and after the reaction, the particle size did not increase significantly and no obvious sintering phenomenon was found, which indicated that the material has good reaction stability. Photoluminescence (PL), UV-visible diffuse reflectance spectra (UV-visible DRS) and Mott-Schottky plots were used to evaluate the material's light absorption characteristics and energy band position. The band gap of ZnO and Zn₂GeO₄ samples were 3.27 eV and 4.56 eV, respectively, and the heterojunction was formed in the Z/ZGO sample. The presence of ZnO extended the spectral response range of Zn₂GeO₄, and due to the migration of photogenerated electron-hole pairs (EHPs) to ZnO, the recombination of EHPs was reduced. XPS analyses were also used to investigate change of oxygen vacancies during the reaction. The O 1s XPS spectra of the samples in the three cases (Case A:before light irradiation, Case B:after light irradiation and Case C:after reaction) were analyzed and found that the signal of the oxygen near the vacancies increased after light irradiation and decreased after reaction, which may indicate that oxygen vacancies were formed after light irradiation then consumed by CO₂ in the reaction. The Zn₂GeO₄ sample showed the largest increase in oxygen vacancies signal after light irradiation, indicating that Zn₂GeO₄ had a strong ability to form oxygen vacancies. Zn₂GeO₄ improves the capacity of oxygen vacancies formation in the sample, and further improved the yield of photo-thermochemical CO₂ splitting reaction. As a result, Z/ZGO combined the advantages of ZnO in light response and Zn₂GeO₄ in oxygen vacancies formation and improved the CO₂ splitting yield. This research has a positive effect on expanding the photo-thermochemical material system and further deepening the photo-thermochemical reaction mechanism.
Key words: CO₂ splitting, oxygen vacancy, photo-thermochemical reaction, heterojunction, Zn-based oxide


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