含铜类新型多元硫（硒）化物的结构调控合成与光催化性能研究

The narrow band-gap multinary chalcogenides, represented by the copper contained ternary and quaternary sulfides and selenides, become the research trend in the visible-light photocatalysis field due to their various kinds of advantages (e.g. direct and tunable band-gap, high absorption coefficients). However, the photocatalytic activity and photon-electron conversion efficiency of copper-contained multinary chalcogenides are still relatively low due to the fast recombination of the photoinduced mobile charge carriers (electrons and holes), indicating the most important scientific question that needs to be solved urgently in this field. The material composition has a great effect on their chemical/physical properties (e.g. band-gap structures), which consequently influence the photocatalytic activity. .The main task of this project lies in the exploration of structural regulation and synthesis of a series of copper-contained novel multinary sulfides and selenides (e.g. Cu-Ni-S, Cu-Co-Se Cu-Zn-Ni-S, Cu-Zn-Co-Se, Cu-Co-Mo-Se, etc.), where the cost-effective and low toxic metal elements (e.g. cobalt, nickel, molybdenum, etc.) are introduced into the crystalline structure of copper-contained multinary chalcogenides. The attempt is to introduce the doping energy levels and crystal lattice defects into such novel structures to improve the photocatalytic activity in essence. The appropriate characterization methods and instruments, such as XRD, XPS, SEM and TEM (incl. HRTEM, SAED, TEM dark-field EDS line-scan and mapping), are employed to analyze the element composition and valence state, crystalline structure, particle size and morphology for the as-synthesized nanocrystals. The Rietveld refinement is adopted for the analysis of crystalline structure. The photo-absorption properties and visible-light-induced photocatalytic activity will also be evaluated. The characterization/evaluation results can provide constructive feedback for the optimization of experiment design and reaction condition, in order to systematize the general approach for the synthesis of this novel compound series. The influence of material composition/structure on the photocatalytic activity will also be investigated to disclose the clear structure-property relationship in order to provide scientific guidance for the research field of multinary chalcogenides.

以三元、四元含铜硫（硒）化物为代表的窄带隙多元硫属化合物，以其诸多优势成为了可见光（光电）催化领域的研究趋势。但是，上述化合物中光生电子和空穴发生复合的速度过快，光催化活性依然较低，为该领域亟待解决的最重要科学问题。鉴于材料组成与结构对其光催化活性有着至关重要的影响，本课题尝试将廉价低毒的钴、镍、钼等元素构筑到含铜多元硫（硒）化物中，实现一系列新型多元硫（硒）化物（如Cu-Co-Se、Cu-Zn-Ni-S、Cu-Co-Mo-Se等）的结构调控与合成，尝试引入掺杂能级和晶格缺陷，旨在从本质上改善其光催化性能。通过表征获取并分析材料组成、元素价态、晶型结构、粒径及形貌等信息，并进行可见光光吸收和光催化活性评价。表征结果反馈指导实验设计，优化反应条件，探索该系列化合物的常规性合成路线。探索并掌握材料组成结构、价态、形貌、表面态与光催化性能之间的清晰构效关系，为多元硫（硒）化物领域的研究提供指导。

含有多元素的过渡金属硫族化合物以其诸多优势成为了光/电催化领域的研究热点。但是，开发高效的过渡金属硫（硒）化物催化剂用于长期稳定的光/电催化降解污染物、有机物选择性增值转化以及制氢反应等应用领域尚存挑战。并且，催化剂表面催化活性位点的精细化学结构以及客体分子的活化机理尚存争议。..针对上述问题，通过本项目的顺利实施，系统性地掌握了热注射法合成含铜类多元硫（硒）化物（含有Cu、Ni、Co、Zn、S、Se等元素）、含铜类硫（硒）化物异质结纳米材料的关键制备技术，实现了低维碳纳米材料上原位异质化生长含镍类硫（硒）化物纳米晶的一步热注射合成。所得到的硫（硒）化物纳米晶粒径均一，具有优异的分散性，绝大多数产物晶粒尺寸在20nm以内。..研究发现，含铜类三元硫化物CuNi2S4超细高分散纳米晶、含铜类Cu2S/CuS异质结材料具有优异的光催化降解污染物以及光催化产氢性能；含铜类Cu2Se/Co3Se4异质结、含镍类硫（硒）化物/碳纳米纤维（管）异质结材料对甲醇的电催化氧化具有高选择性和长期稳定性；Ni@Ni3S2/CNTs核壳异质结构催化剂具有优异的电催化降解有机污染物性能；同时上述阳极反应能够有效降低电解体系整体的能耗，从而促进了阴极析氢效率的显著提升。上述含铜类、含镍类硫（硒）化物纳米材料在环境净化、清洁能源获取、以及高附加值化学品合成等领域具有广阔的应用前景。..另外，本项目的实施过程中，采用XRD、SEM、TEM、EDS、XPS、in situ Raman，基于同步辐射的XAFS等技术，并结合DFT理论计算，对于纳米催化剂的晶型结构、元素价态、晶格缺陷、形貌及表面态与其光（电）催化性能之间的构效关系，反应路径，反应中间体表面吸脱附等反应机理进行了深入而系统的探索与研究。相关研究成果能够反馈指导催化剂的合理设计，为更复杂的催化剂结构和光（电）催化反应体系提供有价值的参考。