银/含氧酸银等离子共振催化剂可见光催化还原二氧化碳的催化行为及反应机理

The development of visible light driven catalysts for effective photocatalytic reduction of CO2 has scientific significance and application value to solve the problem of environmental pollution and energy crisis. Considering the low quantum yield and turnover number of traditional semiconcuctors in photocatalytic reduction of CO2 under visible light irradiation, this project aims at synthesizing plasmonic Ag/silver oxysalt materials for effectively photoreducing the CO2 in both solid-liquid and solid-gas reaction systems. To the best of our knowledge, the subject has rarely been studied in depth to date. By adjusting the preparing variables, the effective methods for synthesizing Ag/silver oxysalt photocatalysts are presented with the help of catalyst characterization, and the correlation between the physicochemical properties of the catalysts and the preparing methods is established. Moreover, the dependence of the activity, selectivity and stability during CO2 photoreduction and the charge transfer in materials on the physical-chemical properties of catalysts such as composition, crystal structure, morphology and spatial structure is explored. Two types of photocatalytic systems, including solid-liquid and solid-gas mode, are used to optimize the major operating parameters, in an attempt to increase the quantum yield and energy returned on energy invested of photocatalytic reduction of CO2 under visible light irridiation. Meanwhile, the interface performance and the reaction mechanism of photocatalytic reduction of CO2 in various reaction systems are investigated. The project, with significant academic value and potential application, will not only provide an innovative approach for the design and preparation of new photocatalytic materials, but also contribute to the cross-integration of the disciplines of chemistry, materials, environment and energy.

研制开发高效可见光驱动催化剂进行CO2光催化还原对解决环境污染和能源短缺问题具有重要的科学意义和应用价值。本项目旨在合成新型银/含氧酸银等离子共振催化剂，并将其应用于液/固及气/固体系中CO2的高效还原，该项目的深入研究迄今尚属空白。通过调节制备参数并结合各种催化剂表征手段，建立银/含氧酸银等离子共振催化材料的有效合成方法，探明制备方法与催化剂物理化学性质之间的关系；调控催化剂的组成、晶型、结构、形貌等物性，确定其与材料内电荷传递过程及光催化还原CO2的活性，选择性，寿命之间的关系；构建气/固和液/固光催化体系，优化工艺参数，以期提高目标产物生成的量子效率和能量效率，并探明不同反应体系中可见光催化还原CO2过程中的界面过程及CO2的还原途径。本项目不仅为制备新型光催化材料提供一条崭新的途径，也可促进化学、材料、环境和能源等学科的交叉融合，有重要的学术意义和潜在的应用价值。

化石燃料的大量燃烧会引起大气中CO2含量的不断上升从而导致“全球变暖”。降低大气中CO2含量并将其转化成可以利用的碳源值得深入研究。光催化还原CO2利用清洁、易得且取之不尽用之不竭的太阳能，为减排CO2并解决能源短缺问题提供了一个潜在方法。高性能的等离子体光催化作为一个非常有应用前景的光催化剂技术近年来成为研究焦点，它需要在半导体表面分散贵金属纳米颗粒（主要是Au和Ag）以形成金属-半导体复合光催化剂，通过表面电子振荡导致的局域表面等离子体共振（LSPR）强化可见光吸收。本项目研究了一系列新型等离子体光催化剂，包括Ag/Ag3PO4，Ag/AgIO3，Ag/Ag2SO3和Ag/Ag2WO4等。通过X射线衍射（XRD）、X射线光电子能谱（XPS）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、能量色散X射线（EDX）、UV-Vis吸收光谱和Brunauer-Emmett-Teller（BET）比表面积测试，探明了光催化剂的物理化学性质并考察了其在可见光激发（λ>400nm）下光催化还原CO2的活性、选择性和稳定性。研究结果表明等离子体-半导体结构材料复合而成的等离子体光催化剂可作为可见光催化还原水蒸气饱和的CO2的有效催化剂，还原产物主要为CH3OH，CH4和CO等含碳物质，量子产率（QY）和能量投入产出比（EROEI）分别为0.126-0.436％和0.152-0.225％。此外，该类光催化剂在多次循环实验后仍保持高的可见光还原CO2稳定性。催化剂的高活性主要归因于半导体表面Ag纳米粒子在可见光辐照下的LSPR效应。能量传递包括激发电子的直接注入和共振能量转移导致半导体导带电子的强化，从而有利于CO2的还原；价带空穴同时作用于水的氧化。通过进一步提高活性、选择性和稳定性，本项目所研制的新型等离子体共振光催化剂有望应用于太阳光驱动的光催化还原CO2。