Ag-Pd团簇助催化剂的可控制备及增强光催化CO2还原机理研究

The photocatalytic CO2 reduction into chemical fuels by utilizing solar energy shows the promising application foreground. However, traditional photocatalysts still exhibit some problems, such as low efficiency of conversion, and difficulty of recycling. This project will choose the typical visible-light-driven photocatalyst of CdS as a model compound and carry out a research on the photocatalytic CO2 reduction over Ag-Pd alloy-cluster/CdS thin film (denoted as Ag-Pd/CdS), which will be prepared by our “high-resolution mass-selective cluster beam facility” system. The regulation mechanism of Ag-Pd alloy-cluster toward surface electronic structure of CdS will be revealed by combining the theoretical calculation with experimental research, and the transport characters of photogenerated carriers will be discussed. By regulating surface sulfur vacancies and Ag-Pd alloy-cluster, the surface and interface structure of CdS thin film will be achieved to enhance adsorption ability of CO2 and potential for CO2 activation, and the corresponding activation mechanism of C=O bond will be revealed so as to achieve high activity and product selectivity of photocatalytic CO2 reduction. In addition, this project will provide a new method for the controllable preparation of noble metal alloy-cluster and then deposited on thin film. It is urgent to explore mechanism at molecular level for the improved photocatalytic CO2 reduction caused by synergistic effects of defect, component and size effects of Ag-Pd alloy-cluster. This work will also provide some experimental and scientific bases for the further construction of novel film photocatalysts for CO2 reduction with high efficiency.

太阳能光催化CO2还原为化学燃料具有广阔的应用前景，但传统光催化材料仍存在转化效率低、回收困难等问题。本项目选择经典可见光催化材料CdS作为模型，拟开展“高分辨质量选择团簇束流实验装置”可控制备Ag-Pd合金团簇沉积的CdS薄膜（Ag-Pd/CdS）应用于光催化CO2还原研究。结合理论计算和实验研究，揭示Ag-Pd合金团簇对CdS表面电子结构的调控机制，阐明光生载流子的输运特性。通过调控硫空位和Ag-Pd合金团簇，构建有利于CO2吸附和活化的表界面结构，揭示C=O键活化机理，以此实现高效光催化CO2还原路径和产物选择性。通过本研究，将提供一种可控制备的合金团簇沉积于薄膜新方法，在分子水平上阐明缺陷、贵金属合金团簇组分效应和尺寸效应协同增强光催化CO2还原性能机制，为开发高活性新型薄膜光催化CO2还原体系提供一定的实验基础和科学依据。

光催化材料在解决环境污染物和能源短缺方面问题正日益发挥重要作用。针对传统光催化材料光响应范围窄、光催化量子效率低等问题，有必要研制高活性、具有实用价值的可见光催化材料。本项目将Ag-Pd合金团簇的合金组分效应与团簇尺寸效应作用于ZnIn2S4（ZIS）材料，改善其光催化性能。主要研究内容和结果包括：采用化学还原法将Ag-Pd合金团簇与球状ZIS结合，通过优化Ag与Pd的摩尔比和Ag-Pd合金团簇的总负载量，最佳样品Ag0.25Pd0.75-ZIS在可见光下表现出最大的析氢速率。Ag0.25Pd0.75-ZIS样品光催化析氢活性的增强主要是由于双金属的协同效应，其表现如下。首先，通过负载Ag-Pd双金属合金形成的等离子体可以显著提高ZnIn2S4的光捕获能力。其次，Ag-Pd合金与ZIS界面之间形成的最优肖特基势垒高度有利于延长电子-空穴对的寿命并且促进电荷载流子的分离，从而提高光催化析氢效率。密度泛函理论（DFT）分析表明，在Pd0.75Ag0.25合金上H*的吸附能无限接近于零。因此，在理论上这样的H*具有最高的产氢活性，这种现象也与实验结果相一致。结合理论计算与实验结果，提出并验证了光催化机理。课题组又选择用Ni/Pd双金属与ZIS结合形成NiPd双金属/ZIS肖特基异质结构，结果表明NiPd双金属负载对增强光捕获能力、促进电荷载流子（电子和空穴）分离和促进光生电子迁移起到重要的作用，最终导致NiPd-ZIS光催化性能提高。另外，在完成研究目标前提下，还做了一些拓展研究，揭示了其光催化反应机理，开发了一系列新型高效可见光响应光催化剂。总之，本项目完成了预期研究目标，获得了大量宝贵经验和重要研究结果，可有效推动对光催化剂的理性修饰和对光催化反应机理的深刻认识。相关研究成果以第一作者（或通讯作者）发表SCI学术论文13篇，其中SCI一区论文7篇，高被引论文2篇。获得国家授权发明专利2件，荣获中国仪器仪表学会科学技术进步奖（二等奖）1次。