电子及晶体结构改性调控单分散性MPd (M=Fe, Cu和Ag)纳米合金颗粒电催化脱氯研究

The threaten of the persistent chlorinated organic pollutants to human life makes it imperative to develop effective treatment technologies, of which the electrodechlorination technology shows the most promising due to its high efficiency, low equipment investment, easy maintenance and no secondary pollution. The key of this technology is to explore high-performance catalyst, and this project will focus on preparing monodisperse MPd bimetallic nanoparticles catalyst (M=Fe, Cu and Ag) for electrodechlorination of 2,4-dichlorophenol, where a higher utilization of the noble metal Pd could be achieved from the nano size and the monodispersity. By alloying with metal M of different lattice perameters and work functions, different electronic structures of Pd could be obtained, and the relationship between the structure change and catalytic perfomance was investigated. Modification of the crystal structure from face-centered cubic (fcc-) to face-centered tetragonal (fct-) was conducted and its relation with the catalyst durability was also studied. The mechanism study proceeds through reaction path analysis, hydrogen evolution performance evaluation, and the active hydrogen [H] characterization, hoping to unravel the role of electronic and crystal structure in tuning the dechlorination efficiency and then define the key parameter that control the catalyst performance. The whole project is expected to establish theoretical guidance for design of high-effective catalysts, and provide technical support for the development of the electrodechlorination technology.

含氯有机污染物的危害性使相应处理技术的开发变得迫切，电催化还原技术因脱氯反应连续高效，设备简单易控和无二次污染等特点而逐渐成为研究热点。高效催化剂的研发是该技术发展的关键，本项目致力于制备单分散性MPd纳米合金颗粒催化剂(M=Fe, Cu或Ag)，利用其较大的比表面积和可控的成分结构提升催化性能。MPd纳米颗粒采用高温油相法合成，通过改变温度，表面活性剂比例及还原剂种类等调控颗粒尺寸、成分、结构和分散度。通过与不同晶格参数和功函数的Fe、Cu和Ag形成合金，及颗粒内面心立方 (fcc-) 和面心四方 (fct-)晶体结构的转化，调控Pd电子和晶体结构，优化脱氯效率和催化剂稳定性；分析脱氯路径，产氢固氢性能及活性氢[H]角色，探究Pd电子及晶体结构调控脱氯效率机制。本项目的顺利实施可望获得一种性能较优的催化剂，同时建立新的催化剂设计和优化思路，推动电催化还原脱氯技术的发展。

氯代有机污染物的危害性使相应处理技术的研发变得迫切，电催化氢化还原脱氯技术因脱氯反应连续高效，设备简单易控和无二次污染等特点而逐渐成为研究热点。本项目以Pd基纳米颗粒为阴极催化剂来处理水体2,4-二氯苯酚污染物（2,4-DCP），研究脱氯机理，提出催化剂性能优化策略。本研究首先识别了电解水产生的吸附态原子氢是脱氯反应中唯一活性组分，阐明了其浓度随电压的演化规律及其与脱氯活性的关系；确定溶液pH可有效调控脱氯过程中脱氯反应和产氢气反应的竞争关系，优化脱氯效率和能量利用率，并确定pH的调节功能源于其可有效控制产氢速率及2,4-DCP的吸附行为；确定了脱氯产物苯酚的脱附是电催化脱氯反应的决速步骤，缓解苯酚毒化作用，加强2,4-DCP的有效吸附，是增强脱氯效率的有效路径；确定引入第二金属Ag可有效优化电催化脱氯过程中脱氯效率和能量利用率；探究确定Ag的调节功能源于其可调节Pd表面应力，优化2,4-DCP与产物苯酚在催化剂表面的吸附强度，增强Pd抗毒化效果；识别了脱氯反应路径及C-Cl键反应选择性，确定了羟基去质子化在2,4-DCP脱氯反应中的决定性作用；首次提出构建金属-半导体肖特基异质结电催化剂，通过肖特基异质结效应来调节Pd电子结构，缓解产物苯酚对催化剂的毒化作用。本项目的研究成果将对电催化氢化还原脱氯技术原理和关键反应步骤提供更清晰更深层次的解析，对如何调控脱氯效率、能量利用率和产物分布提供更经济有效的策略和手段，也将积极推进电催化氢化还原脱氯反应在环境污染控制和修复方面的应用；同时，本项目的研究内容也可为电催化氢化还原技术在处理其它水体污染物方面的研究提供理论参考，具有重要的科学意义和广泛的应用价值。