钯纳米晶体在电催化甲酸氧化反应中的形貌效应

本文基于课题组前期工作,选用适当的金属前驱物、还原剂、稳定剂和保护剂,通过调控氧化刻蚀和反应动力学等,成功合成了形貌和尺寸均不相同的Pd纳米晶.经过认真的纳米粒子清洗和电极修饰组装,考察了它们在电催化甲酸氧化反应中的形貌与性能的关系.研究结果表明,Pd纳米晶样品的最大电流密度以纳米八面体（nanooctahedra）、纳米线（nanowires）、纳米立方体（nanocubes）、纳米瓜子（nanotapers）、凹面纳米立方体（concave nanocubes）的顺序递增,催化甲酸氧化反应的起始氧化电位均小于0.2V.研究结果印证了Pd纳米晶催化甲酸氧化反应的催化性能在尺寸效应上主要受活性表面积的影响,扣除表面积效应后的催化性能与其尺寸没有明确关系.该系列Pd纳米晶的催化性能主要取决于其表面结构,得出Pd纳米晶催化甲酸氧化反应遵循{111}晶面〈{100}晶面〈高指数晶面的性能活性顺序.综合最大电流密度和最小操作电位因素发现,Pd凹面纳米立方体和Pd纳米瓜子具有相对较好的商用价值.

Structural effects of palladium nanocrystal electrodes on electrocatalytic oxidation reaction of formic acid

Palladium nanocrystals with various shapes and sizes were controllably synthesized by altering oxidative etching and reaction kinetics in the presence of appropriate metal precursors, reducing agents, stabilizers and capping agents, based on our previous works. Upon cleaning nanoparticles and assembling them onto electrodes, we systematically investigated the relationship between nanocrystal structures and catalytic performance in the oxidation of formic acid. It demonstrates that the maximum current densities of Pd nanocrystals increase in the order of nanoctahedra 〈 nanowires 〈 nanocubes 〈 nanotapers 〈 concave nanocubes. The onset potentials of all the samples are below 0.2 V. The results prove that the electrocatalytic performance of Pd nanocrystals is not significantly dependent on their sizes after normalized by active surface area. Instead, the catalytic activity is mainly determined by surface structures： the activities of various Pd facets in the oxidation of formic acid should be in the order of { 111 } 〈 { 100} 〈 high-index facets. Among various Pd nanostructures, concave nanocubes and nanotapers exhibit much better electrocatalytic performance.