钴掺杂氧化铈纳米粒子电催化性能研究

氧化铈的电子导电性较低、氧空位数量少, 难以单独用作为电催化剂。但是掺杂过渡金属或非金属元素可以提高氧化铈的CO催化能力, 同时在氧化物中掺杂钴可有效提高材料的电催化能力, 因此本工作开展了对钴掺杂的氧化铈电催化性能的研究。采用均相沉淀法制备了钴掺杂的氧化铈纳米粒子, 电化学测试发现当钴掺杂比例为20mol%时, 氧化铈纳米粒子对氧气还原反应(ORR)和氧气析出反应(OER)的综合催化能力最强。经过10 h的长时间催化作用, ORR、OER过程中的电流密度分别下降了20%、5%左右, 远优于贵金属和未掺杂氧化铈纳米粒子催化剂, 显示出良好的催化稳定性。拉曼光谱、阻抗图及XPS谱图等的测试分析表明钴掺杂后材料的电荷转移阻抗降低(电子导电性的提高)、氧活性物种和氧空位增加是氧化铈催化性能提高的主要原因。本工作通过钴掺杂大幅度提高了氧化铈的电催化性能, 同时为其它离子导体作为双功能电催化剂的使用提供了借鉴。

Electrocatalytic Activity of Cobalt Doped Ceria Nanoparticles

It is very difficult for single ceria to be used as an electrocatalyst because of its relatively poor electron conductivity and rare number of oxygen vacancy. Recently, it has been studied in the field of CO catalysis by doping transition metallic or non-metallic elements to improve the catalytic ability of ceria, while recent research has demonstrated that many oxides containing cobalt display better electrocatalytic activity. In this study cobalt doped ceria nanoparticles were prepared by homogeneous precipitation method. The electrochemical tests show that the optimum doping molar ratio is 20mol% for ORR and OER catalytic effect. After 10 hours of catalysis, the current density of ORR and OER decrease by about 20% and 5%, respectively, far below the corresponding values when noble metal and undoped cerium oxide nanoparticles were used as catalysts, and it indicated that the prepared catalyst owns good catalytic stability. In addition, XPS and other tests show that the decrease of charge transfer impedance (the improvement of electronic conductivity), the increase of active oxygen species, and the increased oxygen vacancies after doping are main reasons for improved catalytic performance. Therefore, doping cobalt greatly enhanced electrocatalytic properties of ceria nanoparticles are greatly enhanced by doping cobalt, providing guidence for other ionic conductors employed as bifunctional electrocatalysts.