在酸碱性介质中具有增强的表面微观结构敏感性的氧析出催化活性的铱-钯纳米合金研究(英文)

Ir-Pd nanoalloys with enhanced surface-microstructure-sensitive catalytic activity for oxygen evolution reaction in acidic and alkaline media

近年来铱基催化剂已经在一系列电催化反应中被广泛研究,氧析出反应(OER)是其中最突出的代表.研究不同p H介质中表面微观结构敏感的催化活性对于开发高效电催化剂及其反应机理研究具有重要意义.本文作者通过简单的一步溶剂热法合成了纳米空心球(NHSs),纳米线(NWs)和纳米四面体(NTs)等形貌可调的Ir-Pd合金纳米晶.通过电化学研究表明,Ir-Pd合金纳米催化剂在酸性和碱性介质中的OER活性增强表现出表面微结构敏感性.Ir-Pd NWs和NTs在酸性和碱性介质中0.25 V过电势下表现出商业Ir/C催化剂五倍以上的质量活性.XPS结果表明,在Ir-Pd纳米催化剂表面缺陷位置产生的Ir(VI)物种可能是反应中的一种关键中间体.在酸性介质中,Ir-Pd纳米催化剂的比活性与Ir-Pd纳米催化剂表面粗糙度呈正相关,即NWs>NHSs>NTs.而碱性介质中由于位于表面缺陷位点的Ir O2-4物种快速分解阻碍了Ir(VI)物种的形成,改变了Ir-Pd纳米催化剂的OER活性顺序.

Ir-based dectrocatalysts have been system- atically studied for a variety of applications, among which the electrocatalysis for oxygen evolution reaction （OER） is one of the most prominent. The investigation on surface-micro- structure-sensitive catalytic activity in different pH media is of great significance for developing efficient electrocatalysts and corresponding mechanism research. Herein, shape-tunable Ir- Pd alloy nanocrystals, including nano-hollow-spheres （NHSs）, nanowires （NWs）, and nanotetrahedrons （NTs）, are synthe- sized via a facile one-pot solvothermal method, Electro- chemical studies show that the OER activity of the Ir-Pd alloy nanocatalysts exhibits surface-microstructure-sensitive en- hancement in acidic and alkaline media. Ir-Pd NWs and NTs show more than five times higher mass activity than com- mercial Ir/C catalyst at an overpotential of 0.25 V in acidic and alkaline media. Post-XPS analyses reveal that surface Ir（VI） oxide generated at surface defective sites of Ir-Pd nanocata- lysts is a possible key intermediate for OER. In acidic medium, the specific activity of Ir-Pd nanocatalysts has a positive cor- relation with the surface roughness of NWs 〉 NHSs 〉 NTs. However, the strong dissociation of surface Ir（VI） species （IrO42-） at surface defective sites is a possible obstacle for the formation of Ir（VI） oxide, which reverses the activity sequence for OER in alkaline medium.