电化学去合金化Pt(Pd)-Cu对氧的电催化还原活性的研究

应用电化学去合金法制备了表面覆盖有Pt(Pd)原子层的Pt(Pd)-Cu合金催化剂.研究该催化剂在0.1mol.L-1HClO4酸性溶液中对氧气电化学还原的催化活性,并采用同步辐射反常X-射线衍射法(Anomalous X-ray Diffraction,AXRD)和表面X-射线散射法(Surface X-ray Scattering,SXS)从原子尺度研究了去合金化后催化剂的结构.分析对比纳米颗粒、薄膜和单晶3种不同形式的去合金化Pt-Cu的结构和催化活性以及Pt-Cu和Pd-Cu两种不同合金薄膜的结构和催化活性.结果表明,表面应力是影响催化剂催化活性的关键因素,而应力大小则与去合金化后所形成的表面Pt(Pd)层的厚度相关,材料尺寸和组成元素等都影响表面Pt(Pd)层的厚度.提出可利用调控材料表面的应力来设计高催化活性的催化剂.

Catalytic Activities of Electrochemically Dealloyed Pt(Pd)-Cu Catalysts for Oxygen Reduction Reaction

The electrochemically dealloyed Pt(Pd)-Cu catalysts were prepared by electrochemical dealloying of Cu3Pt(Pd) and their catalytic activities toward oxygen reduction reaction(ORR) were studied in 0.1 mol·L-1 HClO4 solution.The structural features of the dealloyed Pt(Pd)-Cu were revealed by synchrotron-based anomalous X-ray diffraction(AXRD) and surface X-ray scattering(SXS) at an atomic scale.We established a relationship between the structure and the catalytic activity by comparing the ORR activity and the structure of dealloyed Cu3Pt nanoparticles with similarly dealloyed Cu3Pt thin films and Cu3Pt(111).The enhancement in the activity of the dealloyed Pt(Pd)-Cu is mainly attributed to the strain change in the Pt(Pd) overlayer formed on the surface after dealloying.The strain is related to the thickness of Pt(Pd) overlayer,which is affected by the size of the material and the diffusion coefficient of the constituent element.The catalytic activity for ORR can be tuned by the strain in the surface layer of a catalyst.