Department of Chemistry and Chemical Engineering, Chongqing University , Chongqing 400030, China.
Department of Chemistry, State University of New York at Binghamton , Binghamton, New York13902, United States.
ACS Appl Mater Interfaces. 2015 Nov 25;7(46):25906-13. doi: 10.1021/acsami.5b08478. Epub 2015 Nov 16.
The catalytic synergy of nanoalloy catalysts depends on the nanoscale size, composition, phase state, and surface properties. This report describes findings of an investigation of their roles in the enhancement of electrocatalytic activity of PdCu alloy nanoparticle catalysts for oxygen reduction reaction (ORR). Pd(n)Cu(100-n) nanoalloys with controlled composition and subtle differences in size and phase state were synthesized by two different wet chemical methods. Detailed electrochemical characterization was performed to determine the surface properties and the catalytic activities. The atomic-scale structures of these catalysts were also characterized by high-energy synchrotron X-ray diffraction coupled with atomic pair distribution function analysis. The electrocatalytic activity and stability were shown to depend on the size, composition, and phase structure. With Pd(n)Cu(100-n) catalysts from both methods, a maximum ORR activity was revealed at Pd/Cu ratio close to 50:50. Structurally, Pd50Cu50 nanoalloys feature a mixed phase consisting of chemically ordered (body-centered cubic type) and disordered (face-centered cubic type) domains. The phase-segregated structure is shown to change to a single phase upon electrochemical potential cycling in ORR condition. While the surface Cu dissolution occurred in PdCu catalysts from the two different synthesis methods, the PdCu with a single-phase character is found to exhibit a tendency of a much greater dissolution than that with the phase segregation. Analysis of the results, along theoretical modeling based on density functional theory calculation, has provided new insights for the correlation between the electrocatalytic activity and the catalyst structures.
纳米合金催化剂的催化协同作用取决于纳米尺度、组成、相态和表面性质。本报告描述了对其在增强 PdCu 合金纳米粒子催化剂对氧还原反应（ORR）的电催化活性中的作用的研究结果。通过两种不同的湿法化学方法合成了具有受控组成且在尺寸和相态上略有差异的 Pd(n)Cu(100-n)纳米合金。进行了详细的电化学表征以确定表面性质和催化活性。还通过高能同步加速器 X 射线衍射与原子对分布函数分析对这些催化剂的原子尺度结构进行了表征。电催化活性和稳定性取决于尺寸、组成和相结构。对于两种方法的 Pd(n)Cu(100-n)催化剂，在 Pd/Cu 比接近 50:50 时显示出最大的 ORR 活性。结构上，Pd50Cu50 纳米合金具有混合相，由化学有序（体心立方型）和无序（面心立方型）畴组成。相分离结构在 ORR 条件下电化学电位循环时显示出向单相转变的趋势。虽然来自两种不同合成方法的 PdCu 催化剂中发生了表面 Cu 溶解，但具有单相特征的 PdCu 比具有相分离的 PdCu 更易发生溶解。对结果的分析以及基于密度泛函理论计算的理论建模为电催化活性与催化剂结构之间的相关性提供了新的见解。
