Rao Lu, Jiang Yan-Xia, Zhang Bin-Wei, Cai Yuan-Rong, Sun Shi-Gang
State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, P. R. China.
Phys Chem Chem Phys. 2014 Jul 21;16(27):13662-71. doi: 10.1039/c3cp55059a. Epub 2014 Mar 25.
Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.
首次采用以Br⁻为形状导向剂的改进多元醇法，直接合成了具有不同Pt和Rh原子比的负载在石墨烯上的立方PtRh合金（PtxRhy/GN）。该过程未使用如PVP等容易占据电催化剂活性位点且难以去除的表面封端剂。除Br⁻外，石墨烯是形成立方形状以及保持催化剂高分散性的关键因素。利用X射线衍射（XRD）、扫描电子显微镜（SEM）和透射电子显微镜（TEM）对这些电催化剂的结构和形貌进行了表征。结果表明，它们由均匀的立方PtRh合金组成。采用传统电化学方法，如循环伏安法和计时电流法，研究了PtxRhy/GN对乙醇电氧化的电催化性能。可以看出，所有原子比的PtxRhy/GN均表现出高催化活性，其中活性最高的组成为Pt : Rh = 9 : 1原子比。利用电化学原位傅里叶变换红外光谱（FTIR）在室温下酸性溶液中评估乙醇中C-C键的断裂情况，结果表明合金中的Rh可促进乙醇中C-C键的断裂，原子比为Pt : Rh = 1 : 1的合金催化剂在乙醇C-C键断裂方面表现出明显更好的性能，且对乙醇完全氧化为CO₂的活性增强具有比其他Pt和Rh比例的合金更高的选择性。研究表明，PtxRhy/GN电催化剂对乙醇氧化的高活性归因于合金的特定形状、两种金属元素的协同效应以及石墨烯载体。
