制备方法对PtMo/C催化剂上CO电催化氧化性能的影响

用化学还原法、胶体法和Adams法制备了PtMo/C电催化剂, 对其物理化学性质及其在CO电氧化反应中的催化性能进行了对比研究. TEM和XRD测试结果表明, 胶体法制备的催化剂颗粒在载体炭上均匀分布, 颗粒粒径约5 nm；由化学还原法制备的颗粒尺寸较大, 而Adams法制备的颗粒尺寸达数十纳米, 并有严重的团聚现象. CO消除伏安法测试结果表明, 三种制备方法中胶体法制备的PtMo/C催化剂具有最高的电化学表面积和电催化活性. 与常用的Pt/C催化剂相比, PtMo/C催化剂中Pt上弱吸附态CO的电氧化均得到了促进, 而强吸附态CO则不受影响. 这些结果表明PtMo颗粒的尺寸分布和在载体上的分散状况是影响PtMo/C催化剂电催化性能的主要因素. 胶体法制备的PtMo/C与常用的PtRu/C相比, 电化学表面积虽然较低, 但在低电势下CO的起始氧化电势只有0.15 V, 而且在0.15～0.5０ V之间发生电氧化的CO达到其总量的1/3.

Electrooxidation of CO Adsorbed on PtMo/C Catalyst: Effect of Catalyst Preparation

PtMo/C electrocatalysts were prepared by three different preparation methods, namely 1) chemical reduction with oxalic acid, 2) colloidal precursor, and 3) Adams method respectively. TEM, XRD and CO-stripping in 0.5 mol•L-1 H2SO4 solution were performed to characterize the particle size distribution and electrocatalytic property of the prepared samples. PtMo particles from the colloidal preparation were ca. 5 nm in sizes and were well dispersed on the carbon support. The preparation by Adams method produced aggregated larger PtMo particles with sizes up to tens of nanometers. The sizes and morphology of PtMo particles from the chemical reduction method were found in between those from the colloidal preparation and the Adams method. The electro- oxidation of CO adsorbed on all of the three PtMo/C catalysts showed two distinct peaks, one at very low potential (ca. 0.15 V) and the other at a potential (ca. 0.77 V) very close to that over the conventional Pt/C catalyst. Moreover, the PtMo/C catalyst obtained from the colloidal preparation exhibited, among the three catalysts of this study, the highest electrocatalytic activity for the oxidation of CO. Although the electrochemical surface area of this PtMo/C catalyst was lower in comparison with the conventional PtRu/C catalyst, the removal percentage of CO at low oxidation potentials(0.15～0.50 V) was found to be much higher. Therefore, the presence of Mo component in the catalysts promoted the electro-oxidation of weakly adsorbed CO, whereas it showed little effect on the oxidation of strongly adsorbed CO.