甲醇在铂-氢钼青铜共沉积电极上的催化氧化

Electrocatalytic oxidation of methanol on co-deposited platinum and hydrogen molybdenum bronze electrodes

用循环伏安法在玻炭电极上制备了不同含量的铂电极和铂-氢钼青铜共沉积电极,研究了制备电极时的循环次数对制备电极的真实铂面积及甲醇氧化行为的影响。结果表明:单纯沉积铂电极的真实铂面积随着循环次数的增加而增加,并且沉积铂电极对甲醇的催化活性只取决于铂的真实面积;铂-氢钼青铜共沉积电极对甲醇氧化的催化能力与共沉积铂钼的比例有关,当制备电极所用的溶液中氯铂酸与钼酸钠的摩尔比为2!1时,共沉积电极的催化活性最高,此时甲醇在共沉积电极上的氧化峰电流是单纯铂电极的1.63倍。通过考察甲醇氧化峰电流对电极的铂真实表面积和沉积氢钼青铜量的依赖关系后发现,沉积氢钼青铜对铂的催化活性有双重作用。一是分散作用,沉积氢钼青铜使沉积铂更加分散,增大了铂的真实表面积;二是质子溢出效应,氢钼青铜通过不同质子含量的氧化还原电对,HyMO3/HxMO3(y<x<2),不断结合质子使铂表面的吸附中间体更易氧化。

Platinum and platinum-hydrogen molybdenum bronze electrodes with various contents of platinum and/or hydrogen molybdenum bronze were prepared on a glass carbon electrode, and the influence of cycle number for electrode preparation on the real surface area of platinum and the oxidation behaviors of methanol on the prepared electrodes were studied by cyclic voltammetry. The results show that real surface area of the prepared platinum electrodes increases with increasing cycle number for electrode preparation and the electrocatalytic activity of the electrodes toward methanol oxidation only depends on the real surface area of platinum. However, the electrocatalytic activity of platinum-hydrogen molybdenum bronze electrodes is related to the ratio of platinum and molybdenum. It reaches its maximum when the molar ratio of platinum and molybdenum in the solutions for the electrode preparation is 2 ： 1. In this case the oxidation peak current of methanol on the platinum-hydrogen molybdenum electrode is 1.63 times of that on the platinum electrode. Considering the dependence of the oxidation peak current of methanol on the real surface area and the ratio of platinum and molybdenum, it is found that there are two effects of hydrogen molybdenum bronze in the improvement of electrocatalytic activity of platinum： one is dispersing effect, the real surface area of platinum is increased by the co-deposition of platinum and hydrogen molybdenum; the other is proton spillover effect, the hydrogen molybdenum bronze continually accepts proton from the methanol oxidation on platinum by the oxidation and reduction of couple HyMO3/HyMO3 （y〈x〈2） and makes it easier for the oxidation of adsorbed intermediates on platinum.