Effect of Pt Oxidation State on Methanol Oxidation Activity

Abstract

Pt catalysts supported on Vulcan XC-72 carbon were prepared by the NaBH 4 reduction of H 2 PtCl 6 in the presence of a carbon support. One of the catalysts was deliberately treated with H 2 O 2 after chemical reduction to alter the oxidation state of Pt and to promote methanol oxidation through more efficient water dissociation on the Pt sites. X-ray photoelectron spectroscopy confirmed that H 2 O 2 treatment resulted in a more oxidized Pt catalyst. The electrooxidation of methanol over treated and untreated Pt catalysts in acidic solutions at room temperature was investigated by cyclic voltammetry and chronoamperometry. Despite their design, the more oxidized Pt catalysts could not supply active oxygen capable of removing the reaction-inhibiting CO-like reaction intermediates. As a result the catalytic activity was still largely dependent on the Pt oxidation state with the more “metallic” catalyst showing higher methanol oxidation activity and more CO tolerance. ： 采用NaBH 4 还原法制备了 XC-72 碳黑负载的 Pt 电催化剂, 并在化学还原后用 H 2 O 2 处理部分催化剂以改变 Pt 的氧化状态, 以期改善 Pt 活性中心上水的离解而提高催化活性. X 射线光电子能谱结果表明, 经 H 2 O 2 处理的催化剂含有较多的氧化态 Pt. 通过循环伏安法和记时电流法考察了经处理和未经处理的催化剂在酸性条件下的甲醇氧化的催化活性. 结果表明, 经氧化法产生的含有较多氧化态 Pt 的催化剂并不能提供活性状态的氧以去除阻碍反应的 CO 中间体, 含有较多金属状态 Pt 的催化剂活性反而更高, 抗 CO 性能更佳. We prepared a Pt catalyst that was deliberately oxidized and compared it with a catalyst that was not oxidized for application in methanol oxidation. We found that the catalyst prepared by deliberate oxidation did not have high activity because of its inactive oxidation states.