Keggin型钴取代杂多阴离子PW_(11)O_(39)Co(Ⅱ)(H_2O)^(5-)的电催化性能

Electrocatalytic Properties of the Keggin-Type Co(Ⅱ)-Substituted Heteropolyanion PW_(11)O_(39)Co(II)(H_2O)^(5-)

本文用循环伏安、交流阻抗等电化学方法研究了Keggin型钴取代杂多阴离子PW11O39Co(Ⅱ)(H2O)5-(PW11Co)的电化学性质及其对H2O2和甲醇阳极氧化的电催化作用,提出了PW11Co作为阳极媒质可能的电催化机理.结果表明,PW11Co除了2对可逆的W—O骨架峰之外,在1.367 V/1.266 V处还有1对准可逆的Co峰,对应于Co(Ⅱ)/Co(Ⅲ)电对的氧化还原响应.该电极过程有质子参与,其交换电流密度i0为5.7×10-6A·cm-2.在酸性条件下(pH 2.5),PW11Co对H2O2的阳极氧化具有明显的电催化活性,耦合甲醇的氧化可使甲醇的氧化速率显著提高.

The electrochemical properties of the Keggin-type Co（II）-substituted heteropolyanion PWI1039Co（II）（H20）s-（PWlICo）, as well as the electrocatalytic properties of PWllCo towards the anodic oxidations of H202 and CH3OH were studied using the electrochemical methods such as cyclic voltammetry and AC impedance spectroscopy in this paper. An electrocatalytic mechanism of PW.Co as an anodic medium was also proposed. It was found that PW11Co showed a pair of pseudo-reversible redox peaks at the potentials of 1.367 V/1.266 V, corresponding to the redox responses of the Co（II）/Co（III） couple, apart from two pairs of reversible W--O skeleton redox peaks. A proton was involved in the electrode process of the Co（II）/Co（III） couple with an exchange current density （io） of 5.7x106 A.cm-2. In particular, the couple exhibited a high electrocatalytic activity towards the anodic oxidation of H202 in an acidic solution ofpH 2.5, which can be coupled to catalyze the methanol oxidation.