钼酸盐的电化学行为及其对甲醇氧化的催化作用

Electrochemical behavior of molybdate and its catalysis on the methanol oxidation

用循环伏安和线性电位扫描法研究了硫酸溶液中多晶铂电极上Na2 MoO4 的电化学行为及其对甲醇氧化的催化作用。结果表明 ,Na2 MoO4 在 3 .7mol/LH2 SO4 溶液中 ,一步还原生成不稳定的有色产物钼青铜 (HxMoO3) ,还原峰电位为0 .0V(相对于饱和甘汞电极 ) ,并有一对应氧化峰。多晶铂电极因钼酸盐的还原与氧化而得以修饰。这种修饰电极对甲醇的氧化有很强的催化作用。修饰多晶铂电极上甲醇的氧化电流远大于未修饰多晶铂上的氧化电流。在 1mol/LCH3OH + 0 .0 5mol/LNa2 MoO4 + 3 .7mol/LH2 SO4 溶液中 ,正向扫描电位超过还原钼酸盐氧化峰电位后 ,氧化电流大于相应甲醇和钼酸盐硫酸溶液中氧化电流和的 2倍以上。甲醇在未修饰多晶铂电极上由于吸附一氧化碳中毒引起的电流下降现象 ,也因还原钼酸盐的修饰作用而消失。

The electrochemical behavior of molybdates on a platinum electrode and the catalysis of methanol oxidation on the platinum electrode with reduced molybdates in H 2SO 4 solution were investigated by linear sweep voltammetry and cyclic voltammetry. The results show that molybdates are reduced to an unstable colorized product (hydrogen molybdenum bronze, H xMoO 3) in H 2SO 4 solution, which is adsorbed on platinum and the reduction peak potential is 0.0 V (vs. SCE), and the reduced molybdates can be reoxidized. With the reduction of molybdates and the oxidation of the reduced molybdates, the platinum electrode is modified. There is a strong catalysis of methanol oxidation on such a modified platinum electrode. In 1 mol/L CH 3OH+0.05 mol/L Na 2MoO 4+3 7 mol/L H 2SO 4 solution, the catalysis of methanol oxidation takes place after the peak potential of reduced molybdates. The catalytic current is higher than twice of the sum of the oxidation currents in 1 mol/L CH 3OH+3.7 mol/L H 2SO 4 solution and in 0.05 mol/L Na 2MoO 4+3.7 mol/L H 2SO 4 solution. There is no current decrease on the modified platinum electrode, which occurs due to the poisoning of adsorbed CO on a platinum electrode.