甲醇阳极氧化Pt-Ru催化剂双中心机理动力学

根据文献报道的极化实验数据,回归出活化能值并修正了动力学参数,定量分析了吸附态甲醇Mad、COad、OHad三种中间产物的覆盖率,讨论了其在不同温度和甲醇浓度下与超电势的理论关系,并计算出基于吸附-反应动力学的极化曲线。结果表明,COad覆盖率CθO虽小,但其变化规律对动力学行为影响最大;超电势较小时速率控制步骤为吸附态甲醇的电化学分解,超电势较高时则转为甲醇在Pt上的活化吸附,中等超电势时为无速率控制步骤的过渡阶段。理论极化曲线与所报道的极化实验数据很好相符,但在高甲醇浓度及高超电势下出现偏差,这很可能是产物CO2气泡影响变大所致。

Dual Site Kinetics of Methanol Oxidation on Pt-Ru Anode

The kinetic parameters reported by Scott et al were modified and the activation energies are regressed by using experimental polarization data and the coverages of intermediate species involving adsorbed methanol(Mad),COad and OHad are quantitatively analyzed.Furthermore,the relationship between coverage and overpotential is discussed under different operation temperatures and methanol concentrations,then the theoretical polarization curve is calculated on the basis of adsorption-reaction kinetics.The results show that the small coverage of COad has significant influence on kinetic behaviors.The rate-determining step is the electro-decomposition of adsorbed methanol at low overpotential and changes to methanol activation adsorption on Pt site at high overpotential.A transition area exists without ratedetermining step at middle overpotential.The theoretical polarization curve gives good agreement with the experimental data,though with some deviation at high methanol concentration and high overptential possibly because of the increasing influence of the CO2 bubbles produced from the reaction.