塔菲尔方程
化学
催化作用
电解质
电化学
电荷转移系数
吸附
分压
电极
氧气
相(物质)
分析化学(期刊)
反应速率常数
电极电位
无机化学
物理化学
色谱法
循环伏安法
动力学
有机化学
物理
量子力学
作者
Nuttapol Limjeerajarus,Tatsunori Yanagimoto,Takahisa Yamamoto,Hidenori Ohashi,Taichi Ito,Takeo Yamaguchi
出处
期刊:Journal of Chemical Engineering of Japan
[The Society of Chemical Engineers Japan]
日期:2009-01-01
卷期号:42 (1): 39-46
被引量:13
摘要
The dependence of the oxygen reduction reaction (ORR) activity of Pt/C catalysts used in actual polymer electrolyte fuel cell membrane electrode assemblies (PEFC MEAs) on cell temperature, O2 partial pressure and catalyst loading has been investigated. Based on physical chemistry and electrochemistry points of view, the charge transfer coefficient (α) was demonstrated to vary with potential over a narrow range of 0.5–0.6. The double Tafel slope occurring at potentials above 0.8 V vs. RHE was considered to be caused by the effect of adsorption or reaction of oxygen-containing species sourced by water. As a result, the α was assumed constant at 0.5 irrespective of the potential, and used in the estimation of the ORR activity [A/cm2-Pt]. The ORR activity was observed to increase linearly with increasing temperature. It was also found to be dependent on O2 partial pressure (considered as O2 concentration) until it reached a plateau at an O2 concentration of 40%, and then remained almost constant. This finding implies that in gas-phase PEFC MEAs, adsorption of O2 as a reactant can influence and govern the electrochemical reaction. In addition, the ORR activity is demonstrated to be independent of the Pt/C ratio of the catalyst not only for Pt plate electrodes in liquid-phase systems, but also for MEA electrodes in the gas-phase system of actual single-cell PEFCs. The ORR activity was found to be almost constant at 2.6 × 10–6 A/cm2-Pt at 60°C for Pt/C ratios from 19.3 to 55.8 wt%.
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