磷酸燃料电池催化剂在运行中的形态变化

运用电化学方法测定了Pt/C催化剂在磷酸中不同时效阶段的电化学活性面积,同时采用XRD/TEM分析了Pt/C催化剂在时效过程中尺寸的变化,并运用分光光度法测量电极所在的磷酸中铂的含量,考察了铂/碳电极在不同情况下的溶解情况.结果表明:催化剂在时效过程中,随着时间的增加电化学活性面积逐渐减小,而Pt/C催化剂的粒径随着时间的增加逐渐增加;在开路电位下,催化剂的溶解量随时间的增加而增大,而催化剂在阴极极化下不发生溶解.分析讨论了碳载铂颗粒的增大机理和不同状态下铂的溶解机理.

The Agglomeration and Dissolution of Pt/C Catalyst in Phosphoric Acid

The effects of the crystallite size and the dissolution on the electrocatalytic behavior of carbon-supported platinum ageing in phosphoric acid are investigated by using XRD/TEM and elec-trochemical measurement.The distribution of crystallite size of Pt tends to shift to right with increasing ageing time,meanwhile the dissolution of Pt takes place under open circuit potential but not under cathodic polarization.Result shows that the decrease of electrochemical surface areas of Pt/C catalyst is responsible for the agglomeration and dissolution of platinum crystallites.The agglomeration of Pt crystallite can be explained by the migration and coalescence growth mechanism because there is no potential effect during the growth of Pt crystallite.The mechanism of the agglomeration and the dissolution of carbon-supported platinum are discussed.