制备过程中缓冲溶液对Pt-Ru/C电催化剂性能的影响

Influence of Buffer Solution on the Performance of Anodic Catalyst Pt-Ru/C During Preparation

采用浸渍还原法制备了Pt-Ru/C直接甲醇燃料电池阳极催化剂.为了提高催化剂的活性,使用乙酸钠和氢氧化钠缓冲溶液来调节反应溶液的pH值,考察了缓冲溶液对催化剂性能的影响;通过XRD和TEM技术对催化剂的晶体结构及微观形貌进行了分析;并利用玻碳电极测试了催化剂在0.5 mol/L CH3OH和0.5 mol/L H2SO4混合溶液中的循环伏安曲线和阶跃电位曲线,考察了催化剂对甲醇阳极催化氧化活性的影响.结果表明,用乙酸钠和氢氧化钠缓冲溶液调节反应溶液pH值所得催化剂的性能优于用NaOH调节反应溶液pH值所得的催化剂.缓冲溶液pH值对催化剂性能有较大影响,使用pH值为12的缓冲溶液所制备的催化剂性能最佳,Pt-Ru颗粒在碳载体上分散均匀,其最小粒径为4.2 nm.还原温度对缓冲溶液作用的发挥有一定影响,还原温度升高会使溶液的pH值下降,不利于缓冲溶液作用的发挥.

The Pt-Ru/C anodic catalysts for direct methanol fuel cells were prepared by the reduction method. pH values of the reductive solutions were adjusted by a buffer solution of NaOH and CH3COONa. The catalyst structure and micro-morphology were determined by X-ray diffraction and transmission electron microscopy, and the catalyst performance was examined by cyclic voltammetry and chronoamperometric curves with a glassy carbon working electrode in a solution of 0.5 mol/L CH3OH and 0.5 mol/L H2SO4. The performance of the catalyst prepared with buffer solution CH3COONa-NaOH was higher than that with NaOH solution. The best catalytic performance of the catalyst was obtained when the pH value of buffer solution was 12. Pt-Ru distributed homogeneously on carbon, and the smallest particle size was 4.2 nm. The effect of buffer solution was affected by temperature. The pH value was decreased with increasing temperature of reduction, and the catalyst activity was lowered. So the appropriate solution temperature should be kept at 80 ℃.