Pt电极表面有机小分子毒化中间体CO覆盖度的有效调控

An efficient method in manipulating CO coverage dissociated from small organic molecules on the Pt electrode surface

燃料电池因高能量利用率和环境友好等优点成为最有发展前途的一种能量利用方式,但有机小分子中间产物(CO)导致催化剂中毒一直是困扰燃料电池阳极催化剂的重要问题.本文利用可控电位高效更换溶液的电解池研究了不同电位下甲醛(HCHO)在Pt电极上解离CO的过程.实验结果表明,随着电位正移,HCHO在Pt上产生的CO覆盖度由.0.2 V的71%逐渐下降到0.25 V的60%.0.3 V起覆盖度急剧下降,在0.35 V时控电位的覆盖度仅有8%,远小于开路电位(ocp)下的64%.这预示着可以利用CO覆盖度的区别,提出一种新的电极操作方法以降低CO对电极的毒化.HCHO验证实验表明,控电位0.35 V时加入甲醛稳定300 s后,起始氧化电流为3×10^(-4 )A,接近峰值电流4×10^(-4) A,远大于ocp实验的3×10^(-5) A.控制工作电极电位0.35 V时加入甲醛。

Fuel cells are environmentally friendly energy systems with high energy efficiency, which are expected to play important roles in the sustainable society. However, CO-caused poisoning catalysts have been important problems in fuel cells, which hinder the practical applications of fuel cells. In this study, we studied the process of HCHO dissociation on the Pt electrode under different potentials using the electrochemical cell which can control the potential and replace the solution efficiently. The experimental results showed that with the positive shift of potential, the CO coverage on Pt due to the dissociation of HCHO slightly decreases from 71% at -0.2 V to 60% at 0.25 V. A sharp decline of the coverage of CO appears at 0.3 V. The coverage of CO is only 8%, which is far less than 64% at the open-circuit potential （ocp）. The experimental results indicated that we can apply different control potential to manipulate the CO coverage and thus propose a new method of operation to reduce the CO poisoning. Verification experiments in formaldehyde showed that the initial oxidation current was 3×10^-4 A, close to the peak current of 4×10^-4 A and far more than the current of 3×10^-5 A at the ocp experiment, after the addition of formaldehyde with potential control at 0.35 V for 300 s. Adding formaldehyde with potential control at 0.35 V can reduce the poisoning effect of CO on the catalyst effectively. This result may practically be applied in the commercial fuel cells.