Study Of PEMFC Electrodes Platinized By Pulse Electrodeposition

Proton exchange membrane fuel cell (PEMFC) is one of the most promising cells used for transportation and portable power sources for it has prominent merits such as high efficiency, cleanness and et al. However, the intolerable cost and poor catalysis of the catalyst Pt currently used in PEMFC, together with other technical problems, block PEMFC from commercialization. At present, most of work has been devoted to increase the utilization of platinum (Pt) catalysts and thus to lower the catalyst usage.In this paper, an uncatalyzed carbon electrode (UCE), on which a layer of Nafion-bonded carbon was dispersed in advance, was served as a substrate for electrodeposition. The platinized electrode by electrodeposition was assessed by the techniques of cyclic voltammetry (CV), X-ray diffraction (XRD), transfer electron microscopy (TEM),and spectrophotometry method.The preliminary results show:The electrodeposition of Pt is dependent to a large degree on the property of electrode/electrolyte interface inside the porous electrode. When the ratio of Nafion to carbon is 1:30 and carbon loadings keep at 0.2mg/cm2, the UCE is most suitable for electrodepositing Pt by a modulated pulse current deposition.By modulating the pulse parameters in electrodeposition, it is possible to controll the properties of Pt/C catalyst, such as the particle size, shape and distribution in the UCE; it is also feasible to restrain hydrogen evolution and thus leads to increase in current efficiency for Pt deposition, and the Pt utilization is higher than the tranditional Nafion-bond Pt/C catalyst. For instance: as the on-time and off-time were fixed at 300μs and 1200μs, respectively, and the total charge density was fixed at 0.3C/cm2, the electrode prepared at a peak current density of 67 mA/cm2 exhibits the best electrochemical performance, and meanwhile the particle size of the Pt deposits is as small as 12-17 nm. The Pt utilization of such an electrode is as high as 53.6%. The current efficiency for Pt deposition, in this case, is about 78%.The performance of electrode prepared by electrodeposition strongly depends on the pulse plating deposition parameter, which can be further optimized following the guidelines outlined in this paper.