The Study Of Pt/MWNTs And PtCo/C Electrodes For PEMFC Prepared With In-Situ Method

In this paper, the principles and the developments of proton exchange membrane fuel cell (PEMFC) were reviewed and the preparation methods of the PEMFC cathode were introduced. Then the functionalization process was studied during the electrode preparation by the in-situ ion exchange method, and the method of Pt deposition was improved. Meanwhile the electrode preparation method of PtCo/C catalyst was explored.Electrochemical and chemical dual-oxidation methods were employed to functionalize MWNTs prior to the preparation of the electrode. The composition of oxygen-containing groups on the surface of functionalized MWNTs was determined by X-ray photoelectron spectroscopy (XPS). Pt nanoparticles on the electrodes were characterized by energy dispersive X-ray (EDAX) and transmission electron microscopy (TEM). The performance of the electrodes was characterized by cyclic voltammetry and polarization curves for oxygen reduction reaction (ORR). More carboxylic acid groups generated on the surface of the electrode treated by electrochemical-chemical dual-oxidation (EC electrode), compared with the only electrochemical oxidation or chemical oxidation treatment. The resultant EC electrode had the most loading of Pt metal(16.4mass%), meanwhile Pt nanoparticles were highly dispersed on MWNTs. It exhibited the largest electrochemical surface area (280.3cm2) and the highest activity for ORR among the investigated electrodes. The increased electrochemical surface area and improved electrocatalytic activity could be attributed to the fact that more carboxylic acid groups were produced at the electroactive sites, which can lead to loading more electroactive Pt particles on the electrode in the following ion exchange process.Pt/C electrode was also prepared by the in-situ ion exchange method, and the Pt deposition method was improved. Electrochemical deposition method was employed to reduce Pt onto the support of C. Compared with the Hydrogen reduction, the electrochemical active surface of the electrode and the size of Pt particle are nearly the same. Moreover, the superiority of electrochemical deposition over Hydrogen reduchtion is higher efficiency, lower cost and more suitable for large-scale production.PtCo/C electrode was prepared by the ion-exchange method and the electrochemical deposition, The catalytic activity for Oxygen reduction reaction was improved. The reason may be that the unusual electronic structure ( d-band center position) and Pt-rich arrangement of near-surface layer weaken the interaction between the Pt surface atoms and nonreactive oxygenated (O, OH), which increases the number of active sites for O2 adsorption and improves the catalytic activity for ORR. So the in-situ method is promising in high acitive PEMFC electrode praperation.