Electrocatalytic activity of catalyst-dispersed carbon electrode for phosphoric acid fuel cell(PAFC) as functions of surface group and catalyst particle size

Abstract

The present work is concerned with the electrocatalytic activity of catalyst-dispersed carbon electrode for phosphoric acid fuel cell(FAFC) as functions of surface group and catalyst particle size. In chapter Ⅲ, the effect of surface group on the electrocatalytic behaviour of 10 wt.% Pt-Fe-Co alloy-dispersed carbon (Pt-Fe-Co/C) electrode has been investigated as functions of applied potential and duration in 85% $H_3PO_4$ solution of 145℃, using Fourier transform-infrared(FT-IR) spectroscopy, combined with electrochemical experiments. It was shown from FT-IR spectra that surface group formed in this work mainly comprises carboxyl group and that the formation potential of carboxyl group, lies between 600 and 700 $mV_{RHE} From increase of charge transfer resistance (R_ct), and decrease of electrocatalytic activity for oxygen reduction with immersion time it is suggested that above the formation potential of carboxyl group, further formation of carboxyl group on the carbon support around the catalyst particle reduces active surface area of the catalyst particle with immersion time and hence enhances dead active area. On the other hand, below the formation potential, dissolution of carboxyl group previously formed on the carbon support raises active surface area of the catalyst particle and hence reduces dead active area. In the present study, relationship between electrocatalytic aspect of the electrode, and the amount of carblxyl group formed on the carbon support around the catalyst particle was well discussed with a schematic illustration. In chapter Ⅳ, the effect of platinum particle size on the loss in electrocatalytic activity of platinum dispersed carbon (Pt/C) electrode has been investigated in view of surface group formation in 85% $H_3PO_4$ solution at 145℃, Average particle size of platinum was controlled by heat treatment and then determined from X-ray diffractometry (XRD) analysis based on Scherrer equation and directly from Transmission electron mic...