We investigate the effects of the carbon supports on the Pt distribution, ionomer coverage and cathode performance of carbon-supported Pt catalysts, by using STEM observation, N2 adsorption analysis and electrochemical characterization. According to the STEM observation, the effective Pt surface area (S(e)Pt), which is determined by the location and size of the Pt particles on the supports, increases in the following order: c-Pt/CB < c-Pt/GCB < n-Pt/AB800 < n-Pt/AB250. The N2 adsorption analyses show that the Pt particles observed in the interior of the CB and AB800-supported Pt catalysts during the STEM observation could be ascribed to the hollow structures inside the carbon supports, which decrease their effective Pt surface areas. The S(e)Pt values are in good agreement with the cell performance in the high current density region. In spite of the highest Pt utilization (UPt) value (>90%) and uniform ionomer coverage, the c-Pt/CB catalyst shows the lowest cell performance due to the lower S(e)Pt value. On the other hand, the n-Pt/AB250 catalyst, for which all of the Pt particles exist only on the exterior surface, is found to be the most attractive in order to generate the large current densities required by actual fuel cell operation

Effects of microstructure of carbon supports for platinum catalyst and of perfluorosulfonate‐ionomer (PFSI) distribution in the microstructure of the catalyst layer on the consequent performance of polymer‐electrolyte fuel cells, prepared by a new method based on the process of PFSI colloid formation, were investigated by electrochemical techniques, a mercury pore sizer, adsorption [Brunauer‐Emmett‐Teller and Barrett‐Joyner‐Halenda] methods, and CO adsorption. The microstructure of the catalyst layer and its effect on polymer‐electrolyte fuel cell performance were affected by the contents of PFSI and carbon supports. The PFSI were distributed in the distinctive pores of 0.04 to 1.00 μm. Pore volume and pore diameter were primarily affected by the carbon supports. Carbon supports had a large pore volume with pore diameters less than 8 nm on the surface of the primary particles. Polymer‐electrolyte fuel cell performance predominantly increased with the specific volume of pores covered with the PFSI in the catalyst layer and with a decrease of the specific volume of pores less than 8 nm without PFSI on the carbon surface.

A new preparation method for the catalyst layer in the electrodes of a polymer electrolyte fuel cell, based on the process of preparing perfluorosulfonate‐ionomer (PFSI) colloid, was developed. In this method, both a good network of PFSI and uniformity of PFSIs on Pt particles were achieved with colloid formation of PFSI chains in the specific organic solvents. The applicable organic solvents had dielectric constants ranging from 3 to 10. The PFSI colloids were selectively adsorbed onto the carbon agglomerates with highly dispersed Pt particles on the surface, and a catalyst paste‐formation followed. Then the catalyst paste was spread over a carbon paper representing the gas diffusion layer, and two sheets of carbon paper with catalyst paste on them were hot pressed onto an ion‐exchange membrane from both sides. This simple preparation method provided high performance in fuel cells at low temperature (50°C).

The effects of carbon supports for platinum‐ruthenium (Pt‐Ru) catalysts on anode performance of direct methanol fuel cells (DMFC) were investigated. Good polarization characteristics of the methanol electrode were obtained for a Pt‐Ru catalyst supported on an acetylene black with high specific surface area and a pore size distribution in the range of 3 to 8 nm. The performance of the methanol electrode increased with the increase in pore volume for the pore size distribution of 3 to 8 nm. Analyses of various carbon blacks and supported catalysts were carried out with several techniques: adsorption (Brunauer‐Emmett‐Teller (BET) and Barrett‐Joyner‐Halenda (BJH) methods), adsorption, transmission electron microscope, and scanning electron microscope observations. The effects of the heat‐treating temperature, time, and atmosphere on the polarization curves of the methanol electrodes with the acetylene black were investigated. The heat‐treatment in air at 370°C improved not only methanol oxidation but the durability of the Pt‐Ru catalyst.