Phosphoric Acid Absorption and Performance of Gas Diffusion Electrode

Abstract

The present study was directed towards investigating the relationship between the acid absorption of the catalyst layer and electrode performance and discussing the pores available for the cathode and anode reactions. The catalyst layer was formed on a porous carbon substrate by spreading a slurry consisting of a carbon‐supported platinum catalyst and PTFE dispersion. The nonionic surfactant contained in the dispersion enhances the acid absorption. Pores from 0.2 to 10 μm in diameter are available for the reactions.

Phosphoric acid distribution in the membrane electrode assembly of high temperature proton exchange membrane fuel cells

“…On the other hand, Pt loading in electrodes is still high in a system using liquid state electrolyte such as high temperature PEMFC and phosphoric acid fuel cells (PAFC) [20][21][22][23][24][25][26][27][28][29][30]. Because the liquid state PA cannot be fixed around catalyst, the maximum TPB and the optimum amount of electrolyte in electrodes are difficult to achieve.…”

Influence of the temperature of heat treatment on phosphoric acid fuel cell cathodes

“…The arrangement of the single cell was the same as those reported in the previous paper [15,16]. Acid absorption of catalyst layer was measured using an apparatus similar to that of Mori et al [6]. The electrode (9 cm 2) contacting with phosphoric acid was maintained at 120 ~ for a week in air.…”

“…This is the exact reason for the poor cell performance especially with hydrogen/air. Mori et al [6] reported that the acid occupation under 350 ~ is affected by the undecomposed Triton X-100. However, from our results, it is confirmed that Triton X-100 was decomposed or evaporated completely from the catalyst layer under 250 ~ because of the catalytic action of platinum (results 5 and 6).…”

“…Maoka [12] reported the influence of heat treatment temperature on electrochemical properties of a cathode by means of half-cell apparatus, and concluded that the inferiority of the low temperature treatment is caused by the fact that PTFE remains unmelted. He and several other investigators believe that the melting point of PTFE particle is about 327~ and this temperature is the beginning point of melting [6,12]. However, the melting point of virgin PTFE particle is 342~ [13,14] and not 327 ~ Once the polymer melts and is solidified, then upon remelting, it melts at the previously reported and widely accepted lower temperature of about 327~ [14].…”

“…Breault et al [1] selected 280~ to remove the surfactant, and Watanabe et al [5] also selected the same temperature in an inert gas. Mori et al [6] studied the influence of temperature from 320-370~ in air, and observed the increase of the acid absorption capability of the catalyst layer below 350 ~ They concluded that the residues of Triton X-100 enhanced acid absorption. Holtz et al [7] also gave warnings on surfactant remaining.…”