Investigation of Impact of Carbon Surface Oxidation on Wettability of PEMFC Cathode Electrode
In order to elucidate the influence of platinum on carbon oxidation in more detail, carbon oxidation on Pt/C under potential dynamic model has been investigated. Four reactions were assigned as carbon oxidation reactions.
C + H2O → CO2 + 4H+ + 4e- (1)
C-C + H2O → C-COH + H+ + e- (2)
C-COH + H2O → C-COOH + 2H+ + 2e- (3)
C-COOH + Pt-OH → CO2 + Pt + COH + H+ + e- (4)
Carboxyl group and phenol group species were induced from graphite structure carbon on carbon surface through the electrochemical reactions with water.
High potential hold at 1.3V and potential cycling 0.1 V to 0.9 V were exposed to Pt/C catalyst under 0.1M H2SO4aq. in order to oxidize carbon surface. The carboxyl group and phenol group on carbon surface were measured before and after potential tests by Boehm method. Carbon groups were increased after 1.3V hold and potential cycling between 0.1 and 0.9V in Table 1. High potential hold caused high oxidation state carbon groups than lower potential cycling test. The increases in carbon groups on carbon surface is estimated to affect on the wettability on carbon surface and causes the suppress of PEFC performance.
Authors appreciated Dr. T. Abe and K. Miyazaki of Kyoto University for the discussion on this work.
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