Journal
ELECTROCHEMISTRY
Volume 79, Issue 5, Pages 381-387Publisher
ELECTROCHEMICAL SOC JAPAN
DOI: 10.5796/electrochemistry.79.381
Keywords
PEFC; Durability; Start/Stop Cycle; Nanocapsule Method
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Funding
- New Energy and Industrial Development Organization (NEDO) of Japan
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The objective of this research was to assess the feasibility of the use of highly corrosion resistant graphitized carbon (GC) as a support for Pt nanoparticles in polymer electrolyte fuel cells and to assess the role of the state of Pt dispersion in the maintenance of performance. Three types of 50 wt % Pt-loaded catalysts (commercial Pt/CB, Pt/GC and an in-house-prepared nanocapsule Pt/GC) were subjected to durability testing by means of a standard voltage step protocol (0.9 V <-> 1.3 V vs. RHE, holding 30 s at each voltage, 1 min for one cycle) at 65 degrees C with H-2 (anode) and N-2 (cathode), and ambient pressure (0.1 MPa). The durability was estimated on the basis of either 3000 potential cycles (commercial Pt/CB) or 10000 cycles (commercial Pt/GC and nanocapsule Pt/GC). The current-voltage curves were measured initially and after certain numbers of cycles N at 65 degrees C, 100% RH with H-2 and air. The electrochemically active surface area (ECA) decreased with increasing N, particularly the commercial Pt/CB, which underwent severe degradation in the cathode. In contrast, commercial Pt/GC and nanocapsule Pt/GC showed slow ECA degradation, due to the high corrosion resistance of GC. Furthermore, it was found that the decrease in cell performance was smaller for the nanocapsule Pt/GC compared to that for the commercial Pt/GC by 10 to 50 mV, because the Pt nanoparticles of the nanocapsule Pt/GC were well dispersed over the whole GC surface. We also examined the changes in the state of dispersion of the Pt nanoparticles by use of transmission electron microscopy (TEM).
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