Platinum nanoparticles are used as electrocatalysts of polymer electrolyte fuel cells (PEFCs). Platinum particles become large during long-term operation of PEFCs and degrade the PEFC performance. This study investigated techniques for measuring platinum particle size from transmission electron microscopy images. Three types of measuring techniques, (1) particle outline, (2) detachment of coalescences, and (3) removing agglomerates, were adopted for agglomerated platinum particles. Detachment of coalescences (2) was found to be the most appropriate for a degraded electrocatalyst with complicated agglomerates of platinum particles for distinguishing coalescences of platinum particles that form agglomerates via particle coarsening.

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Particulate matter (PM) samples were collected at a road side (Noge area) and ambient samples also taken (Kudan area) in Tokyo in summer and winter seasons from 2002 to 2012. Fine PM (PM2.5) concentrations decreased in both Noge and Kudan from 2002 while coarse PM concentrations were at a stable level. With detailed PM composition data such as carbons, elements and ions, a chemical mass balance (CMB) method was used to estimate the contribution of PM sources. In 2002, PM from auto exhaust was the dominant component of PM2.5, its ratio was 63% at Noge and 35% at Kudan, however in 2012, the ratio reduced to 6% and 2% respectively. Emission countermeasures taken in this decade were tighter control on exhaust emissions from diesel-powered vehicles, reduction in the sulfur content of diesel fuel lead PM2.5 concentration reduction. In the latter 5 years, PM2.5 concentration is stable, a lower level of PM2.5 needs a reduction of secondary particles.

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The influence of ammonia on polymer electrolyte fuel cell (PEFC) performance was investigated to determine the effect of the anode / cathode catalyst loading and anode dew point. In single cell tests, significant voltage drops were observed due to ammonia in hydrogen fuel. Changing anode or cathode catalyst loading made no difference in PEFC performance. This indicates that there is little influence of poisoning by ammonia or compounds derived from ammonia on the platinum catalyst. The cell voltage drop and membrane resistance were greater when the anode dew point was low. Ammonia may accumulate in the electrolyte membrane under low humidity conditions.

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[in Japanese]

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[in Japanese]

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