サイクリックボルタンメトリー法による固体高分子形燃料電池の発電状態カソード有効電極触媒面積の解析

摘要

固体高分子形燃料電池（PEFC）は水素と空気中のrn酸素から電気エネルギーを高効率で生成でき，水しかrn排出しないことから，次世代のエネルギーデバイスとrnして研究が盛んに行われている．PEFCの安定運転やrn性能維持のためには，運転中のPEFCの状態検知が重rn要であり，著者らは電気化学インピーダンス分光法にrnょる診断法を追求してきた.%To maintain stable and high performance of a PEFC. sufficient three-phase boundary at the electrode catalyst of the cathode is necessary so that the catalyst works effectively. Measurement of the active electrode catalyst area of the cathode of an operating PEFC allows to detect the performance degradation. We have therefore investigated the area by cyclic voltammetry. Relation between peak current for the oxygen reduction reaction and square root of scan rate of an unconventionally fast scan and large current cyclic voltammogram is found to give the active area under power generation. We thereby observe decreases in the area due to catalyst degradation associated with operating duration of a cell and due to a decrease in humidity of fed air. This information under power generation cannot be obtained from the conventional method that measures the charge of underpotential deposition (UPD) of hydrogen at the catalyst. Taking into account diffusion of dissolved oxygen in liquid water layer adjacent to the catalyst layer, more reasonable area is estimated than that calculated with the conventional gas-phase oxygen diffusion model. The area estimated is one order of magnitude larger than that from the conventional UPD method.