タンタル酸化物をぺ－スとした化合物の酸素還元触媒能(1)反応性スパッタ法を用いた薄膜モデル触媒の成膜条件と酸素還元活性

摘要

固体高分子形燃料電池（PEFC:Polymer electrolyte　fuelcell）は，水素などの燃料が酸化される時に発生する化学エネルギーを，直接電気エネルギーに変換するデバイスである．そのためカルノー効率の制約を受ける内燃機関に比べてエネルギー変換効率が高く，また，空気中の酸素を酸化剤として取り込むため体積・重量あたりのエネルギー容量も高い．さらに有害物質の排出も少なく，環境負荷も小さいという特徴を持つ．%Tantalum-based compounds prepared by reactive sputtering with heating were evaluated as non-platinum cathodes for poly­mer electrolyte fuel cells. Effects of species of target, TaC and TaN, and oxygen partial pressure on catalytic activity for oxygen reduction reaction (ORR) were investigated. We found that TaC target was more useful than TaN to prepare the specimen with high ORR activity. In addition, an existence of an appropriate amount of O_2 was needed with the TaC target to obtain superior catalytic activity for the ORR. X-ray diffraction and Time-of-flight secondary ion mass spectrometry analysis suggested that crystalline structure of TaON (monoclinic) and carbon on the surface might affect the catalytic activity for the ORR.