Catalytic Activity for Oxygen Reduction Reaction on Tantalum Oxide-Based Compounds (1) Effect of Preparation Conditions of Thin Film Model Catalysts Using Reactive Sputtering Method on Oxygen Reduction Activity

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 02 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.