Kinetic Study on Superior Performance of Silica-Coated Cathode Catalysts for PEFC

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We have reported that supported Pt catalysts covered with silica layer showed extremely high durability for the cathode in PEFC, but the layer might limit reaction rate due to slow mass transfer within the silica layer. In this work we studied on the mass transfer in silica layer and on the reason for the superior durability of the coated catalyst. The structure of silica layer was successfully controlled by changing coating condition. The silica layer prepared using methyltriethoxysilane has larger pore size and exhibited both the high activity and high durability. The reason why the coating catalysts show high durability could not be revealed, but the interaction between metal surface and silica layer, or positive charge of silica layer might suppress the dissolution of Pt species during reaction. Finally, it was also found that the coated Pd-Co catalysts showed extremely high durability for the cathode in PEFC, as compared with uncoated catalysts.