Highly durable Pt cathode catalysts for polymer electrolyte fuel cells; coverage of carbon black-supported Pt catalysts with silica layers

Carbon black-supported Pt (Pt/CB) catalysts that have been used at the cathode in state of the art polymer electrolyte fuel cell (PEFC) were covered with silica layers to improve the durability of the Pt catalysts under PEFC cathode conditions. The durability of silica-coated Pt/CB to potential cycling between 0.6 and 0.9 V (vs. reversible hydrogen electrode (RHE)) was strongly dependent on the thickness of the silica layers, i.e., the durability of Pt/CB improved after coverage with thick silica layers. However, the coverage of the whole surface of the Pt/CB catalysts with silica layers produced electrochemically inactive Pt catalysts. Silica-coated Pt/CB catalysts with an optimal silica layer thickness showed similar activity for the oxygen reduction reaction compared to Pt/CB catalysts without a silica coating, and they had excellent durability at the cathode in a PEFC single cell. Coverage with silica layers improved the durability of the Pt/CB cathode catalysts without a decrease in the catalytic activity for the oxygen reduction reaction.

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► Coverage of carbon black-supported Pt metal with silica layers (SiO2/Pt/CB).
► SiO2/Pt/CB cathode catalyst for oxygen reduction in fuel cells.
► Coverage of Pt/CB with silica inhibits Pt metal growth under cathode conditions.
► Coverage with silica does not decrease the catalytic activity of Pt/CB.