Stability Limitations for Pt/Sn–In2O3 and Pt/In–SnO2 in Acidic Electrochemical Systems

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Tin-doped indium oxide (Sn–In2O3) and indium-doped tin oxide (In–SnO2) were synthesized and investigated as the supports for platinum (Pt) electrocatalysts. The electrochemical stability of the bare and platinized oxide supports was examined from −0.8 to 1.4 V vs. NHE. The Sn–In2O3 surface was generally stable at positive potentials, but experienced severe degradation at negative potentials due to the reduction/oxidation of the surface Sn and In species. In–SnO2 supports showed significant degradation over the entire potential range, which was caused by the preferential formation of Sn, SnO and In species. Neither Sn–In2O3 nor In–SnO2 are suitable as supports for hydrogen evolution catalysts. However, it was shown that Sn–In2O3 possessed very good stability at potentials relevant to the oxygen reduction reaction (>0.6 V), which enables its application as a cathode electrocatalyst support for PEM fuel cells.