Stability limitations for Pt/Sn-In2O3 and Pt/In-SnO2 in acidic electrochemical systems

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.