Multicomponent proton conducting ceramics of SiO₂ - TiO ₂ - ZrO₂ - P₂O₅ - Bi ₂O₃ for an intermediate temperature fuel cell

The multicomponent proton conducting ceramics SiO₂-TiO ₂- ZrO₂-P₂ O₅ (STZP) and SiO ₂-TiO₂- ZrO₂-P₂ O ₅-Bi₂ O₃ with three different compositions (STZPBi3, STZPBi10, and STZPBi15) were synthesized via a wet chemical route. These prepared materials showed good thermal stability up to around 900°C by TG/DTA analyses. Introduction of optimum quantity of bismuth as a sintering aid into the samples contributed to enhance the densification of microstructure, which is essential for the utilization of proton conducting ceramics in fuel cells operated at elevated temperature. The proton conductivity of STZP was 3.6 × 10^-5 S/cm at 80°C and that of STZPBi10 was 4.6 × 10^-3 S/cm at 180°C. The fuel cell performances using STZP and STZPBi10 were implemented at 80°C and up to 230°C, respectively. The maximum power density was 0.03 mW/ cm² at 80°C for the STZP sample and 2.5 mW/ cm² at 150°C for the STZPBi10 sample under wet hydrogen and dry oxygen. The reduction of CO poisoning on platinum catalyst was demonstrated in fuel cell operating at temperatures of 180°C, 200°C, and 230°C.