Mixed metal catalysts containing Pt, Ir, Ru, Os, and Rh were synthesized on three different conductive oxide supports, Ebonex, which is a mixture of Ti4O7 and other phases, phase-pure microcrystalline Ti4O7, and Ti0.9Nb0.1O2, a doped rutile compound. Ebonex-supported catalysts were prepared as arrays and screened combinatorially for activity and stability as bifunctional oxygen reduction/water oxidation catalysts. The highest activity and stability was found in the Pt-Ru-Ir ternary region at compositions near Pt4Ru4Ir1. X-ray near edge absorption spectra indicated a significant electronic interaction between the catalyst and the support, and a substantial increase in catalyst utilization was observed, even though the support surface areas were relatively low. Both Ebonex and Ti4O7 have short-lived electrochemical stability under conditions of oxygen evolution at + 1.6 V vs. RHE in 0.5 M H2SO4. Current at these supported catalysts gradually decreases, and the decrease is attributed to loss of electronic conductivity. Ebonex and Ti4O7 are also thermally oxidized in air at temperatures above 400°C. In contrast, Ti0.9Nb0.1O2, which has a nondefective oxygen lattice, is quite resistant to electrochemical and thermal oxidation. Conditioning of Ti0.9Nb0.1O2-supported Pt4Ru4Ir1 at positive potentials had little effect on the activity of the catalyst.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry