A corrosion-resistant electrocatalyst support was prepared by overcoating high surface-area diamond powder (3-6 nm diameter, 250 m2 /g) with a thin layer of boron-doped ultrananocrystalline diamond (B-UNCD) by microwave plasma-assisted chemical vapor deposition. This core-shell approach produces electrically conducting (0.4-0.5 S/cm) and high surface-area (150-170 m 2/g) diamond powder (B-UNCD-D). Accelerated degradation testing was performed by thermogravimetric analysis (TGA) to assess the oxidation resistance (i.e., corrosion resistance) of powder in the absence and presence of nanoscale Pt. The oxidation onset temperature for B-UNCD-D powder decreased with the Pt loading from 0 to 30 wt % (Pt/C). However, compared with the bare powder, the rate of carbon consumption was significantly greater for Pt-(XC-72) as compared to the platinized diamond powder. For example, the temperature of the maximum carbon consumption rate, Td, occurred at 426°C for Pt-(XC-72) (20% Pt/C), which was 295°C lower than the Td for bare XC-72. In contrast, Td for Pt-(B-UNCD-D, 20% Pt/C) was 558°C; a temperature that was only 62°C lower than that for bare diamond. Isothermal oxidation at 300°C for 5 h produced negligible weight loss for Pt-UNCD-D (20% Pt/C) while a 75% weight loss was observed for Pt-(XC-72) (20% Pt/C). The results clearly demonstrate that platinized diamond is more resistant to gas phase oxidation than is platinized Vulcan at elevated temperatures.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry