Based on the chemical stability of group IV and V elements in acidic solutions, TaOx nanoparticles prepared by electrodeposition in an ethanol-based Ta plating bath at room temperature were investigated as novel nonplatinum electrocatalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs). Electrodeposition conditions of Ta complexes and subsequent various heat treatments for the deposited TaOx were examined for the best performance of the ORR. TaOx particles on carbon black (CB), electrodeposited at a constant potential of -0.5 V Ag/AgCl for 10 s and then heat-treated by pure H2 flow at 523 K for 1 h, showed excellent catalytic activity with an onset potential of 0.93 VRHE (for 2 μA cm-2) for the ORR. Surface characterizations of the catalysts were performed by scanning transmission electron microscopy (STEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). The loading amounts of the electrodeposited material on the CB were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). All the physical results suggested that high dispersion of TaOx particles on the CB surface with 2-3 nm size was critical and key for high activity. The chemical identity and modified surface structure for the deposited TaOx catalysts before and after H 2 heat treatment were analyzed by X-ray photoelectron spectroscopy (XPS). The formation of more exposed active sites on the electrode surface and enhanced electroconductivity of the tantalum oxide promoted from the H 2 treatment greatly improved the ORR performance of the electrodeposited TaOx nanoparticles on CB. Finally, the highly retained ORR activity after an accelerated durability test in an acidic solution confirmed and proved the chemical stability of the oxide nanoparticles. The high utilization of the electrodeposited TaOx nanoparticles uniformly dispersed on CB for the ORR was comparable to that of commercial Pt/CB catalysts, visually demonstrating their catalytic potential for PEFC electrocatalysts. © 2013 American Chemical Society.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This work was supported in part by the Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST) of the Cabinet Office of Japan and "Elements Strategy Initiative for Catalysts & Batteries (ESICB)" supported by the MEXT program "Elements Strategy Initiative to Form Core Rersearch Center" (since 2012) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. This work also contributes the international exchange program of the A3 Foresight Program of the Japan Society for the Promotion of Science (JSPS). One of authors, Seo, appreciates the support of the Global Centers of Excellence (GCOE) Program of JSPS for her work at the University of Tokyo.
ASJC Scopus subject areas
- Surfaces, Coatings and Films
- Physical and Theoretical Chemistry
- Electronic, Optical and Magnetic Materials