Abstract
The high activity of non-platinum electrocatalysts for oxygen reduction reaction (ORR) in alkaline media is necessary for applications in energy conversion devices such as fuel cells and metal-air batteries. Herein, we present the electrocatalytic activity of TaOx/carbon black (CB) nanoparticles for the ORR in an alkaline atmosphere as well as in an acidic electrolyte. Ultrafine TaOx nanoparticles 1–2 nm in size and uniformly dispersed on CB supports were prepared by potentiostatic electrodeposition in a nonaqueous electrolyte and subsequent annealing treatment in an H2 flow. The TaOx/CB nanoparticles largely catalyzed the ORR with an onset potential of 1.03 VRHE in an O2-saturated 0.1 M KOH solution comparable to that of a commercial Pt/CB catalyst. ORR activity was also observed in 0.1 M H2SO4 solution. According to the rotating ring disk electrode measurement results, the oxide nanoparticles partly produced H2O2 during the ORR in 0.1 M KOH, and the ORR process was dominated by both the two- and four-electron reductions of oxygen in a diffusion-limited potential region. The Tafel slope of −120 mV dec−1 in low and high current densities revealed the surface stability of the oxide nanoparticles during the ORR. Therefore, these results demonstrated that the TaOx/CB nanoparticles were electroactive for the ORR in both acidic and alkaline electrolytes.
Highlights
Oxygen reduction reaction (ORR) is a critical step in renewable energy conversion systems such as fuel cells and metal-air batteries because the reaction is driven by sluggish and complex four-electron transfer over electrocatalyst surfaces determining the reaction kinetics and activity [1,2]
Ultrafine tantalum oxide particles (TaOx) nanoparticles were deposited on carbon black (CB) supports by potentiostatic electrodeposition in a nonaqueous Ta-based solution, followed by annealing treatment in an
We demonstrated the catalytic activity of TaOx /CB nanoparticles in the ORR in both acidic and alkaline media
Summary
Oxygen reduction reaction (ORR) is a critical step in renewable energy conversion systems such as fuel cells and metal-air batteries because the reaction is driven by sluggish and complex four-electron transfer over electrocatalyst surfaces determining the reaction kinetics and activity [1,2]. The ORR activity over TaOx nanoparticles supported on CB (TaOx /CB) was retained to approximately 94% of the initial current density during an accelerated long-term operation test for 10,000 cycles, demonstrating its high catalytic stability in an acidic electrolyte. The current density for an ORR was strongly dependent upon the size of the TaOx nanoparticles, and oxide particles of 1~2 nm in size drove the ORR process via a four-electron transfer pathway, comparable to that of the commercial Pt/CB catalyst [23]. These results indicated that TaOx /CB nanoparticles were a promising electrocatalyst for an ORR in acidic media. A kinetic study of the oxide nanoparticles was performed using a rotating (ring) disk electrode (R(R)DE)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
