Oxygen reduction on nanocrystalline ruthenia – local structure effects

  • 10.1039/c4ra10001h
  • RSC Advances
  • p 1-2, 5, 2,
  • journal-article
Nanocrystalline ruthenium dioxide and doped ruthenia of the composition Ru 1− x M x O 2 (M = Co, Ni, Zn) with 0 ≤x ≤ 0.2 were prepared by the spray-freezing freeze-drying technique. The oxygen reduction activity and selectivity of the prepared materials were evaluated in alkaline media using the RRDE methodology. All ruthenium based oxides show a strong preference for a 2-electron oxygen reduction pathway at low overpotentials. The catalysts' selectivity shifts towards the 4-electron reduction pathway at high overpotentials ( i.e. at potentials below 0.4 Vvs. RHE). This trend is particularly noticeable on non-doped and Zn-doped catalysts; the materials containing Ni and Co produce a significant fraction of hydrogen peroxide even at high overpotentials. The suppression of the 4-electron reduction pathway on Ni and Co-doped catalysts can be accounted for by the presence of the Ni and Co cations in thecus binding sites as shown by the DFT-based analyses on non-doped and doped catalysts.