Oxygen Electrocatalysis on Some Oxide Pyrochlores

Abstract

Pyrochlore structure oxides described by the formula A2[B2_xAx]7_y, where A = Pb or Bi, B = Ru or Ir, 0 <~x <1 and 0 ~<y ~<0.5, have been evaluated for oxygen electrocatalysis. In alkaline electrolyte between room temperature and ll0~ these materials display significantly lower polarizations than any other catalyst for O2 evolution and are among the best for O2 reduction. Rotating ring disk experiments have not detected soluble H20~ as an intermediate during 02 reduction. It has been established that reasonable activity maintenance is achievable over relatively long periods (500-1800 hr).) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2014-12-08 to IP

Prospects for alkaline zero gap water electrolysers for hydrogen production

“…Pyrochloretype oxides have the general formula A 2 [B 2Àx A x ]O 7Ày , where A ¼ Pb or Bi, B ¼ Ru or Ir, 0 < x < 1 and 0 < y < 0.5. Horowitz and coworkers [83] [84]. The pyrochlores give a low Tafel slope, 24e40 mV dec À1 and their high activity of these oxides was explained in terms of their oxygen deficiency.…”

Oxygen Vacancies in Pyrochlore Oxides: Powder Neutron Diffraction Study of Pb2Ir2O6.5and Bi2Ir2O7−y

“…For the Bi atom movement along the threefold axis, that is toward that more than one such species is involved. Such a result is in contrast to the diffraction results which suggest that the two closest O atoms, is inhibited; the principal vibration is parallel to the [111] direction, is given by U 11 ϩ 2U 12 ϭ bulk formation of Ir(V) is not possible in the pyrochlores; although obviously this does not preclude formation of 5.7 ϫ 10 3Ϫ Å 2 , and is noticeably smaller than movements perpendicular to this direction, U 11 Ϫ U 12 ϭ 13.8 ϫ 10 The refined values for the Pb and Ir atom positions at 16e (x, x, x) x Pb ϭ 0.8775(1) and x Ir ϭ 0.3755 (1) show that the Pb has been displaced significantly from the Fd3m inversion symmetry position x Pb ϭ 0.875, moving 0.044(1) spectra with a single doublet, the measure of fit being an unacceptably high 7.0%. Considering the spectra to consist Å toward its assocaited vacancy so that along the [111] direction the Pb-vacancy distance is 2.178 Å while the of two doublets led to a reduction in R to 2.2%.…”

A Sol–Gel Route for the Synthesis of Bi2Ru2O7 Pyrochlore Oxide for Oxygen Reaction in Alkaline Medium

“…, where A"Pb or Bi, 04x41 and 04y40.5, have demonstrated high catalytic activity for oxygen reduction as well as for oxygen evolution, and have emerged as possible candidates for use in secondary metal}air batteries (2). These compounds have also promoted the selective electrooxidation of certain organics (3).…”