Synergistic effects in oxygen evolution activity of mixed iridium-ruthenium pyrochlores

Pyrochlore oxides (A2B2O7 ) simultaneously containing iridium and ruthenium in the B-site are promising catalysts for oxygen evolution reaction (OER) in acid media. The catalytic activity of the pyrochlore basedcatalysts is increased by the coexistence of Ir and Ru in the B-site of the pyrochlore structure. Lanthanide(Yb, Gd, or Nd) stabilized mixed pyrochlores with a fraction of Ru in the B-site of x Ru = 0.2, 0.4, 0.6, 0.8were synthesized by the spray-freeze freeze-dry approach. All prepared mixed pyrochlore catalysts aresurpassing the OER activity of the corresponding iridium and ruthenium analogues featuring no cationmixing as well as that of the benchmark IrO2 catalyst. The synergy of Ir and Ru in the B-site of thepyrochlore structure suppresses the effect of the A-site cation radius on the OER activity. The observedOER activity scales with the Ir-Ru bond distance which represents the local structure of the preparedmaterials. The most active ytterbium catalyst also shows a significant stability improvement under OERoperando conditions over the benchmark IrO2&nbsp