Analysis of local structure of Ru_1-xNi_xO₂ electrocatalytic materials

Nanocrystalline Ru_1-xNi_xO₂ materials were synthesized by a solution method. Local structure around doped Ni atoms was characterized by extended X-ray absorption fine structure (EXAFS) functions obtained from X-ray absorption spectra acquired at Ni-K edge (8333eV). It was found that Ni ions are confined to the Ru site in the RuO₂ rutile-type crystal structure, and Ni atoms tend to group by entering neighbouring sites along the body diagonal of rutile lattice. Such a neighbourhood of two Ni atoms may act as an active site for oxygen evolution by promoting simultaneous two electron transfer from the absorbed molecule of water. The refined Ni-O bond distances suggest that oxidation state of Ni ions is between +2 and +3.