In Situ Detection of Iron in Oxidation States ? IV in Cobalt?Iron Oxyhydroxide Reconstructed during Oxygen Evolution Reaction

Cobalt-iron oxyhydroxides (CoFeOOHx) are among the most active catalysts for oxygen evolution reaction (OER). However, their redox behavior and electronic chemical structure of sites still ambiguous. To shed more light on this, complete rapid reconstruction four helical cobalt-iron borophosphates with different Co:Fe ratios into disordered can be achieved, which electrolyte-penetrable thus transition metal potentially participate in OER. track to identify structure, quasi situ X-ray absorption spectroscopy is applied. Iron high oxidation states ? IV (Fe4+) its substantial an average state around 2.8 above 3.2 detected. Furthermore, a 6% contraction Fe-O bond length compared Fe3+OOH references observed during OER strong distortion [MO6] octahedra identified. It hypothesized that this caused by presence oxyl radicals di-µ-oxyl radical bridged centers sites. anticipated detailed structural description substantially contribute debate nature site bimetallic iron-containing catalysts.