Operando X-ray absorption spectroscopy of hyperfine β-FeOOH nanorods modified with amorphous Ni(OH) under electrocatalytic water oxidation conditions.

Operando X-ray absorption spectroscopy was employed to study an active electrocatalyst, hyperfine β-FeOOH nanorods (∅ 3 × 15 nm) surface-modified with amorphous Ni hydroxide. The nearest neighbor structure and valence of Fe ions did not change under water oxidation conditions, while changes in the nearest neighbor ordering of Ni ions and a reversible transition to Ni were observed in accordance with the electrical bias for the reaction.