Electromodified NiFe Alloys as Electrocatalysts for Water Oxidation : Mechanistic Implications of Time-Resolved UV/Vis Tracking of Oxidation State Changes

• Facile electromodification of metallic NiFe alloys leads to a series of NiFe oxyhydroxide surface films with excellent electrocatalytic performance in alkaline water oxidation. During cyclic voltammetry and after sudden potential jumps between noncatalytic and catalytic potentials, Ni oxidation/reduction was tracked with millisecond time resolution by a UV/Vis reflectance signal. Optimal catalysis at intermediate Ni/Fe ratios is explained by two opposing trends for increasing Fe content: a)pronounced slowdown of the Ni2+/Ni3+ oxidation step and b)increased reactivity of the most oxidized catalyst state detectable at catalytic potentials. This state may involve an equilibrium between Ni4+ ions and Ni2+ ions with neighboring ligand holes, possibly in the form of bound peroxides.

Ämnesord

NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

Nyckelord

electrocatalysis

NiFe oxyhydroxides

spectroelectrochemistry

water oxidation

X-ray photoelectron spectroscopy

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