Abstract
Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. Here, we report a promisingly dendritic core-shell nickel-iron-copper metal/metal oxide electrode, prepared via dealloying with an electrodeposited nickel-iron-copper alloy as a precursor, as the catalyst for water oxidation. The as-prepared core-shell nickel-iron-copper electrode is characterized with porous oxide shells and metallic cores. This tri-metal-based core-shell nickel-iron-copper electrode exhibits a remarkable activity toward water oxidation in alkaline medium with an overpotential of only 180 mV at a current density of 10 mA cm−2. The core-shell NiFeCu electrode exhibits pH-dependent oxygen evolution reaction activity on the reversible hydrogen electrode scale, suggesting that non-concerted proton-electron transfers participate in catalyzing the oxygen evolution reaction. To the best of our knowledge, the as-fabricated core-shell nickel-iron-copper is one of the most promising oxygen evolution catalysts.
Highlights
Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction
We design the alloy by choosing Ni, Fe, and Cu as the codepositing elements for the following reasons: (i) single metal center Ni, Fe, and Cu-based oxides have been reported as efficient catalysts for oxygen evolution reaction (OER);[9, 10, 22] (ii) The co-depositing species stick on the same type but hardly stick to particles of the other type20. (iii) Cu species is selected to be corroded to enhance the interfacial surface area[23,24,25]
The X-ray powder diffraction (XRD) spectrum of NiFeCu alloy reveals that the as-prepared film formed a solid solution with a face-centered cubic structure (Supplementary Fig. 2)[20]
Summary
Electrochemical water splitting requires efficient water oxidation catalysts to accelerate the sluggish kinetics of water oxidation reaction. NiFe-15, NiV-16, Ni60Fe30Mn10-10, NiFeCr-based[14] metal oxides, and gelled FeCoW oxyhydroxide[17] showed better performance than single metal center Ni oxides These reports inspired us to synthesize tri-transition metal-based alloy as templated precursors to highly active core-shell (CS) metal/metal oxide OER catalysts. The parent alloy with dendritic structure is prepared via electrodeposition This alloy is used as a precursor to fabricate a CS metal/metal oxide electrode with a high electrochemically active surface area (ECSA). This CS–NiFeCu is employed as an electrode for OER, showing an overpotential of only 180 mV for a current density of 10 mA cm−2. This is, to the best of our knowledge, the most-efficient OER catalyst in basic media in terms of the overpotential required at 10 mA cm−2
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