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Electrocatalytic Oxygen Evolution over Supported Small Amorphous Ni–Fe Nanoparticles in Alkaline Electrolyte

Qiu, Yang, Xin, Le, Li, Wenzhen
Langmuir 2014 v.30 no.26 pp. 7893-7901
anodes, carbon, carbon dioxide, catalysts, cathodes, corrosion, durability, electrochemistry, electrolytes, energy conversion, fuels, hydrogen, hydrogen production, iron, nanoparticles, nickel, oxidation, oxygen production, potassium hydroxide, renewable energy sources, transmission electron microscopy
The electrocatalytic oxygen evolution reaction (OER) is a critical anode reaction often coupled with electron or photoelectron CO₂ reduction and H₂ evolution reactions at the cathode for renewable energy conversion and storage. However, the sluggish OER kinetics and the utilization of precious metal catalysts are key obstacles in the broad deployment of these energy technologies. Herein, inexpensive supported 4 nm Ni–Fe nanoparticles (NiyFe₁–yOₓ/C) featuring amorphous structures have been prepared via a solution-phase nanocapsule method for active and durable OER electrocatalysts in alkaline electrolyte. The Ni–Fe nanoparticle catalyst containing 31% Fe (Ni₀.₆₉Fe₀.₃₁Oₓ/C) shows the highest activity, exhibiting a 280 mV overpotential at 10 mA cm–² (equivalent to 10% efficiency of solar-to-fuel conversion) and a Tafel slope of 30 mV dec–¹ in 1.0 M KOH solution. The achieved OER activity outperforms NiOₓ/C and commercial Ir/C catalysts and is close to the highest performance of crystalline Ni–Fe thin films reported in the literature. In addition, a Faradaic efficiency of 97% measured on Ni₀.₆₉Fe₀.₃₁Oₓ/C suggests that carbon support corrosion and further oxidation of nanoparticle catalysts are negligible during the electrocatalytic OER tests. Ni₀.₆₉Fe₀.₃₁Oₓ/C further demonstrates high stability as there is no apparent OER activity loss (based on a chronoamperometry test) or particle aggregation (based on TEM image observation) after a 6 h anodization test. The high efficiency and durability make these supported amorphous Ni–Fe nanoparticles potentially applicable in the (photo)electrochemical cells for water splitting to make H₂ fuel or CO₂ reduction to produce usable fuels and chemicals.