Facile sonochemical synthesis of amorphous NiFe-(oxy)hydroxide nanoparticles as superior electrocatalysts for oxygen evolution reaction

In this work, we present facile synthesis of amorphous Ni/Fe mixed (oxy)hydroxide (NiFe(H)) nanoparticles (NPs) and their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media. a-NiFe(H) NPs have received lots of attention as OER electrocatalysts with many desirable properties. By using a simple sonochemical route, we prepared amorphous Ni and Fe-alkoxide (NiFe(A)) NPs whose composition can be controlled in the entire composition range (Ni_100−xFe_x, 0 ≤ x ≤ 1). These samples are composed of extremely small NiFe(A) NPs with Ni and Fe atoms homogeneously distributed. NiFe(A) NPs are readily converted into corresponding electrocatalytically active NiFe(H) NP by a simple electrochemical treatment. Electrochemical analysis data show that the OER activity of amorphous NiFe(H) samples follows the volcano-type trend when plotted against the Fe content. Ni₇₀Fe₃₀(H) sample showed the lowest overpotential of 292 mV at 10 mA cm⁻²_geo and the lowest Tafel slope of 30.4 mV dec⁻¹, outperforming IrO_x/C (326 mV, 41.7 mV dec⁻¹). Our samples are highly durable based on the chronopotentiometry data at the current density of 10 mA cm⁻²_geo for 2 h which show that Ni₇₀Fe₃₀ sample maintains the steady-state potential, contrary to the time-varying IrO_x/C.