Cyanogel-Based Preparation of Amorphous NiFe Nanoaggregates with Enhanced Activity and Stability for OER

The development of cost-efficient electrocatalysts for oxygen evolution reaction (OER) with high efficiency is crucial to widespread applications of water splitting for hydrogen production. In this work, porous three-dimensional (3D) amorphous NiFe nanoaggregates composed of interconnected nanograins were synthesized by a cyanogel-based wet chemical reduction method using the NiCl2/Na4Fe(CN)6 cyanogel as the precursor and NaBH4 as the reducing agent. The influence of the incorporated Fe amount was carefully studied by slightly changing the feeding molar ratios of the Ni/Fe atoms in the precursors. The intrinsic 3D backbone structure of the cyanogel resulted in crystal nuclei tending to generate along with the backbones, which is key to the formation of NiFe nanoaggregates with a porous 3D interconnected structure. The synthesized NiFe nanoaggregates with a 3D interconnected structure and high porosity, as well as the incorporation of Fe, are in favor of high surface area, more active sites, and abundant oxygen vacancies, leading to superior activity and stability of OER in alkaline electrolytes with a low overpotential of 0.35 V at 10 mA cm−2, a high current density of 24.8 mA cm−2 at 1.65 V, a small Tafel slope of 76.9 mV dec−1, and attractive durability in 1 M KOH solution.