Amorphous Ni<sub>1–<i>x</i></sub>Fe<sub><i>x</i></sub> Oxyhydroxide Nanosheets with Integrated Bulk and Surface Iron for a High and Stable Oxygen Evolution Reaction
Birhanu Bayissa Gicha, Lemma Teshome Tufa, Youngeun Choi, Jaebeom Lee
Abstract
Ni-based electrocatalysts, especially with Fe, are attractive electrocatalysts for oxygen evolution reaction (OER) due to their exhilarating surface properties and anticipated synergistic effect. Herein, amorphous Ni1–xFex oxyhydroxide nanosheets (x: 0, 0.25, 0.50, 0.75, and 1) with integrated bulk and surface Fe were synthesized by facile electrodeposition as an active and stable electrocatalyst for OER. Different ratios of Fe and Ni precursors were deposited on nickel foam cathodically for bulk Fe (FeB) embodiment. Then, surface Fe (FeS) was integrated through anodic cycling from Fe-containing KOH. Benefiting from the amorphous structure and integration between FeB and FeS, high activity and stability were achieved. Accordingly, FeB+S-NIFE25 has demonstrated the highest OER activity, with the lowest overpotential of 300 mV at a current density of 50 mA cm–2, a Tafel slope as low as 30 mV dec–1, and robust stability exceeding 100 h for continuous oxygen generation while the same material (NIFE25) in the absence of FeS, has demonstrated relatively a higher overpotential of 340 mV and a Tafel slope of 65 mV dec–1. Computation simulation also calculated that the NIFEX composites containing both FeB and FeS demonstrated weak binding energies enhancing OH– density at the reaction interface facilitating O2 generation. It is probable that the synergy between FeB and FeS coupled with an amorphous structure induces higher OER activity and stability and can be readily applied to generate cheap and clean hydrogen energy.