Layered Fe-Substituted LiNiO₂ Electrocatalysts\nfor High-Efficiency Oxygen Evolution Reaction

Abstract

LiNi_1–<i>x</i>Fe_<i>x</i>O₂ (0 ≤ <i>x</i> ≤ 0.3)\nand Li_<i>y</i>Ni_0.8Fe_0.2O₂ (0.8 ≤ <i>y</i> ≤ 1.2) catalysts\nfor the oxygen evolution reaction (OER) were systematically investigated\nto discover the influence of the composition and layered structure\non electrochemical activity. LiNi_0.8Fe_0.2O₂ exhibits OER activity that is better than that of LiNiO₂ and other Fe-substituted LiNiO₂ catalysts, while\nLi_1.2Ni_0.8Fe_0.2O₂ shows\nOER activity that is much higher than that of LiNi_0.8Fe_0.2O₂ and Li_0.8Ni_0.8Fe_0.2O₂. The best OER activity is achieved on Li_1.2Ni_0.8Fe_0.2O₂ with a Tafel\nslope of 59 mV dec^–1 and a current density\nof 10 mA cm^–2 at an overpotential of 302\nmV, better than that for the benchmark IrO₂ catalyst. Combined\nwith the density functional theory calculations, the enhanced OER\nactivity is mainly attributed to the unique electronic structure derived\nfrom the interaction of Li, Ni, and Fe in the materials and the layered\nstructure which plays an important role in stabilizing the high valence\nstates of Ni and Fe during the OER.