Layered Fe-Substituted LiNiO₂ Electrocatalysts for High-Efficiency Oxygen Evolution Reaction

LiNi 1– x Fe x O 2 (0 ≤ x ≤ 0.3) and Li y Ni 0.8 Fe 0.2 O 2 (0.8 ≤ y ≤ 1.2) catalysts for the oxygen evolution reaction (OER) were systematically investigated to discover the influence of the composition and layered structure on electrochemical activity. LiNi 0.8 Fe 0.2 O 2 exhibits OER activity that is better than that of LiNiO 2 and other Fe-substituted LiNiO 2 catalysts, while Li 1.2 Ni 0.8 Fe 0.2 O 2 shows OER activity that is much higher than that of LiNi 0.8 Fe 0.2 O 2 and Li 0.8 Ni 0.8 Fe 0.2 O 2 . The best OER activity is achieved on Li 1.2 Ni 0.8 Fe 0.2 O 2 with a Tafel slope of 59 mV dec –1 and a current density of 10 mA cm –2 at an overpotential of 302 mV, better than that for the benchmark IrO 2 catalyst. Combined with the density functional theory calculations, the enhanced OER activity is mainly attributed to the unique electronic structure derived from the interaction of Li, Ni, and Fe in the materials and the layered structure which plays an important role in stabilizing the high valence states of Ni and Fe during the OER.