Porous LaCo_1-xNi_xO_3-δ Nanostructures as an Efficient Electrocatalyst for Water Oxidation and for a Zinc-Air Battery

Perovskites have emerged as promising earth-abundant alternatives to precious metals for catalyzing the oxygen evolution reaction (OER). Herein, we report the synthesis of a series of porous perovskite nanostructures, LaCo_0.97O_3-δ, with systematic Ni substitution in Co octahedral sites. Their electrocatalytic activity during the water oxidation reaction was studied in alkaline electrolytes. The electrocatalytic OER activity and stability of the perovskite nanostructure was evaluated using the rotating disk electrode technique. We show that the progressive replacement of Co by Ni in the LaCo_0.97O_3-δ perovskite structure greatly altered the electrocatalytic activity and that the La(Co_0.71Ni_0.25)_0.96O_3-δ composition exhibited the lowest OER overpotential of 324 and 265 mV at 10 mA cm^-2 in 0.1 M KOH and 1 M KOH, respectively. This value was much lower than that of the noble metal catalysts, IrO₂, Ru/C, and Pt/C. Furthermore, the La(Co_0.71Ni_0.25)_0.96O_3-δ nanostructure showed outstanding electrode stability, with no observable decrease in performance up to 114th cycle in the auxiliary linear sweep voltammetry that lasted for 10 h in chronoamperometry studies. The excellent oxygen evolution activity of the La(Co_0.71Ni_0.25)_0.96O_3-δ perovskite nanostructure can be attributed to its intrinsic structure, interconnected particle arrangement, and unique redox characteristics. The enhanced intrinsic electrocatalytic activity of the La(Co_0.71Ni_0.25)_0.96O_3-δ catalyst was correlated with several parameters, such as the electrochemical surface area, the roughness factor, and the turnover frequency, with respect to variation in the transition metals of the perovskite structure. Subsequently, La(Co_0.71Ni_0.25)_0.96O_3-δ was utilized as the air cathode in a zinc-air battery application.