# Optimization of La2NiO4+δ Electrolysis Cell Oxygen Electrode through Surfactant-Enabled LaCoO3±δ Nanocatalyst Deposition

## TL;DR

Researchers improved the performance of a solid oxide electrolysis cell by depositing a nanocatalyst on its oxygen electrode using a surfactant method.

## Contribution

A novel surfactant-enhanced method was developed to deposit LaCoO3±δ nanocatalysts on La2NiO4+δ electrodes, enhancing oxygen exchange and reducing resistance.

## Key findings

- Surfactant-enhanced infiltration produced 88.4% pure LaCoO3±δ at low temperatures.
- Nanocoating reduced polarization resistance by ∼55% at 700 °C and 0.039 Ω·cm2 at 800 °C.
- Surface oxygen exchange coefficient improved, with a 30% reduction in activation energy.

## Abstract

Lanthanum nickelate
(LNO) has shown promise as a Cr-resistant air
electrode material for SOECs but has suboptimal surface oxygen exchange
properties. Nanocoating of the LNO surface with lanthanum cobaltite
(LCO) was chosen to improve cell performance as a surface oxygen conductor.
The work focused on the implementation of a two-step nano-LCO film
deposition utilizing catechol molecules in a porous LNO electrode.
The subgoals of the work were to maintain nanosized LCO particles/grains
to increase active surface area and to control the regularity/homogeneity
of the coating across the microstructure. To achieve these goals,
a novel surfactant-enhanced liquid infiltration method was utilized,
where nucleation sites were spread across the electrode structure
to control the location and size of LCO particles. Various catechol
surfactant compositions were evaluated for their ability to control
the kinetics of nanoparticle deposition and the homogeneity of the
coating. Chelated LCO was characterized by X-ray diffraction (XRD),
which found a substantial improvement in LCO formation with surfactant
addition and determined polymerized norepinephrine to be the best-performing
surfactant, with 88.4% pure LCO formed at low temperature. X-ray photoelectron
spectroscopy (XPS) confirmed LCO nanostructures formed by the two-step
infiltration process, showing no impurities and a stable perovskite
structure. Deposition kinetics were analyzed using atomic force microscopy
(AFM), correlating infiltration times and solution molarity to nanoparticle
size and distribution, the results of which were confirmed in symmetrical
cell samples by scanning electron microscopy (SEM). Electrochemical
impedance spectroscopy (EIS) testing demonstrated substantial improvements
in polarization resistance, where the nanocoating reduced the resistance
by ∼55% to 0.152 Ω·cm2 at 700 °C
and 0.039 Ω·cm2 at 800 °C. Electrical conductivity
relaxation (ECR) at this temperature confirmed an improved surface
oxygen exchange coefficient of the LCO + LNO heterostructure predicted
by the Bode data from EIS, alongside a reduction in activation energy
by about 30%.