Tailored nano-columnar La$_2$NiO$_4$ cathodes for improved electrode performance

TL;DR

This paper demonstrates that nano-columnar La$_2$NiO$_4$ thin films, created via PI-MOCVD, significantly improve oxygen exchange activity for solid oxide cell cathodes by increasing surface area and optimizing microstructure.

Contribution

The study introduces a novel nano-architectured La$_2$NiO$_4$ thin film fabrication method that enhances electrode performance through tailored morphology and microstructure.

Findings

Nano-columnar La$_2$NiO$_4$ films show faster oxygen exchange.

Increased surface area improves electrode activity.

Optimized microstructure enhances overall performance.

Abstract

La$_2$NiO$_4$ is a very promising cathode material for intermediate and low temperature solid oxide cell applications, due to its good electronic and ionic conductivity, together with its high oxygen exchange activity with a low activation energy. Oxygen incorporation and transport in La$_2$NiO$_4$ (L2NO4) thin films is limited by surface reactions. Hence, tailoring the morphology is expected to lead to an overall improvement of the electrode performance. We report on the growth of nano-architectured La$_2$NiO$_4$ thin film electrodes by Pulsed Injection Metal Organic Vapour Deposition (PI-MOCVD), achieving vertically gapped columns with multi-fold active surface area, leading to much faster oxygen exchange. This nano-columnar structure is rooted in a dense bottom layer serving as good electronic and ionic conduction pathway. The microstructure is tuned by modification of the growth temperature and characterised by SEM, TEM and XRD. We studied the effect of surface activity by electrical conductivity relaxation measurements in fully dense and nano-columnar La$_2$NiO$_4$ thin films of various thicknesses grown on several different single crystal substrates. Our results demonstrate that the increased surface area, in combination with the opening of different surface terminations, leads to a significant enhancment of the total exchange activity in our films with optimized nano-architectured microstructure.