Tailored nano-columnar La2NiO4 cathodes for improved electrode performance

La2NiO4 is a promising cathode material for intermediate and low temperature solid oxide cell applications, due to good electronic and ionic conductivity and high oxygen exchange activity with a low activation energy. Oxygen incorporation and transport in La2NiO4 (LNO) thin films is limited by surface reactions. Hence, tailoring the morphology is expected to lead to an overall improvement of electrode performance. We report on the growth of to nano-architectured La2NiO4 thin film electrodes by PI-MOCVD, achieving vertically gapped columns with multi-fold active surface area, leading to faster oxygen exchange. This nano-rod 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 columnar-structured La2NiO4 thin films of various thicknesses on single crystal substrates. Our results indicate 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 columnar structured films.