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.La₂NiO₄是一种极具应用前景的中低温固体氧化物电池阴极材料，因其兼具优异的电子与离子导电性，且氧交换活性高、活化能低。La₂NiO₄（LNO）薄膜中的氧掺入与输运过程受限于表面反应，因此通过调控其形貌有望全面提升电极性能。本文报道了采用等离子体增强金属有机化学气相沉积（PI-MOCVD）法生长纳米结构化La₂NiO₄薄膜电极的研究，成功制备出具有垂直间隙柱状结构的薄膜，其活性表面积较传统薄膜成倍提升，可加速氧交换过程。该纳米棒结构根植于致密底层，该底层可作为优异的电子与离子传导通路。通过调控生长温度可精准调控其微观结构，并采用扫描电子显微镜（SEM）、透射电子显微镜（TEM）与X射线衍射（XRD）对其进行表征。我们针对不同厚度、生长于单晶衬底上的致密型与柱状结构La₂NiO₄薄膜，通过电导率弛豫测量研究了其表面活性的影响。研究结果表明，表面积的提升结合不同表面终止态的暴露，可显著提升柱状结构薄膜的总交换活性。