Evaluation of La2NiO4 as Anode Material for Solid Oxide Electrolyser Cells

Rising capacities in renewable energy production pose major challenges resulting from the decoupling between supply and demand, which requires long-range distribution and storage of electrical power. Electrolysis of water is considered a promising method for converting, storing and distributing surplus electrical energy in chemical form. Stimulated by the large-scale installation of wind parks, interest in high temperature steam electrolysis as a highly efficient means for hydrogen production is reviving. This technology appears to be especially favourable if external heat sources from power plants or industrial facilities can be utilised to assist in sustaining operating temperatures above 600°C.

High temperature electrolysis is based on solid oxide electrolyser cells (SOEC) which adopt design concepts and materials developed for solid oxide fuel cells (SOFC). In this work the promising SOFC cathode material La₂NiO_4+δ is investigated with respect to its suitability as anode for SOEC application. Important material properties characterising electrical conductivity and oxygen transport kinetics are determined on densely sintered samples of La₂NiO_4+δ. In addition, its performance as air electrode is investigated on asymmetric cells under anodic polarisation at current densities of up to -410 mAcm^-2 by means of impedance analysis and I-V measurements. Electrochemical characterisation is conducted at 800°C and 0.2 bar oxygen partial pressure and the long-term stability is studied over several thousand hours. Special emphasis is put on the effect of Cr-poisoning on the oxygen exchange kinetics and SOEC anode performance in dry and humid atmospheres. Results from post-test examination of porous electrode structures as well as dense samples of La₂NiO_4+δ by microstructural analysis with SEM-EDX and AFM are presented.