Utilising intrinsic self-protecting properties of Ni-alloys in fuel electrodes of solid oxide electrolysis cells

The degradation of the fuel electrode composite of Ni and an oxide ion conducting oxide is a central challenge to solve for competitive long-term performance of a solid oxide electrolysis cell (SOEC) to produce green hydrogen. In this study, enhanced durability is observed using microstructural changes in Ni-alloy/Y 2 O 3 stabilised ZrO 2 (YSZ) fuel electrodes as an intrinsic self-protecting mechanism. In particular, Ni–Fe alloys offer benefits through the intrinsic mobility of Fe in the alloy phase amid the application of cathodic potentials. This mobility of Fe forms protective surface layers around the Ni–Fe particles and enhances durability by: (1) preventing the loss of contact and mobility of the metal phase away from the most active reaction zones during Ni migration and (2) protecting the surface against accumulation of trace impurities of Si as a ubiquitous contaminant in H 2 O atmospheres. The combined approach of electrochemical testing of alloy thin-film fuel electrodes prepared by photolithography, postmortem characterisation by low-energy ion scattering (LEIS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) with density functional theory (DFT) calculations is used to establish a mechanism for self-protecting electrode properties. In addition, other Ni-alloys (Ni–V, Ni–Mn) are proposed by DFT as promising electrode materials with self-protecting properties. • Ni-alloy electrodes are analysed for their durability in solid oxide electrolysis cells. • Cleanroom prepared NiFe and NiCu (80–20 and 95–5 wt%) electrodes are studied. • It is found that Ni with 20 wt% Fe offers intrinsic self-protecting properties. • Low energy ion scattering reveals the protective effect of Fe against Si impurities. • NiMn and NiV are shown as other self-protecting alloys by density functional theory.