Analysis of Performance Losses and Degradation Mechanism in Porous La2−X NiTiO6−δ:YSZ Electrodes

Abstract

The electrode performance and degradation of 1:1 La2−xNiTiO6−δ:YSZ composites (x = 0, 0.2) has been investigated to evaluate their potential use as SOFC cathode materials by combining electrochemical impedance spectroscopy in symmetrical cell configuration under ambient air at 1173 K, XRD, electron microscopy and image processing studies. The polarisation resistance values increase notably, i.e., 0.035 and 0.058 Ωcm2 h−1 for x = 0 and 0.2 samples, respectively, after 300 h under these demanding conditions. Comparing the XRD patterns of the initial samples and after long-term exposure to high temperature, the perovskite structure is retained, although La2Zr2O7 and NiO appear as secondary phases accompanied by peak broadening, suggesting amorphization or reduction of the crystalline domains. SEM and TEM studies confirm the ex-solution of NiO with time in both phases and also prove these phases are prone to disorder. From these results, degradation in La2−xNiTiO6−δ:YSZ electrodes is due to the formation of La2Zr2O7 at the electrode–electrolyte interface and the ex-solution of NiO, which in turn results in the progressive structural amorphization of La18NiTiO6−δ phases. Both secondary phases constitute a non-conductive physical barrier that would hinder the ionic diffusion at the La2−xNiTiO6−δ:YSZ interface and oxygen access to surface active area.

A Review of X-ray Photoelectron Spectroscopy Technique to Analyze the Stability and Degradation Mechanism of Solid Oxide Fuel Cell Cathode Materials

“…The CPE in the equivalent circuit can be expressed as follows [ 51 ]: where ω = 2· π · f· ( f is the frequency), Q is the pseudocapacitance, j is equal to and n is the empirical constant value between 0 and 1. The actual capacitance value can be calculated using Equation (3), as follows [ 24 ]: …”

“…Mechanical analyses of the SOFC cathode are generally limited and not critical because of the porous structure of the cathode materials utilized, which are not used as freestanding support. Many new advanced techniques have been adopted, and researchers have extensively studied the microstructural distortion and gradual degradation of the electrochemical performance of energy materials [ 24 ].…”

Synthesis and Characterization of LaNi0.5Ti0.5O3 and La2NiTiO6 Double Perovskite Nanoparticles

“…Pérez-Flores et al [ 13 , 16 ] synthesized La 2−x Sr x NiTiO 6- δ (0 ≤ x ≤ 0.5) materials using a final temperature treatment of 1773 K, for 24 h, with an average crystallite size of approximately 8 nm. Moreover, this same group reported the synthesis of the La 2−x NiTiO 6 (0 ≤ x < 0.2) perovskites [ 17 ], along with La 2 NiTiO 6 [ 18 ]. For the last double perovskite, the particle size ranged from 40 to 80 nm.…”