Increased performance by use of a mixed conducting buffer layer, terbia-doped ceria, for Nd2NiO4+δ SOFC/SOEC oxygen electrodes. (29th November 2019)

• Record Type: Journal Article
• Authors: Ramasamy, Devaraj; Nasani, Narendar; Pukazhselvan, D.; Fagg, Duncan P.
• Is Part Of: International journal of hydrogen energy. Volume 44:Number 59(2019)
• Page Start: 31466
• Page End: 31474
• Publication Date: 2019-11-29
• Subjects: Solid oxide fuel cells -- Solid oxide electrolyzer cells -- Buffer layers -- Mixed conductors -- Ceria -- Polarization resistance; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2019.10.008
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: The present study is focused on the extension of electrochemically active sites in oxygen electrodes for solid oxide fuel cells (SOFC) or electrolyser cells (SOEC), at the same time as preventing degradation, by the introduction of thin mixed ionic electronic conductive buffer layer materials between electrode and electrolyte. The performance of a Nd2 NiO4 electrode material with YSZ electrolyte was studied with a mixed conducting, Ce0·8 Tb0·2 O2-δ, buffer layer material and compared to that of a more typical approach using a predominately ionic conducting buffer layer, Ce0.8 Gd0.2 O2-δ . Each buffer layer and oxygen electrode were coated on YSZ electrolytes by spin-coating. The chemical reactivity of oxygen electrode, buffer layer and electrolyte sintered powders were analysed by the X-ray diffraction technique. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy analysis (EDS) revealed that spin coated layers have good adhesion, are continuous and offer very good chemical compatibility. Impedance spectroscopy under a range of applied DC bias was used to analyze the contribution of the buffer layer materials under SOFC and SOEC operational modes. The cell with the buffer layer that offers mixed conduction significantly reduces the total electrode polarization resistance across the whole of the studied temperature range (600-850 °C) by around an order of magnitude when compared to an otherwise identical cell without the buffer layer. In comparison, only half of this performance increase can be obtained for a predominantly ionic buffer layer. The critical nature of mixed conductivity in the buffer layer to maximize performance is further reinforced by comparison of current results to the literature performance of another mixed conducting buffer layer, Ce0.8 Pr0.2 O2-δ . Highlights: Formation of Ce0.8 R0.2 O2-δ + 2 mol% Co buffer layers (R = Gd, Tb) on YSZ electrolytes with Nd2 NiO4+δ electrodes. Dramatic decreases in polarization resistance, Rp, of up to an order of magnitude, in order, Tb << Gd < no buffer layer. Improved performance associated to increased ambipolar conductivity in the mixed conducting buffer layer. Improved performance maintained on anodic and cathodic polarization.