Electrochemical Performance of Plasma Sprayed Metal Supported Planar Solid Oxide Fuel Cells

Abstract

High production cost is one of the major barriers to widespread commercialization of solid oxide fuel cells (SOFCs). Thermal spray techniques are a low cost alternative for the production of SOFCs. The objective of this work was to evaluate the electrochemical performance of cells produced by plasma spraying. The anode was deposited on a porous metallic support by atmospheric plasma spraying (APS) whereas the electrolyte was deposited by plasma spray-thin film (PS-TF) technique, which can produce thin and dense coatings at high deposition rates. The cathode was deposited by screen-printing and in-operando sintering. The electrochemical tests were performed at 650-800 • C. Current-voltage characteristics and impedance spectra were measured and analyzed. The impact of electrolyte composition and layer thickness on the gas tightness of the electrolyte and the area specific resistance of the cell is discussed. The results show that the applied thermal spraying techniques are a potential alternative for producing SOFCs. Solid oxide fuel cell (SOFC) is a promising technology for producing electricity by clean energy conversion through an electrochemical reaction of fuel and air. High production costs of the cells are still a major obstacle in the widespread commercialization of SOFCs, despite the use of this technology in different areas of energy conversion such as combined heat and power (CHP) generation for residential applications, distributed energy production and auxiliary power units (APUs). 1An approach to reduce costs and improve durability is to use a cost-effective metal supported cell structure. The usage of metal supported cells (MSCs) brings the advantage of high electrical and thermal conductivity, superior toughness and higher thermal shock resistance, better workability, and shorter start-up times as compared to the state-of-the-art anode-supported cells (ASCs).2 Since ferritic stainless steel is significantly cheaper than typical electrode and electrolyte materials, using steel for the mechanical support of the cell can lower the cost substantially.3 So, in addition to superior properties, MSCs would also result in lower per unit cost.During recent years, the redox instability of ASCs in case of fuel supply interruption at high temperature has been identified as a major issue for long term reliability of SOFC stacks in operation. 4,5 The instability occurs due to reoxidation of nickel in the anode to nickel oxide, which results in at least 40% volume increase leading to catastrophic cell/stack failure. Even though a few ways of reducing or avoiding this instability in ASCs have been proposed, these ways add cost and complexity to the SOFC system and cannot necessarily be considered reliable and robust, especially taking the risk into account that a complete failure of system could occur.4,5 Hence, redox stability in ASCs is still a key concern. Due to mechanical strength provided by the steel substrate and a thinner anode in MSCs, these cells are highly robust and much more reliable in case of fuel s...

Solid oxide cell electrolytes deposited by atmospheric suspension plasma spraying at high velocity and high temperature

“…Note that the peak at ∼10 kHz is not considered here, as it may be an artefact of the limited measurement range. Numerous studies have employed DRT on SOCs [34,[49][50][51][52][53][54][55] and to a lesser extent, metal-supported SOCs [56][57][58][59][60] to deconvolute electrochemical processes. Based on this prior work and gas dilution testing, we hypothesize that the processes at 5-8 and 20-40 Hz and are ascribed to the air electrode, while the processes at 0.5-1, 200-300, and 2000-4000 Hz are ascribed to fuel electrode.…”

“…In this work, the peak height at 20-40 Hz decreased for EIS measurements at increased current density, but the process remained as the dominant R p contribution. Another possible degradation mode is the formation of an SrZrO 3 interlayer between the YSZ and LSCF layers as a result of the lack of a GDC protective layer [53,58]. Kromp et al [58] studied SrZrO 3 interlayer formation using DRT at 650 • C on Fe-Cr|YSZ-Ni-GDC|ScYSZ|LSCF-GDC cells with and without a protective GDC layer.…”

Magnetron deposition of yttria-stabilised zirconia electrolyte for solid oxide fuel cells

“…In order to reduce the operating temperatures to (400-650) o C , formation of electrolyte with the thickness of several hundred nanometers is needed [6]. Traditional well-studied methods of electrolyte formation are various powder technologies, such as slip casting [7], screen printing [8], electrophoretic deposition [9], plasma spraying [10] and others. Despite the relative simplicity and low cost of these methods, they are designed for creation of thick coatings (tens of micrometers and higher) and are not suitable for formation of thin films.…”

The Effect of Fuel Electrode Roughness On the Properties of Plasma Sprayed Solid Oxide Cells

“…Previous work has shown that the electrode surface roughness prior to deposition of the electrolyte has a strong influence on electrolyte leak rates and OCVs (4,5). The effect of electrode surface roughness on electrolyte permeability is more pronounced on electrolytes deposited by suspension plasma spraying (SPS), as compared with other techniques (6). Some degree of surface roughness is important for coating adhesion (7,8), but when the asperities are too large (e.g.…”