Leakage Current and Chemical Potential Profile in Proton-Conducting Bi-Layered Solid Oxide Electrolyte with BZY and Hole-Blocking Layers

Abstract

Solid oxide fuel cells (SOFCs) with proton-conducting solid electrolyte, instead of the oxide-ion conducting solid electrolyte have attracted attentions because of their high potential to reduce operating temperatures and to enhance the electrical efficiencies of SOFCs. In addition, the proton-conducting SOFCs with multistage electrochemical oxidation configuration will be promising technology for critically-high electric efficiencies. However, it is known that there are non-negligible charge -carriers other than protons in typical proton-conducting solid oxide electrolytes at relatively high temperatures. The existence of the partial conductivities of holes and/or electrons will cause the internal leakage current that consumes fuel but never generates any electrical power output. The higher ratio of the leakage current to external current will more deteriorate the electrical efficiency. In this study, the effects of blocking -layers formed on the air side surface of base electrolyte layer consisting of BaZr0.8Y0.2O3-δ (BZY82) for suppressing the leakage current have been investigated by using electrochemical parameters of the partial conduction of the materials. The chemical potential profile and leakage current showed large dependence on the material of the blocking -layer. Lanthanum tungstate was found to play a role as unique and strong blocking -layer against the leakage current.

Three-dimensional multiphysics coupling numerical simulation of a proton conductor solid oxide fuel cell based on multi-defect transport

“…Although BZY is used as the electrolyte material in this study, the model framework is also applicable to mixed-conducting ceramic fuel cells and electrolytic cells with other electrolyte materials, such as SrCe 1− x Yb x O 3 , 19 SrZr 1− x Y x O 3− δ 40 and La 28− x W 4+ x O 54+ δ . 41 There are also multiple defect transport phenomena in these materials. Moreover, although hydrogen is used as fuel in this paper, the model can also be further developed to study other H-SOFCs fueled by hydrocarbons and ammonia.…”

Proton conductivity of Li+–H+ exchanged Li7La3Zr2O12 dense membranes prepared by molten long-chain saturated fatty acids

“…[21][22][23] Unlike perovskite-type oxides, alkali-proton-exchanged oxides suffer less from electronic current leakage under high oxygen potentials because the proton is incorporated by ion exchange, not by the hydration of oxygen vacancies introduced by acceptors. 24,25 The alkali-proton exchange technique provides an outstanding possibility for producing a wide variety of proton-conducting oxides with a skeleton of excellent alkali-ion conductors, some of which may show high proton conductivities at intermediate temperatures with reasonable chemical stability.…”

Bilayer Cell Model and System Design of Highly Efficient Protonic Ceramic Fuel Cells

“…In previous studies, lanthanum tungstate, La28-xW4+xO54+3x/2v2-3x/2 with a La/W ratio of 6.7 (LWO) was successfully used as a hole-blocking layer in a bilayer electrolyte to suppress leakage current (1)(2)(3). Additionally, it was shown that a bilayer electrolyte, made of BaZr0.8Yb0.2O3−δ (BZYb) and BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb), can reduce the interfacial resistance between the cathode and the electrolyte and can also prevent nickel diffusion from the anode due to high-temperature cell fabrication processing (4).…”