Upscaling of Co‐Impregnated La_0.20Sr_0.25Ca_0.45TiO₃ Anodes for Solid Oxide Fuel Cells: A Progress Report on a Decade of Academic‐Industrial Collaboration

Abstract

and useful electrical power from a fuel gas (e.g., natural gas), at much higher conversion efficiencies than conventional combustion methods. [1,2] This method of heat and electricity co-generation makes SOFC technology ideal for use in micro-combined heat and power (µ-CHP) units, particularly in the 1-5 kW (electrical power) output class, which may be used to satisfy the total heat and electricity demand of family homes and small businesses. An example of such a unit is the Galileo 1000 N, produced by HEXIS AG between 2013 and 2018. [3] This µ-CHP unit was successfully commercialized with more than 100 units being installed in a variety of locations across Western Europe, each providing 1 kW of electrical power and 20 kW of heat (from an auxiliary burner). [4,5] Currently, the Swiss SOFC manufacturer is focusing on the development of the next-generation SOFC-based µ-CHP unit, designed to provide an increased electrical power output of 1.5 kW at a higher electrical efficiency. [3,6] Typically, high-temperature SOFC (operating at 700-850 °C) are produced using traditional, well-studied, and effective material sets, which have been tailored to suit the requirements of each component. For example, air electrodes (cathodes) are often made from composites of yttria-stabilized zirconia (YSZ) and strontium-substituted lanthanum manganite (LSM) [7][8][9] or composites of cerium gadolinium oxide (CGO) and strontium-substituted lanthanum cobaltite (LSC), [9,10] ferrite (LSF), [11] or cobaltite ferrite (LSCF). [8,[12][13][14][15][16] Electrolytes used in SOFC operating within this temperature regime are zirconia stabilized, commonly, with scandia or yttria (ScSZ or YSZ), [2] while fuel electrodes (anodes) traditionally comprise composites of Ni and either YSZ or CGO. [2,17] However, despite the excellent performance that can be obtained using these materials, there are several challenges posed, specifically, by the anode materials, that must be addressed in order to provide greater resistance to harsh operating conditions in next-generation SOFC systems. These ceramic-metal composites (cermets) of YSZ/CGO and Ni exhibit redox instability, due to the propensity of Ni to agglomerate, in addition to sulfur poisoning and carbon deposition during exposure to unprocessed natural gas feeds. [1,18] Several different materials design approaches have been identified and explored in an attempt to mitigate the limitations of the Solid oxide fuel cell (SOFC) stack technology offers a reliable, efficient, and clean method of sustainable heat and electricity co-generation that can be integrated into micro-combined heat and power (µ-CHP) units for use in residential and small commercial environments. Recent years have seen the successful market introduction of several SOFC-based systems, however, manufacturers still face some challenges in improving the durability and tolerance of traditional Ni-based ceramic-metal (cermet) composite anodes to harsh operating conditions, such as redox and thermal cycling, overload exposure, sulfur poisonin...

Roadmap for Sustainable Mixed Ionic‐Electronic Conducting Membranes

“…[442] If very promising performances have been achieved with perovskite fuel electrode at the button cell level, i.e., ≈1 cm 2 of active area, it is challenging to develop high performance fuel electrode based on perovskite at a stack scale which requires working area of about ≈100 cm 2 . [454] As electronic conductivity level in perovskite fuel electrode is typically in the range 1 -10 S cm −1 it becomes crucial to engineer the electrode to ensure sufficient current collection to compete with nickel cermets that shows conductivity values above 100 -500 S cm −1 . At the stack level the development of highly conducting backbone and contact elements between the fuel electrode and the bi-polar plate with sufficient lateral conductivity is crucial to enable integration of perovskite fuel electrode material into stack.…”

Durability of La0.20Sr0.25Ca0.45TiO3-based SOFC anodes: identifying sources of degradation in Ni and Pt/ceria co-impregnated fuel electrode microstructures

“…Moreover, this reinforces the fact that it is not only the ability of the specific composition of ceria-based component which gives rise to improved/worsened stability of metallic catalyst particles, but rather the interaction and mutualistic relationship between the particular metallic catalyst and ceria-based component, as shown by the stability of SOFC containing Rh/CGO co-impregnated LSCTA-anodes at button cell and short stack scales. 25…”

“…21,23,24 Furthermore, optimisation and upscaling of the Rh/CGO co-impregnated LSCTA-anode to short stack scales at HEXIS has given rise to 'all-oxide' SOFC that rival voltage degradation rates of the current state-of-the-art anode, whilst offering high redox/thermo/thermoredox cycling stability, the ability to operate in sulfur-laden fuel gas and overload stability. 25 In this research, an exploration of the stability of Ni catalyst particles was undertaken, as this catalyst is known to degrade more rapidly than platinum group metals, due to its mobility under reducing conditions, even in impregnated SOFC anodes. Long-term test data is presented for SOFC containing: i) a Ni/CGO impregnated LSCTA− anode and ii) a Ni/CeO2 impregnated LSCTA− anode in order to evaluate the effect of the ceria-based component in 'anchoring' and stabilising the Ni particles on the anode 'backbone', under realistic operating conditions (i.e.…”

Half-Electrolysis of Water with the Aid of a Supercapacitor Electrode

“…The overall cell reaction of water electrolysis is divided into two half-cell reactions, namely, the hydrogen evolution reaction (HER) on the cathode and the oxygen evolution reaction (OER) on the anode. Hydrogen can be fed into fuel cells to generate electricity, − while high-purity oxygen remains a crucial therapy of Covid-19-infected patients . All currently available electrolyzers require a minimum of potable-grade water.…”