Three-dimensional reconstruction of a solid-oxide fuel-cell anode

Abstract

The drive towards increased energy efficiency and reduced air pollution has led to accelerated worldwide development of fuel cells. As the performance and cost of fuel cells have improved, the materials comprising them have become increasingly sophisticated, both in composition and microstructure. In particular, state-of-the-art fuel-cell electrodes typically have a complex micro/nano-structure involving interconnected electronically and ionically conducting phases, gas-phase porosity, and catalytically active surfaces. Determining this microstructure is a critical, yet usually missing, link between materials properties/processing and electrode performance. Current methods of microstructural analysis, such as scanning electron microscopy, only provide two-dimensional anecdotes of the microstructure, and thus limited information about how regions are interconnected in three-dimensional space. Here we demonstrate the use of dual-beam focused ion beam-scanning electron microscopy to make a complete three-dimensional reconstruction of a solid-oxide fuel-cell electrode. We use this data to calculate critical microstructural features such as volume fractions and surface areas of specific phases, three-phase boundary length, and the connectivity and tortuosity of specific subphases.

Phase wettability and microstructural evolution in solid oxide fuel cell anode materials

“…Additionally, use of the phase-field method at the mesoscale affords the spatial resolution required to capture the heterogeneous nature of the anode while still accessing the time scales necessary to observe long-term degradation mechanisms [7]. Previous computational studies of SOFC anodes using the phase-field method have displayed results in accordance with experimental observations [17][18][19][20].…”

“…As usual, the starting point of our diffuse-interface approach is the introduction of order parameters (OPs) that describe each phase in porous SOFC cermets [17][18][19][20]. Next, a thermodynamic free energy F tot is constructed in terms of the OPs, whose spatiotemporal evolution follows from the minimization of F tot .…”

Modeling and comparison to literature data of composite solid oxide fuel cell electrode–electrolyte interface conductivity

“…The effects of these processes and the various features of the raw materials on fuel cell performance have been investigated through many previous studies by empirical methods and the development and application of models [9][10][11][12][13][14]. Experimentalists have identified many parameters that are important to manufacturing electrode-electrolyte interfaces with low ohmic and/or activation losses.…”

“…Dusastre and Kilner have demonstrated the benefits of including multipurpose materials such as mixed electronic-ionic conductors (MEIC) [13]. A recent visualization study by Wilson et al [14] has begun to provide mechanistic insights through investigation of the electrode microstructural and compositional parameters such as tortuosity, interfacial adhesion, and interconnectivity in an effort to provide greater insight and improved detail with regard to these factors and how they affect percolation in the electrode. Reaction mechanisms involved in surface exchange and transport phenomena at an SOFC cathode [22].…”

Chemomechanics of ionically conductive ceramics for electrical energy conversion and storage

“…A variety of tomographic methods have been applied to battery electrodes to better understand these complex heterogeneous microstructures by facilitating evaluation of porosity, tortuosity, and surface area, and to inform more realistic models of electrode function and failure. X-ray tomography has been used to non-destructively reconstruct composite electrodes [39,40] [42,43]. Clague et al converted this 3-D structure into a mesh for finite element (FE) simulation of stresses developing within the material as temperature increased.…”