Abstract
The electrode microstructural properties significantly influence the efficiency and durability of many electrochemical devices including solid oxide fuel cells. Despite the possibility of simulating the electrochemical phenomena within real three-dimensional microstructures, the potential of such 3D microstructural information has not yet been fully exploited. We introduce here a completely new methodology for the advanced characterization of inhomogeneous current distribution based on a statistical analysis of the current of each particle within the microstructure. We quantify the large variation in local current distribution and link it to the particle size dispersion, indicating how particle coarsening can trigger further degradation. We identify two classes of particles: those transferring more current than average, which show 10–40% more particle-particle contacts, and those producing more current than average, characterized by ∼2.5 times larger three-phase boundary length per unit volume. These two classes of particles are mutually exclusive, which implies that up to the 30% of the electrode volume within the functional layer is underutilized. This fundamental insight goes well beyond the predictions of continuum modeling, allowing us to revisit the current standards regarding safe operating conditions and to suggest alternative strategies based on nanoparticle infiltration, template-assisted synthesis and additive manufacturing for designing more durable electrodes.
Highlights
The twenty-first century is expected to witness the transition from the abundant use of fossil fuels to a clean and sustainable energy economy based on renewable resources [1]
The electrode under consideration is a porous solid oxide fuel cells (SOFCs) anode made of Ni and scandia-stabilized zirconia (ScSZ), operating at 973 K in 97% H2–3% H2O gas mixture [50,51], wherein the following electrochemical reaction: H2(g) + O(2S−cSZ) → H2 O(g) + 2e(−Ni) is assumed to occur at the three-phase boundaries (TPBs) between the Ni, ScSZ and pore phase
This paper presented the potential of an innovative methodology to perform the advanced three-dimensional characterization at the particle level in porous electrodes
Summary
The twenty-first century is expected to witness the transition from the abundant use of fossil fuels to a clean and sustainable energy economy based on renewable resources [1] In this scenario, electrochemical energy conversion and storage, as provided by fuel cells and Journal of Power Sources 396 (2018) 246–256 batteries, will play a prominent role [2,3]. The electrochemical behavior of the electrodes has been interpreted using macro-homogeneous models [12,13,14,15,16], which describe the conservation and transport of charged and chemical species in 1D or 2D by assimilating the porous microstructure to a homogeneous continuum, with averaged microstructural properties represented by effective transport and geometrical parameters [17,18]. Such effective microstructural properties were estimated only by using percolation models [19,20] until 3D tomography enabled the reconstruction of the real electrode microstructure [21,22,23,24,25]
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