Effect of Nanoparticle Impregnation on Ni-YSZ Cermet Electrode Polarization Using YSZ-Supported Cells

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Impregnation of nanoparticles is a solution for increasing the electrocatalytic performance of Ni-yttria stabilized zirconia (YSZ) cermet electrodes in solid oxide fuel cells (SOFCs) and electrolysis cells. The electrocatalytic activity is related to the density of triple phase boundaries (TPBs) within the active layer of the cell. Within the anode active layer (AAL), the TPB density is limited by the feature size of the Ni-YSZ scaffold, which is on the order of microns. Impregnation of nickel nanoparticles with diameters of less than 100 nanometers within the AAL has been shown to improve electrocatalytic activity. However, there is a trade-off between the volume of impregnated nickel particles and the pore volume within the electrode. Infiltration reduces pore volume, slowing gas-phase mass transfer within the AAL and increasing concentration polarization. Another consideration is that impregnated nanoparticles are effective only if they are electrically connected to the Ni-YSZ scaffold. In this work, the impregnation of a second phase is used to fulfill two objectives: anchoring the nickel nanoparticles to prevent coarsening, and providing an electrical path from the nanoparticles to the scaffold. The goal of this study is to find the best electrode performance by comparing cell polarizations while varying nanoparticle impregnation parameters to control nickel loading and nickel particle size. Electrode polarization is measured using EIS on impregnated symmetric cells supported on YSZ substrates in a single atmosphere chamber, at varying gas compositions and temperatures. The microstructure of impregnated electrodes is quantified using analysis of SEM fracture cross-sections. By correlating the morphology of impregnated electrodes with electrode polarization, an optimal procedure for the impregnation of nickel nanoparticles into Ni-YSZ cermet electrodes can be determined for use in anode-supported Ni-YSZ SOFCs.