3-D inkjet printed solid oxide electrochemical reactors III. Cylindrical pillared electrode microstructures

Inkjet printing is a scalable technique that can fabricate customised three-dimensional microstructures, reproducibly, accurately, and with high material utilisation, by printing multiple layers sequentially onto previously printed layers, to produce architectures tailored in this case to electrochemical reactors. Printable yttria-stabilised zirconia (YSZ) and lanthanum strontium manganite (LSM) inks were formulated to enable fabrication of solid oxide electrochemical reactors (SOERs): H2O-H2 | Ni(O)-YSZ | YSZ | YSZ pillars | LSM | O2. Of the geometries studied, equi-sized, hexagonally-arranged cylindrical pillars were predicted to produce the largest ratio of interfacial to geometric (cross-sectional) areas. However, this neglects effects of potential and current density distributions that constrain up-scaling to more modest factors. Hence, using kinetic parameter values from the literature, finite element computational simulations of the pillared SOER in (H2 - O2) fuel cell mode predicted peak power densities of 0.11 W cm−2 at 800 °C, whereas its counterpart with only a planar electrolyte layer produced only 0.05 W cm−2; i.e. the pillars were predicted to enhance peak power densities by ca. 2.3. Arrays of several thousand YSZ cylindrical pillars were printed, with post-sintering diameter, height, and spacing of 25, 95 and 63 μm, respectively. LSM was inkjet-printed onto the pillars, and sintered subsequently, to produce contiguous films ca. 4 μm thick. In (H2 - O2) fuel cell mode at 725, 770, and 795 °C, these reactors produced peak power densities of 0.09, 0.21, 0.30 W cm−2, respectively, 3–6 times greater than the performance of ‘benchmark’ Ni(O)-YSZ | YSZ | LSM reactors inkjet-printed with planar cathodes operating under the same conditions, thereby demonstrating the benefit of inkjet printing as a fabrication technique for SOERs.