3-D Inkjet Printed Electrode Microstructures for Solid Oxide Electrolysers and Fuel Cells

Increasing contributions of renewable energy sources to electrical power grids necessitates the development of advanced energy storage technologies. Reversible high temperature solid oxide electrochemical reactors are one possible solution, whereby surplus electrical energy can be converted into chemical energy in electrolyser mode and re-converted into electrical energy in fuel cell mode as power demand peaks. Increasing the densities of triple phase boundaries (electrode | electrolyte | reactant gases in pores) at which the electrochemical reactions occur, increases energy conversion efficiencies of solid oxide fuel cells (SOFCs) and electrolysers (SOEs). Electrode structures based on infiltrated-scaffolds have enhanced triple phase boundary densities and better pore size control than those from conventional fabrication methods such as powder mixing. However, fabricating scaffolds reproducibly and predictably at micrometre scales is challenging. Hence, we used a 3D inkjet printer (Ceradrop X-Series) with three multi-nozzle print heads, to produce scaffolds with achievable feature size resolutions of ca. 30 μm in the horizontal plane and 1 μm in the vertical direction (Figure 1A). For printing SOFCs and SOEs, we developed a printable yttria-stabilised zirconia (YSZ) colloidal dispersion (‘ink’) with sub-micrometre precursor particles. This ink was used to print gas-tight YSZ electrolytes ca. 8 mm thick onto ‘green’ NiO-YSZ substrates, on top of which we printed arrays of micro-pillars with ca. 100-120 μm diameter. The printed cells were heat treated at 600 °C to combust organic additives stabilising particles against aggregation, followed by sintering at 1500 °C. The micro-array was then infiltrated with a 1 molar aqueous nitrate precursor solution of La0.8Sr0.2MnO3- δ(LSM). Following multiple infiltrations and decomposition of nitrates at 500 °C, the entire cells were calcined at 1100 °C to form the LSM positive electrode (Figure 1B). Electrochemical performances of these cells with tailored microstructures will be presented for electrolyser and fuel cell modes, for various operating temperatures and gas mixtures (e.g. CO2, H2O, CO, H2). Figure 1