Solid Oxide Fuel Cells with laser-patterned electrode-electrolyte interfaces

Abstract

Solid Oxide Fuel Cells (SOFC) are electrochemical devices that transform hydrogen into electricity with high efficiency and zero emission of pollutants. As they work at high temperature, they don’t need expensive catalysers and can also be fuelled with hydrocarbons, because the waste heat can be used for fuel reforming. The cells are formed by a tight solid oxide electrolyte and two porous electrodes. A typical cell configuration is an yttria-stabilised zirconia (YSZ) electrolyte, a Ni-YSZ fuel electrode and an YSZ-LSM (LSM: La1-xSrxMnO3) oxygen electrode. As cathode activation polarisation is one of the main contributions to the losses of a Solid Oxide Fuel Cell, we use pulsed laser ablation to produce patterned electrode-electrolyte interfaces. Cathodic polarisation depends on the length of the triple-phase boundary (TPB) region, where the electrochemical reactions takes place. Thus, laser patterned interfaces with increased electrolyte-electrode contact surface can present electrochemical enhanced properties. In this work we have used a computer-controlled laser beam emitting at λ=532 nm (green region) and with 5 ns pulse width. We marked different micro-patterns, square and hexagonal arrays, on YSZ plates and prepared LSM-YSZ/YSZ/LSM-YSZ symmetrical cells to determine their activation polarisation by Electrochemical Impedance Spectroscopy (EIS). To get good contact after sintering the electrode on the patterned electrolyte, as well as appropriate electrode microstructure, it was necessary to adjust the ceramic deposition procedure and to use pressure-assisted sintering with low loads. Patterned cells show an improvement in the cathodic activation processes. The decrease in polarisation with respect to unprocessed ones is about 30%. Further studies are in progress to increase the contact surface and reduce the polarization.