Evaluation of lanthanum tungstates as electrolytes for proton conductors Solid Oxide Fuel Cells

摘要

La27W4NbO55-delta (LWNO) has been tested as electrolyte for proton conductor Solid Oxide Fuel Cells (PC-SOFCs). For this purpose, different electrodes and composite electrodes are considered, including: La0.8Sr0.2MnO3-delta, La0.6Sr0.4Co1-xFexO3-delta, La0.75Sr0.25Cr0.5Mn0.5O3-delta, SrFe0.75Nb0.25O3-delta and NiO. Chemical compatibility between the cell components is investigated by X-ray powder diffraction (XRPD) and energy dispersive spectroscopy (EDS). Furthermore, area specific resistance (ASR) for the different electrodes is determined in symmetrical cells by impedance spectroscopy. XRPD and EDS analysis does not reveal significant bulk reactivity between most of these electrodes and LWNO electrolyte in the typical operating temperature range of an SOFC (600-900 degrees C). However, minor interdiffusion of elements at the electrolyte/electrode interface has negative effects on both the ohmic losses and electrode polarization of the cells. ASR values are significantly improved by using a porous buffer layer of Ce0.8Gd0.2O1.9 (CGO), deposited between the electrolyte and electrode materials, to prevent reactivity. A single cell with a 350 mu m-thick electrolyte, NiO-CGO and La0.6Sr0.4Co0.8Fe0.2O3-delta-CGO composite as anode and cathode, respectively, generates maximum power densities of 140 and 18 mWcm(-2) at 900 and 650 degrees C, respectively. (C) 2015 Elsevier B.V. All rights reserved.