Electrochemical study on Ce0.85Sm0.15O1.925–BaCe0.83Y0.17O3− composite electrolyte

The composites of Ce0.85Sm0.15O1.925 (SDC) and BaCe0.83Y0.17O3−δ (BCY) are investigated as electrolytes for solid oxide fuel cells (SOFCs). The electrolyte materials SDC and BCY are synthesized by the glycine–nitrate route and the sol–gel process, respectively. Composite electrolytes are then prepared by mixing SDC and BCY in weight ratios of 9:1 (SB91), 8:2 (SB82), 7:3 (SB73) and 5:5 (SB55). Results from X-ray diffraction (XRD) demonstrate that Sm3+ can diffuse from SDC to BCY. The SEM results reveal that the average grain size decreases with increasing BCY content. Impedance spectroscopy measurements reveal that the grain boundary resistance can be significantly reduced by adding 10–20 wt.% BCY to SDC. Among all of the samples, SB91 exhibits the lowest total resistance. In the impedance spectra of SB73 and SB55, two grain boundary responses can be identified. Compared with SDC and BCY, the composite electrolytes exhibit lower electrode interfacial polarization resistances. Single cells based on the electrolytes are fabricated using Ni0.9Cu0.1Ox/SDC as anode and LaSr0.25Ba0.75Co2O5+δ as cathode. The cell based on SB91 electrolyte exhibits the lowest total resistance under open circuit conditions and the maximum power density of the cell based on SB91 electrolyte reaches 0.495 W cm−2 at 800 °C.