Bifunctional Ce0.9Gd0.09M0.01O2−δ (M = Fe, Cu) interlayers with micro-doping for high-performance solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are promising, sustainable and efficient electrochemical energy conversion devices. The dense and thin interlayer prepared at low sintering temperature is essential to avoid detrimental reaction between cobalt-containing cathode and zirconia-containing electrolyte. The co-doping of transition metal ion and Gd3+ in ceria is an available new method to reduce the densification temperature, while have a negative effect on the electrical performance. Herein, a strategy of micro-doping for bifunctional Ce0.9Gd0.09M0.01O2−δ (M = Fe, Cu) interlayers is proposed to achieve excellent sintering performance and electrochemical performance. The results indicate that adequate liquid phase production and lattice doping could simultaneously increase the relative density at lower sintering temperature and improving the electrical conductivity of interlayers. 1 mol.% Cu micro-doping could reduce the sintering temperature by 350 °C, make the relative density up to be 96.26%, and the electrical conductivity of 600 °C up to be 0.0134 S/cm. The single cell with Ce0.9Gd0.09Cu0.01O2−δ (GCDC) interlayer has the low ohmic resistance of 0.31 Ω cm2, and exhibits a high maximum power density of 0.745 W cm−2 at 750 °C, which was higher than 0.603 W cm−2 of the single cell with undoped GDC interlayer.