Enhanced proton conductivity and CO2-tolerance of intermediate-temperature protonic ceramic fuel cell with lanthanum tungstate-based composite cathode

Despite the low activation energy for proton diffusion under protonic ceramic fuel cell (PCFC) operation, the high-performance PCFC is still limited by the low proton conductivity of most cathode materials. A decrease in cathode acidity can enhance proton affinity; however, the severe CO2-tolerance associated with the doping of alkaline earth metals in perovskite oxides is also a challenge. Herein, a proton conducting oxide La5.5W0.45Mo0.4Nb0.15O11.25-δ (LWMN), which possesses excellent chemical stability under a CO2-containing atmosphere, is composited with Sr2Sc0.1Nb0.1Co1.5Fe0.3O6-δ (SSNCF) as the PCFC cathode. A 3 wt% alkali earth ion-free oxide LWMN composite in the cathode material can strengthen proton diffusion while weakening CO2 adsorption. Thus, in wet air containing CO2, the symmetrical cell based on the 3 wt% LWMN-SSNCF achieved a linear degradation rate of ASRs of 1.33 × 10−3 Ω cm2 min−1 for the first 3 h, which was lower than the 2.15 × 10−3 Ω cm2 min−1 achieved by the symmetrical cell based on the single-phase SSNCF cathode. Furthermore, the PCFC based on the composite cathode shows an improved performance of 1.114 W cm−2 at 650 °C due to its superior proton conduction. This strategy endowed the cathode with superior proton diffusion as well as low CO2 adsorption.