Synergetic proton conduction in BaZr0.8Y0.2O3-δ–carbonate composite electrolyte for intermediate-temperature solid oxide fuel cells

Abstract

In the present study, electrical properties of a composite electrolyte composed of a BaZr 0.8 Y 0.2 O 3-δ (BZY) and a perspective of defect chemistry. A DFT first-principles calculation further confirmed that proton transfer in molten carbonates was a low-energy process.

Proton Transfer in Molten Lithium Carbonate: Mechanism and Kinetics by Density Functional Theory Calculations

“…Therefore, there are possible uncertainties in the calculated energetics. To verify and correct such possible errors, we have re-examined the energies from local structures extracted from the cluster and the revised values showed large improvements and better consistency with current FPMD results and previous experimental results 17 . In addition, long range interactions in the molecular system were estimated by CAM-B3LYP 46 , but no significant difference was observed.…”

“…The final energy barrier from DFT is 8.0 kcal/mol, which is in a good agreement with the activation energy of 7.5 kcal/mol from FPMD simulations. The activation energy was measured to be 7.6 kcal/mol using a BZY/MC composition electrolyte at 600 °C and MC was considered as the main conducting media for protons 17 . Based on those values, we can conclude that the energy barrier for the migration of proton in molten lithium carbonate salt is in the range of 7.5–8.0 kcal/mol and excellent consistency between DFT modeling and experimental measurement was observed.…”

“…More recently, Huang et al . 16, 17 reported that densification of BZY can be promoted by adding molten carbonate (MC) as a sintering aid. MC was filled into the pores of BZY first by infiltration method.…”

“…25. In fact, the effect of water on the proton conductivity was already examined independently by two different groups 17, 19 . Both reported that the conductivity was increased by only 6–8% when water partial pressure changes from 0 atm to 0.3 atm in 5% H 2 Ar or N 2 .…”

“…The calculated energy barrier was 0.34 eV along the direction of [001]. However, the experiments in refs 16 and 17 have shown that the MC phase only have large contributions to the ionic conductivity when it is melt at higher temperature than 450 °C. This implies that the results in ref.…”