Modulating the Energy Band Structure of the Mg-Doped Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δElectrolyte with Boosted Ionic Conductivity and Electrochemical Performance for Solid Oxide Fuel Cells

Funding Information: This work was supported by the National Natural Science Foundation of China (52105582), the Natural Science Foundation of Guangdong Province (grant no. 2020A1515011555), the High-Talent Research Funding (827-000451), the Fundamental Research Foundation of Shenzhen (JCYJ20210324095210030), the Open Foundation of the State Key Laboratory of Digital Manufacturing Equipment and Technology (DMETKF2021016), and the National Natural Science Foundation of China (11674085 and 51772080). M.I. Asghar thanks the Hubei overseas Talent 100 programme (as a distinguished Professor at Hubei University) and the Academy of Finland (grant nos. 13329016 and 13322738) for its support. We are thankful to Dr. Ghulam Yasin for proofreading and suggestions. We are really thankful to Dr. Xiuan Xi and Prof. Dr. Xian-Zhu Fu for initially using their GC characterization facilities and their discussion at the College of Materials Science and Engineering, Shenzhen University and then utilizing another GC–MS characterization for further analysis. FAchieving fast ionic conductivity in the electrolyte at low operating temperatures while maintaining the stable and high electrochemical performance of solid oxide fuel cells (SOFCs) is challenging. Herein, we propose a new type of electrolyte based on perovskite Sr0.5Pr0.5Fe0.4Ti0.6O3-δ for low-temperature SOFCs. The ionic conducting behavior of the electrolyte is modulated using Mg doping, and three different Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) samples are prepared. The synthesized Sr0.5Pr0.5Fe0.2Mg0.2Ti0.6O3-δ (SPFMg0.2T) proved to be an optimal electrolyte material, exhibiting a high ionic conductivity of 0.133 S cm-1 along with an attractive fuel cell performance of 0.83 W cm-2 at 520 °C. We proved that a proper amount of Mg doping (20%) contributes to the creation of an adequate number of oxygen vacancies, which facilitates the fast transport of the oxide ions. Considering its rapid oxide ion transport, the prepared SPFMg0.2T presented heterostructure characteristics in the form of an insulating core and superionic conduction via surface layers. In addition, the effect of Mg doping is intensively investigated to tune the band structure for the transport of charged species. Meanwhile, the concept of energy band alignment is employed to interpret the working principle of the proposed electrolyte. Moreover, the density functional theory is utilized to determine the perovskite structures of SrTiO3-δ and Sr0.5Pr0.5Fe0.4-xMgxTi0.6O3-δ (x = 0, 0.1, and 0.2) and their electronic states. Further, the SPFMg0.2T with 20% Mg doping exhibited low dissociation energy, which ensures the fast and high ionic conduction in the electrolyte. Inclusively, Sr0.5Pr0.5Fe0.4Ti0.6O3-δ is a promising electrolyte for SOFCs, and its performance can be efficiently boosted via Mg doping to modulate the energy band structure.Peer reviewe