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Funding Information: This study was supported by National Natural Science Foundation of China (NSFC) under grant no. 11674086, 11904088, and 2019CFB183. Scientific Research Project of Education Department of Hubei Province (no. Q20191010) and Research Project of Wuhan Science and Technology Bureau (no. 2019010701011394). Dr. Asghar thanks the Hubei Talent 100 program and Academy of Finland (Grant nos. 13329016, 13322738) for their support. Publisher Copyright: © 2021 The Authors. Published by American Chemical Society. Formation of a heterostructure of semiconductor materials is a promising method to develop an electrolyte with high ionic conductivity at low operational temperature of solid oxide fuel cells (LT-SOFCs). Herein, we develop various heterostructure composites by introducing a pure ionic conductor Sm0.2Ce0.8O2-δ (SDC) into a semiconductor LiNi0.8Co0.15Al0.05O2 (LNCA) for LT-SOFCs electrolyte. The morphology, crystal structure, elemental distribution, micro-structure, and oxidation states of the composite of LNCA-SDC are analyzed and studied via X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), high energy dispersive spectrometry, and X-ray photoelectron spectroscopy (XPS). Electrochemical studies found that the optimal weight ratio of 0.5 LNCA-1.5 SDC heterostructure composite exhibits relatively high ionic conductivity (0.12 S cm-1 at 520 °C), which is much higher than that of SDC. The designed composite of LNCA-SDC heterostructures with optimal weight ratio (0.5:1.5) delivers a remarkable fuel cell power output of 0.735 W cm-2 at 520 °C. The formation of the heterostructure and reconstruction of energy bands at the interface play the crucial roles in enhancing ionic conduction to improve electrochemical performance. The prepared composite heterostructure delivers a unique and insightful strategy of electrolyte in advanced LT-SOFCs.

Tuning semiconductors as an electrolyte for advanced low-temperature fuel cells is an exciting but challenging research subject. To realize this, we develop the cobalt-doped SrSnO3 (SrCo0.1Sn0.9O3−...

Interface engineering holds huge potential for enabling exceptional physical properties in heterostructure materials via tuning properties at the atomic level. In this study, a heterostructure built by a new redox stable semiconductor SrFe0.75Ti0.25O3-δ (SFT) and an ionic conductor Sm0.25Ce0.75O2 (SDC) is reported. The SFT-SDC heterostructure exhibits a high ionic conductivity >0.1 S/cm at 520 °C, which is 1 order of magnitude higher than that of bulk SDC. When it was applied into the fuel cell, the SFT-SDC can realize favorable electrolyte functionality and result in an excellent power density of 920 mW cm-2 at 520 °C. The prepared SFT-SDC heterostructure materials possess both electronic and ionic conduction, where electron states modulate local electrical field to facilitate ion transport. Further investigations to calculate the structure and electronic structure/state of SFT and SDC are done using density functional theory (DFT). It is found that the reconstruction of the energy band at interfaces is responsible for such enhanced ionic conductivity and cell power output. The current study about the perovskite-based heterostructure presents a novel strategy for developing advanced ceramic fuel cells.