News Source: School of Chemistry and Chemical Engineering

Editor: Duan Kailong

Translator: Hou Bingqing, News Agency of BIT

Recently, new progress has been gained in designing oxygen electrode materials for solid oxide fuel cells by the teams of Wang Zhenhua and Sun Kening, professors from School of Chemistry and Chemical Engineering of Beijing Institute of Technology. Related research results are published in ACS Energy Letters, the energy flagship journal of American Chemical Society, under the title “In Situ Self-Reconstructed Nanoheterostructure Catalysts for Promoting Oxygen Reduction Reaction” that has been selected as the cover article. BIT is the only corresponding author affiliation. Prefossor Wang Zhenhua and Professor Sun Kening from School of Chemistry and Chemical Engineering are corresponding authors, and Yu Xiaodan, doctoral candidate of class 2021 from School of Chemistry and Chemical Engineering, is the first author.

Solid Oxide Fuel Cells(SOFCs) is an all-solid ceramic energy conversion device which can directly convert chemical energy into electrical energy. With the such advantages as high efficiency of energy conversion, strong fuel adaptability and low pollution emissions, it has broad application prospects in distributed power stations, auxiliary power supply for vehicles, household combined heat and power(CHP) and military use. In SOFCs, cathode, as a core material, plays a decisive role in the cell’s output performance and lifespan. However, the slow Oxygen reduction reaction(ORR) on the oxygen electrode has always constrained the commercialization of medium and low temperature SOFCs. Therefore, the development of cathode materials with higher catalytic activity is the current focus of SOFC researches.

This research developed an in-situ self-constructing heterointerface method different from the traditional composite method. Nanosized cobalt/iron alloy precipitates with A-site deficient (Pr0.4Sr0.6)0.95Co0.2Fe0.8O3-δ(short for PSFC) in a reducing atmosphere, and then it is oxidized to cobalt/iron nanospinel to form Pr0.4Sr0.6Co0.2Fe0.8O3-δ-(CoxFe1-x)3O4 (short for sp-PSFC) as a heterostructure of in-situ composite nanospinel on perovskite surface. The precipitation of nanospinel causes lattice distortion and electronic reconstruction at heterointerface, which reduces the oxygen adsorption energy on the surface and raises the surface oxygen exchange rate; the formation of tensile strain reduces the orbital hybridization between cobalt and iron, making the formation energy of oxygen vacancies reduced; at the same time, the precipitation of cobalt and iron leads to the expansion of the oxygen migration space in the bulk phase, and the interaction on the migration path is reduced, which provides more transport channels for the bulk oxygen ions and accelerates the oxygen migration. This study verified the effect of heterostructure on electron reconfiguration and oxygen ion migration, which plays an important role in promoting the development of oxygen electrode materials with high catalytic performance.

Figure 1. Characterization and mechanism of oxygen reduction process in sp-PSFC heterojunction. (a) Temperature programmed desorption. (b) Thermogravimetric and iodometric titration. (c) Surface oxygen exchange rate. (d) Oxygen adsorption energy calculated using first-principles calculations. (e) and (f) Single-phase materials Schematic diagram of the structure and oxygen reduction mechanism of PSFC and composite heterostructure material sp-PSFC.

This research is supported by the National Natural Science Foundation of China（22078022、22178023、22179007）and the Beijing Key Laboratory of Chemical Power Source and Green Catalysis.

Link of the paper:https://doi.org/10.1021/acsenergylett.2c01249

Introduction of the first author:

Yu Xiaodan graduated with a bachelor’s degree from Nanjing University of Science and Technology in 2017, got a master’s degree in chemical engineering and technology from Beijing Institute of Technology in 2020, worked for Weichai Power Co., Ltd from 2020 to 2021, and has been studying for a doctorate in BIT since 2021. He mainly engaged in the development of the electrode material for SOFCs and the development of flat-tube fuel cell systems. He has also published 2 SCI papers as the first author in ACS Energy Letters and ACS Applied Energy Materials, and joined in many key R&D projects.