Synergistic proton and oxygen-ion transport in fluorite oxide-ion conductor

They published their work on new superionic mechanism in fluorite oxide electrolyte for low temperature protonic ceramic fuel cells  in Energy Material Advances.

"The development of low-temperature and high-performance solid oxide fuel cells is imperative." said corresponding author Dr. Jianbing Huang, Associate Professor of the State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University.

Dr. Huang explained that protonic ceramic fuel cell has several significant advantages as an alternative solid oxide fuel cell operated at low temperature.

"Extensive efforts have focused on enhancing the proton conductivity of oxide ceramic electrolytes in the development of PCFCs. Subsequent studies aimed to improve proton conductivity through structural doping. However, further improvements of electrolyte materials are necessary to achieve higher proton conductivities for efficient PCFC operation."

The development of new structure families of oxide proton conductors as PCFC electrolyte has been widely performed in recent years. According to Dr. Huang, surface/interface proton conduction in fluorite oxides has been successfully applied in semiconductor ionic membrane fuel cells. In this new type fuel cell, surfaces/interfaces of oxide particles will provide proton transport path for low temperature annealing electrolyte.

"In this study, we successfully realize surficial proton transport along oxide-ion conductor GDC particles, achieving a remarkable conductivity of 0.158 S cm^-1 at 500°C." Dr. Huang said, "This conductivity level is several orders of magnitude higher than the ever-reported proton conductivity of nanocrystal/nanofilm GDC associated with water. and even 1-2 orders of magnitude higher than that of the state-of-the-art Ba(Ce,Zr)O₃-based perovskite oxide proton conductors."

"And a synergistic mechanism involving both surface proton conduction and bulk oxygen-ion migration is proposed by comparing electrochemical impedance spectroscopy with distribution of relaxation time (DRT) results of GDC and pure ceria," Dr. Huang said.

According to Dr. Huang, an oxygen vacancy concentration gradient from anode to cathode forms during fuel cell operation. At the same time, oxygen is reduced to oxygen ion (O^2-) by naturally trapping electron and oxygen vacancy at the interface between the cathode and electrolyte. Oxygen ions (O^2-) diffusion is accelerated with the help of a stable drive force caused by the oxygen concentration gradient. At the same time, migration of O^2- in the bulk of GDC particles in an opposite direction to promote H⁺ migration on the GDC particle surface.

The authors believed this finding may provide new insights into the ion transport mechanism on fluorite oxides and open new avenues for advanced low temperatures PCFCs.

Dr. Jianbing Huang, Yong Yu, Xiaomeng Cheng and Prof. Liejin Guo are affiliated with State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University; Other contributors include M.A.K. Yousaf Shah, Hao Wang and Prof. Bin Zhu, Jiangsu Provincial Key Laboratory of Solar Energy Science and Technology/Energy Storage Joint Research Center; Prof. Peter Lund, School of Science, Aalto University.

The Key Project (52336009) and the Basic Science Center Program for Ordered Energy Conversion (51888103) of NSFC; the Fundamental Research Funds for the Central Universities and the National Key Research and Development Program of China (2021YFB4001405); Southeast University basic research program; General Program of NSFC; Jiangsu provincial basic research program supported this work.

###

Reference
Authors: YONG YU, M.A.K. YOUSAF SHAH, HAO WANG, XIAOMENG CHENG, LIEJIN GUO, JIANBING HUANG , PETER LUND , AND BIN ZHU
Title of original paper: Synergistic Proton and Oxygen Ion Transport in Fluorite Oxide-Ion Conductor
Journal: Energy Material Advances
DOI: 10.34133/energymatadv.0081
Affiliations: ¹State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University, Xi’an 710049, China. ²Jiangsu Provincial Key Laboratory of Solar Energy Science and Technology/Energy Storage Joint Research Center, School of Energy and Environment, Southeast University, Nanjing 210096, China. ³School of Science, Aalto University, FI-00076 Aalto(Espoo), Finland.
About Dr. Huang: Dr. Jianbing Huang (Corresponding author), Associate Professor, is affiliated with the State Key Laboratory of Multiphase Flow in Power Engineering, School of Energy and Power Engineering, Xi'an Jiaotong University. Member of Hydrogen Energy Committee of China Renewable Energy Society.