Exceptionally high proton conductivity in Eu2O3 by proton-coupled electron transfer mechanism

Shuo Wan; M A K Yousaf Shah; Hao Wang; Peter D Lund; Bin Zhu

doi:10.1016/j.isci.2023.108612

Exceptionally high proton conductivity in Eu₂O₃ by proton-coupled electron transfer mechanism

iScience. 2023 Nov 30;27(1):108612. doi: 10.1016/j.isci.2023.108612. eCollection 2024 Jan 19.

Authors

Shuo Wan¹, M A K Yousaf Shah¹, Hao Wang¹, Peter D Lund^{1

2}, Bin Zhu¹

Affiliations

¹ Jiangsu Provincial Key Laboratory of Solar Energy Science and Technology/ Energy Storage Joint Research Center, School of Energy & Environment, Southeast University, Nanjing 210096, China.
² School of Science, Aalto University, P.O. Box 15100, 00076 Aalto, Espoo, Finland.

Abstract

Proton conductors are typically developed by doping to introduce structural defects such as oxygen vacancies to facilitate ionic transport through structural bulk conduction mechanism. In this study, we present a novel electrochemical proton injection method via an in situ fuel cell process, demonstrating proton conduction in europium oxide (Eu₂O₃) through a surficial conduction mechanism for the first time. By tuning Eu₂O₃ into a protonated form, H-Eu₂O₃, we achieved an exceptionally high proton conductivity of 0.16 S cm^-1. Distribution of relaxation time (DRT) analysis was employed to investigate the proton transport behavior and reveal the significant contribution of surface proton transport to the overall conductivity of Eu₂O₃. Remarkably, H-Eu₂O₃ exhibited a low activation energy for ionic transport, comparable to the best ceramic electrolytes available. The proton-coupled electron transfer (PCET) mechanism describes this novel surficial proton conduction mechanism. These findings provide new possibilities for developing advanced proton conductors with improved performance.

Keywords: Electrochemical energy conversion; Energy application; Materials science.