Studies on Anion Exchange Membrane and Interface Properties by Electrochemical Impedance Spectroscopy: The Role of pH
Wenjuan Zhang,
Wei Cheng,
Ramato Ashu Tufa,
Caihong Liu,
David Aili,
Debabrata Chanda,
Jing Chang,
Shaopo Wang,
Yufeng Zhang,
Jun Ma
Affiliations
Wenjuan Zhang
Tianjin Key Laboratory of Aquatic Science and Technology, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
Wei Cheng
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
Ramato Ashu Tufa
Department of Energy Conversion and Storage, Technical University of Denmark, Building 310, 2800 Kongens Lyngby, Denmark
Caihong Liu
Key Laboratory of Eco-Environments in Three Gorges Reservoir Region, College of Environment and Ecology, Chongqing University, Ministry of Education, Chongqing 400044, China
David Aili
Department of Energy Conversion and Storage, Technical University of Denmark, Building 310, 2800 Kongens Lyngby, Denmark
Debabrata Chanda
College of Chemistry and Chemical Engineering, Henan University, Kaifeng 475004, China
Jing Chang
Tianjin Key Laboratory of Aquatic Science and Technology, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
Shaopo Wang
Tianjin Key Laboratory of Aquatic Science and Technology, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
Yufeng Zhang
Tianjin Key Laboratory of Aquatic Science and Technology, School of Environmental and Municipal Engineering, Tianjin Chengjian University, Tianjin 300384, China
Jun Ma
State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, Harbin 150090, China
Ion-exchange membranes (IEMs) represent a key component in various electrochemical energy conversion and storage systems. In this study, electrochemical impedance spectroscopy (EIS) was used to investigate the effects of structural changes of anion exchange membranes (AEMs) on the bulk membrane and interface properties as a function of solution pH. The variations in the physico/electrochemical properties, including ion exchange capacity, swelling degree, fixed charge density, zeta potentials as well as membrane and interface resistances of two commercial AEMs and cation exchange membranes (CEMs, as a control) were systematically investigated in different pH environments. Structural changes of the membrane surface were analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. Most notably, at high pH (pH > 10), the membrane (Rm) and the diffusion boundary layer resistances (Rdbl) increased for the two AEMs, whereas the electrical double layer resistance decreased simultaneously. This increase in Rm and Rdbl was mainly attributed to the deprotonation of the tertiary amino groups (-NR2H+) as a membrane functionality. Our results show that the local pH at the membrane-solution interface plays a crucial role on membrane electrochemical properties in IEM transport processes, particularly for AEMs.
