Tuning the Interfacial Electrical Field of Bipolar Membranes with Temperature and Electrolyte Concentration for Enhanced Water Dissociation

Creators: Zhang, Huanlei; Cheng, Dongbo; Xiang, Chengxiang¹; Lin, Meng

1. California Institute of Technology

Abstract

A coupled experimental and numerical study was performed for a fundamental understanding of the impact of operating conditions, i.e., temperature and electrolyte concentration, as well as interfacial abruptness, on the bipolar membrane (BPM) performance. A comprehensive multiphysics-based model was developed to optimize the operation condition and interfacial properties of BPM, and the model was used to guide the design and engineering of high-performing BPMs. The origin of the enhanced BPM performance at a high temperature was identified, which was attributed to the intrinsic reaction rate enhancement as well as the increase in electrolyte ionic conductivity. The experimentally demonstrated current density–voltage characteristics of BPMs clearly exhibited three distinctive regions of operation: ion-crossover region, water dissociation region, and water-limiting region, which agreed well with the multiphysics simulation results. In addition, the model revealed that a sharper interfacial abruptness led to improved BPM performance due to the enhanced interfacial electric field at the water dissociation region. The decrease of the electrolyte concentration, which increased the dielectric constant of the electrolyte, enhanced the interfacial electric field, leading to improved electrochemical performances. The present study offers an in-depth perspective to understand the species transport as well as water dissociation mechanism under various operation conditions and membrane designs, providing the optimal operation conditions and membrane designs for maximizing the BPM performance at high current densities.

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Acknowledgement

The authors acknowledge the funding support from the National Natural Science Foundation of China under Grant No. 52006097, the Shenzhen Science and Technology Innovation Commission under Grant No. GJHZ20210705141808026, Guangdong Basic and Applied Basic Research Foundation under Grant No. 2023A1515011595, and Gangdong grant under Grant No. 2021QN02L562. The computation in this work is supported by the Center for Computational Science and Engineering at the Southern University of Science and Technology. The bipolar membrane multiphysics model is based on the work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266.

Data Availability

Details of the experimental methods; transport parameters used for water; fixed charge and catalyst distribution; mesh and tolerance independent studies; stability test data over 10 h; the contribution of catalyzed pathway and uncatalyzed pathway (PDF)

Conflict of Interest

The authors declare no competing financial interest.

Contributions

H.Z. and D.C. contributed equally to this work.

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