High-Performance Bipolar Membrane Development for Improved Water Dissociation.

Abstract

Bipolar membranes (BPMs) are the enabling component of many promising electrochemical devices used for separation and energy conversion. Here, we describe the development of high-performance BPMs, including two-dimensional BPMs (2D BPMs) prepared by hot-pressing two preformed membranes and three-dimensional BPMs (3D BPMs) prepared by electrospinning ionomer solutions and polyethylene oxide. Graphene oxide (GOx) was introduced into the BPM junction as a water-dissociation catalyst. We assessed electrochemical performance of the prepared BPMs by voltage-current (V-I) curves and galvanostatic electrochemical impedance spectroscopy. We found the optimal GOx loading in 2D BPMs to be 100 μg cm-2, which led to complete coverage of GOx at the interface. The integration of GOx beyond this loading moderately improved electrochemical performance but significantly compromised mechanical strength. GOx-catalyzed 2D BPMs showed comparable performance with a commercially available Fumasep BPM at current densities up to 500 mA cm-2. The 3D BPMs exhibited even better performance: lower resistance and higher efficiency for water dissociation and substantially higher stability under repeated cycling up to high current densities. The improved electrochemical performance and mechanical stability of the 3D BPMs make them suitable for incorporation into CO2 electrolysis devices where high current densities are necessary.