ACS Spotlight: Bipolar Membranes for Electrochemical Energy Conversion, Chemical Manufacturing, and Separations

Abstract

Sustainable energy conversion, chemical manufacturing, and separations are central to addressing the world's energy and environmental challenges. Electrochemical platforms stand as a cornerstone in addressing these challenges because they are low exergy and can be powered on renewable electrons. In electrochemical systems, bipolar membranes (BPMs) are emerging as a unique class of ion exchange membranes poised to revolutionize various electrochemical processes via pH control of anode and cathode chambers and in situ pH adjustment. In this Spotlight Review, we provide a comprehensive review of electrochemical platforms utilizing BPMs for energy conversion (water electrolyzers for hydrogen production, fuel cells, and flow batteries), chemical manufacturing (electrolyzers that convert carbon dioxide into value-added chemicals and nitrate into ammonia), and separations. The motivation for using BPMs, as well as their performance and durability, in electrochemical platforms are disseminated. We also discuss current challenges that impede BPM electrochemical systems from competing with state-of-the-art electrochemical systems using monopolar ion-exchange membranes (e.g., anion/hydroxide exchange membranes and cation/proton exchange membranes). The review also covers molecular modeling and continuum modeling efforts to understand the basic mechanisms that govern BPM performance.

Effects of Ionic Interferents on Electrocatalytic Nitrate Reduction: Mechanistic Insight

“…A dual-chamber cell (DCC) exhibits a more severe pH variation in two compartments compared to a single-chamber cell (SCC), which may lead to Ca 2+ precipitation in the form of Ca­(OH) 2 or CaCO 3 . , For future applications, a continuous flow reactor with long-term electrode/electrolyte stability and high current density is preferred . The use of a bipolar membrane (BPM) is a promising method to modulate proton supply and pH variation and avoid unintended ionic crossovers. , Furthermore, in a single-cell reactor, the impact of the electrolyte concentrating throughout the process requires meticulous attention.…”