(131k) Achieving High Performance Bipolar Membranes Via Hydrocarbon Polymers and Facile Catalyst Loading

Bipolar membranes (BPMs) have garnered significant attention for their ability to dissociate water into H⁺ and OH⁻ ions at the junction of their cation- and anion-exchange layers in the presence of an externally applied electric field. This key feature enables BPMs to serve as a core component in diverse applications, including water electrolysis, electrochemical acid–base generation, CO₂ capture and conversion, and energy storage systems. Despite this broad potential, existing BPM technologies face critical material limitations that hinder their practical deployment. Commercial BPMs exhibit inadequate stability, particularly at high current densities, and are costly. Most research BPMs rely on Nafion as the cation-exchange layer due to its high conductivity and chemical stability. However, Nafion is a fluorinated polymer, raising substantial concerns over environmental persistence and toxicity, and its synthesis involves complex, resource-intensive processes that drive up cost. These limitations highlight the need for more sustainable, cost-effective alternatives.

To address this challenge, we developed hydrocarbon-based BPMs using inexpensive and commercially available pentablock copolymer membranes. This material platform not only eliminates fluorine from the structure—thereby reducing environmental impact—but also enables a more straightforward and scalable membrane fabrication process. Furthermore, we developed a catalyst-loading strategy that facilitates uniform deposition of water dissociation catalysts at the junction. This approach bypasses the need for elaborate interfacial engineering techniques that often lack scalability. The resulting BPMs exhibited enhanced water dissociation kinetics relative to benchmarks, including BPMs made from the same hydrocarbon-based membranes but with conventional catalyst deposition strategies (i.e., spray or spin coating). These findings establish a promising platform for the development of fluorine-free and high-performance BPMs, particularly suited for next-generation electrochemical processes.