Disentangling water, ion and polymer dynamics in an anion exchange membrane

Abstract

The use of fuel cell (FC) devices for power generation is developing rapidly as we transition from fossil--fuelled combustion to electrochemical propulsion and stationary power systems. PEMFCs operate by electrochemically splitting molecules such as H2/CH3OH to produce H + or OH -ions at the anode along with electrons that are directed through an external circuit to generate electrical power. The ions are transported via an ionically conducting polymer (ionomer) to participate in recombination reactions at the opposite electrode [1]. Cell performance is determined by the electrocatalytic efficiency of supported transition metal nanoparticles at the electrodes and by the transport dynamics of ions and water within the electrolyte. A large class of H + --conducting ionomers is derived from the Nafion family of sulfonated tetrafluoroethylene--based fluoropolymer--copolymers, while OH ----conducting membranes are commercially available as the Fumasep

Fast Hydroxide Conduction via Hydrogen-Bonding Network Confined in Benzimidazolium-Functionalized Covalent Organic Frameworks

“…Interestingly, checking the configuration of water molecules close to the COFs, the oxygen atoms tend to face the skeleton, while the hydrogen atoms prefer to point inward to form hydrogen bonds with other water molecules. Collectively, these results may provide support for further explanation of the transport of OH – via proton-exchange hopping other than vehicle-like OH – anion migration. , …”

“…Collectively, these results may provide support for further explanation of the transport of OH − via proton-exchange hopping other than vehicle-like OH − anion migration. 31,32 An AEM was fabricated by dispersing Tp-PMBIm-OH-COF into poly(2-bromomethyl-6-methyl-1,4-phenylene oxide) matrices (Supporting Information) (Figure S26). A modest water uptake of the AEM membrane is required for ion transport; the ion availability would be restricted if the water uptake is too low, while an excessive water uptake would reduce the dimensional stability of the AEM.…”

Uncovering the Dynamics of Confined Water Using Neutron Scattering: Perspectives

“…implying a single Fouriertime window, are usually incomplete. This implies that even if current QENS methods allow for a range of observation time covering four orders of magnitude (10 −9 -10 -13 s), a combination of several different spectrometers is normally required to obtain a full understanding of the relevant dynamics [17,32,33]. However, the extraordinary flexibility of the time-of-flight backscattering spectrometer MIRACLES [19,28] being built at ESS will bring a paradigm shift to QENS studies.…”

Ultrathin anion exchange membranes with an improved OH− transfer rate for high-performance AEMFCs

“…Alkaline anion exchange membrane fuel cells (AEMFCs) that produce electricity directly from H 2 and O 2 are a promising technology in the future mainstream energy eld due to their prominent cost advantage, [1][2][3] wherein alkaline anion exchange membranes (AEMs) are deemed to be the core component that inuences the performance and durability of AEMFCs. [4][5][6] Aer years of efforts, the conductivity and stability of current AEMs have been greatly improved. So, the conductivity of AEMs is no longer the main obstacle to restricting the application and the performance improvement of AEMFCs.…”