Entanglement-Enhanced Water Dissociation in Bipolar Membranes with 3D Electrospun Junction and Polymeric Catalyst

Abstract

With the use of bipolar membranes (BPMs) in an expanding range of applications, there is an urgent need to understand and improve the catalytic performance of BPMs for water dissociation, as well as to increase their physical and chemical stability. In this regard, electrospinning BPMs with 2D and 3D junction structures have been suggested as a promising route to produce high-performance BPMs. In this work, we investigate the effect of entangling anion and cation exchange nanofibers at the junction of bipolar membranes on the water dissociation rate. In particular, we compare the performance of different tailor-made BPMs with a laminated 2D junction and a 3D electrospun entangled junction, while using the same type of anion and cation exchange polymers in a single/dual continuous electrospinning manufacturing method. The bipolar membrane with a 3D entangled junction shows an enhanced water dissociation rate as compared to the bipolar membrane with laminated 2D junction, as measured by the decreased bipolar membrane potential. Moreover, we investigate the use of a third polymer, that is, poly­(4-vinylpyrrolidine) (P4VP), as a catalyst for water dissociation. This polymer confirmed that a 3D entangled junction BPM (with incorporated P4VP) gives a higher water dissociation rate than does a 2D laminated junction BPM with P4VP as the water dissociation catalyst. This work demonstrates that the entanglement of the anion exchange polymer with P4VP as the water dissociation catalyst in a 3D junction is promising to develop bipolar membranes with enhanced performance as compared to the conventionally laminated membranes.

Continuous ammonia electrosynthesis using physically interlocked bipolar membrane at 1000 mA cm−2

“…Such elaborate array architecture could form AEL-CEL interlocking layer with densely dispersed micropores. By overcoming the drawbacks in previous studies for 3D interlayers (electrospinning or photoetching template) 33,34 , this approach realized MBM with highly ordered interlayer structure at sub-micro scale and conceivably offers MBM with not only abundant WD catalytic sites but also a strong combination of both layers for relieving blistering or delamination of AEL and CEL in practical applications.…”

“…− can be easily transferred through the 3D framework to Co nanoarray possessing abundant catalytic sites, which can also be proved by the depth of microporous and the bulky surface area (Supplementary Figs. 33 48 , the MBM electrosynthesis system is prospective to work with ~90% efficiency at ampere-level currents.…”

“…In reality, working at high current density will bring BMs with exponential challenging, mainly expressing in two aspects: (i) insufficient catalytic sites for WD reaction at the interface of anion exchange layer (AEL) and cation exchange layer (CEL); (ii) ballooning of AEL and CEL interface 27 . Conventional wisdom has provided rational designs for interfacial catalysts [28][29][30][31] or structure [32][33][34] for optimization of BMs under the discipline of protonation-deprotonation mechanism; nevertheless, while most efforts hardly take effect averting the predicament of both points simultaneously, especially for high current density. Incremental catalysts promote WD kinetics but enlarge the physical space between AEL and CEL, thus inevitably increase ionic transportation resistance and the possibility of interfacial blistering.…”

Potential of Dipicolinic Acid as a Water-Dissociating Catalyst in a Bipolar Membrane

“…Under reverse bias, water dissociation phenomena in BPM could be achieved even without the use of interface catalysts by optimizing the thickness and functionalization degree of each membrane layer (CEL/AEL). , Chabi et al reported the synthesis of transparent BPM from highly functionalized CEL (Nafion, NR-211 of thickness 25 ± 3 μm) and AEL (poly­(benzimidazolium), PBI of thickness 55 ± 3 μm) without the use of any interface catalysts, and the water dissociation onset potential, U diss (also denoted as V diss or E onset in the literature), was ∼0.87 V. Another homogeneous BPM of Abdu et al, made by laminating commercial anion exchange membrane (AEM, FAA of thickness 140 ± 10 μm) and cation exchange membrane (CEM, FKB of thickness 90 ± 10 μm) without any interface layer showed U diss ∼ 1.1 V, and it was reduced further by the incorporation of multilayered polyelectrolyte (poly­(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/polyethylenimine (PEI)) as the interface catalyst. McDonald and Freund reported U diss = 0.9 V with homogeneous BPM prepared by laminating commercial AEM (AHA of thickness 180 ± 5 μm) and CEM (Nafion NR-211 of thickness 20 ± 5 μm) without any interface, which could be further reduced to 0.8 V through the incorporation of graphene oxide (GO) nanoparticles as the interface catalyst.…”

Nanocomposite interface coupled with thickness optimization promoting water dissociation in heterogeneous bipolar membrane

“…The dissociation of water molecules is understood to be the combined effect of: (i) protonation and deprotonation of water molecules through the fixed charge groups of CEL/AEL, and (ii) second Wien effect (i.e., dissociation of weak electrolyte under applied potential) 8 . The second Wien effect is found to be dominant in BPM with no interface, 9,10 where physiochemical/electrochemical properties and available charge groups (charge density) of CEL/AEL promote water dissociation 11,12 . Liu et al 13 reported drop in onset water dissociation potential (U diss ) with the extent of functionalization, that is, higher charge density.…”