No abstract

Bipolar membranes (BPMs) are increasingly being applied in chemical recovery and energy storage fields due to their unique water dissociation ability under reverse bias. BPMs capable of dissociating water at a lower potential will minimize energy consumption, and it depends on the thickness asymmetry between the cation exchange layer (CEL)/anion exchange layer (AEL) and the right catalyst material used at the interface of CEL/AEL. In this report, a heteroaromatic compound, 2,6-pyridine-dicarboxylic acid (also known as dipicolinic acid, DPA), is being proposed to be an effective interface catalyst for BPM made of sulfonated poly(ether ether ketone) (CEL) and quaternized polysulfone (AEL). The optimum concentration of DPA as an interface layer over fabricreinforced AEL was found using an adsorption study. The thickness asymmetry between CEL and AEL (without catalyst) alone could lower the water dissociation onset potential (U diss ) to 0.72 V, which was further reduced to 0.70 V using DPA as an interface catalyst. After 5 h of electrodialysis experiments at 25 mA• cm −2 , the acid (or base) concentration increased from ∼0.19 mol•L −1 (without catalyst) to 0.21 mol•L −1 due to the presence of DPA at the interface. Meanwhile, operational studies performed using synthetic reverse osmosis (RO) reject of sea water confirm the consistency in the acid−base production during multiple cycles.

Bipolar membranes (BPMs) are multilayered composite film containing an interface layer sandwiched between cation exchange layer (CEL) and anion exchange layer (AEL), and are capable of dissociating water molecules under reverse bias potential. Woven fabric supported heterogeneous bipolar membranes (HBMs) were synthesized adopting layer‐by‐layer solvent casting technique. Nanocomposite layer based on sulfonated polyether ether ketone (SPEEK) and GO (graphene oxide) were applied at the interface of CEL/AEL made of cation/anion exchange resins and poly (vinyl chloride) as binder to advance water dissociation in HBMs. Thickness of monopolar layers were initially optimized without any interfacial layer. Introduction of SPEEK interface substantially lowered onset water dissociation potential, Udiss (~1.87 V) relative to the HBM without interface (~3.27 V), which got further reduced (~1.80 V) by nanocomposite (GO + SPEEK) interface. Udiss recorded with SPEEK + GO as interface was much lower than some of the recently reported homogeneous BPM. The NaOH production from NaCl (1.0 mol⋅L−1) solution in a bipolar membrane electrodialysis set up containing synthesized HBM with nanocomposite interface (SPEEK + GO) was double than that of NaOH concentration obtained with HBM having no interface, where the current density was fixed at 50.0 mA·cm−2. Careful optimization of monopolar/interface layer thickness and composition of nanocomposite interface results in developing cost effective HBMs facilitating water dissociation at lower potential.

No abstract

No abstract