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

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.

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

“…5c and Supplementary Figs. [29][30][31][32]. To conquer the severe HER at high current, the principle of design is to enhance mass transfer by a multilevel structure, thus reactant NO 3…”

“…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.…”

“…Co 3D nanoarray (Supplementary Figs. [29][30][31][32][33][34][35] and the as-prepared NiFe foam 48 were adopted to be cathodic and anodic catalysts. The effective working area for both anode and cathode electrodes is 3.0 cm 2 , respectively, sandwiching a bipolar membrane slightly larger to avoid electrolytes convection on both sides.…”

Recent Development and Challenges of Bipolar Membranes for High Performance Water Electrolysis

“…In addition to the polymer materials and structures of CEM and AEM, it is shown that the thickness of each AEL or CEL layers also strongly affect the overall BPM performance. ,,,, There have been intensive studies to optimize the membrane thickness of BPMs. In this section, we will elaborate some recent progress and accomplishments on this aspect.…”

“…The addition of a WD catalyst to the interfacial junction can drastically enhance the performance of BPM with fast WD kinetics at high current densities. ,,,, However, the underlying WD mechanisms at BPM junctions remain unclear, specifically regarding the electric field in the junction for WD catalysts with different electronic and dielectric properties along with varying thicknesses. Shannon et al recently proposed a microscopic model to describe the electrocatalytic processes at the BPM interface where WD is imbedded at the IL (Figure a). , The transport of H + and OH – in water follows the Grotthuss mechanism, which involves the transfer of charge through a series of protonation and deprotonation steps on different water molecules.…”