Catalytic Polyelectrolyte Multilayers at the Bipolar Membrane Interface

Abstract

Bipolar membranes are laminated anion and cation exchange membranes that split water at their interface very efficiently upon application of an electric field. This paper investigates the layer-by-layer (LbL) deposition of polyelectrolyte multilayers, as a tool to introduce molecularly thin catalyst groups at this interface of bipolar membranes. The bipolar membranes were prepared by first modifying an anion exchange membrane by consecutive dipping LbL assembly, then casting a thin highly charged intermediate layer followed by casting a cation exchange layer. The results reveal that polyelectrolytes of higher charge density coated on the anion exchange layer yield better performance. Several parameters of the LbL interface deposition were varied. Out of the investigated LbL assembly parameters, ionic strength and number of layers have shown the largest influence on catalytic activity as well as ionic selectivity. The membrane with two bilayers of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and poly(ethyleneimine) (PEI), where the PEI was prepared in 0.5 M NaCl, gave rise to the best performance. Surprisingly, detailed data analysis at low electrical potential suggests that the interface layers of a bipolar membrane play a major role in its permselectivity. Previously, only the bulk thickness of the anion and cation exchange membrane was assumed to influence the bipolar membrane selectivity.

Long term physical and chemical stability of polyelectrolyte multilayer membranes

“…This has led to a wide variety of possible applications of PEMs, including the modification of membranes to improve many aspects of their performance. Membranes have for instance been modified with PEMs to make membranes low fouling [5,6], responsive [7], but also to produce new nanofiltration [8][9][10][11], bipolar [12], ion selective [13], and solvent resistant membranes [14].…”

Modification of asymmetric bipolar membranes by functionalized hyperbranched polymers and their investigation during pH correction of diluted electrolytes solutions by electrodialysis

“…7b). The second limiting current caused by the diffusion limitations of water molecules delivery to bipolar junction [1,12] in the experiment for pH correction of the dilute solution was not achieved. and ОН -ions on the current density of bipolar membrane MB-3 with phosphoric acid groups is presented in Fig.…”

“…In the recent research [12] was presented the original layer-by-layer (LBL) technology of polyelectrolytes deposition on the bipolar membrane interface with a controllable thickness of bipolar junction. Authors produced the bipolar membranes, where the commercial anionexchange membrane Fumasep (produced by FuMA-Tech, Germany) was used as the anionexchange layer.…”

“…Moreover, despite the increase of effective contact area [13] and the increase of the quantity of bilayers from two to six does not lead to a decrease in the voltage drop across the bipolar membrane. The authors [12] showed that the reason of bipolar membrane efficiency reduction is due to increase in the bipolar junction thickness. An increase in the limiting current density found from I-V curves also was observed with increase in bilayers quantity.…”

Electrochemical nanoarchitectonics and layer-by-layer assembly: From basics to future

“…By using a different strategy, Wessling and coworkers assembled catalytic PEM in a bipolar membrane device (Fig. 7) [235]. When a PEDOT-PSS/PEI multilayer was deposited on a bipolar Figure 7 LbL modified bipolar electrodes for water splitting.…”