Functionalized biopolymer based bipolar membrane with poly ethylene glycol interfacial layer for improved water splitting

This study investigates the effect of poly ethylene glycol (PEG) of different molecular weight (MW) as interfacial layer (IL) of bipolar membrane (BPM) for water dissociation. Chitosan (CS) was modified to N-methylene phosphonic chitosan (PC) and quaternized chitosan (QC), for preparing cation- and anion-exchange layer (CEL and AEL, respectively) of BPM. Different BPMs were prepared by layer-by-layer solution casting method (in aqueous media to achieve the good adhesion between layers) using PEG of different MWs (200–3400 Da) as IL. CEL and AEL with good ion-exchange properties were separately evaluated for their physicochemical and electrochemical characterizations. All BPMs with IL (PEG) were evaluated from current–voltage (I–V) curves and water dissociation efficiency. The experimental results proved the excellent catalytic activity of PEG for water dissociation, which further improved with its MW. Furthermore, electrodialysis with bipolar membrane (EDBPM) experiments confirmed the occurrence of water dissociation at BPM interface and thus formation of acid and base.

Research highlights
► Chitosan was modified to N-methylene phosphonic chitosan (PC) and quaternized chitosan (QC), for the preparation bipolar membrane (BPM).
► Different BPMs were prepared by layer-by-layer solution casting method (in aqueous media to achieve good adhesion between CEL and AEL l) with using different MWs (200–3400 Da) PEG as interfacial layer (IL).
► All BPMs with PEG at IL are evaluated by current–voltage (I–V) curves and water dissociation efficiency.
► The experimental results proved that PEG has excellent water dissociation efficiency.