Enhanced mechanical strength and sustainable biomass-derived bipolar membranes with in-situ embedded LDH nanosheets for efficient water splitting

Bipolar membranes (BPMs) enable efficient water dissociation into protons and hydroxide ions for sustainable energy conversion and resource recovery, yet conventional BPMs face challenges including high overpotential, environmental drawbacks of synthetic polymers, and the conductivity-stability trade-off. Herein, we develop a robust and eco-friendly BPM by in-situ embedding layered double hydroxide (LDH) nanosheets into a fully biomass-derived matrix of polyvinyl alcohol (PVA) and quaternized chitosan (QCS). The optimized membrane (BM-QPL-4) achieves a low transmembrane voltage of 0.746 V at 100 mA·cm −2 and maintains 0.713 V over 72 h at 50 mA·cm −2 , coupled with 40% enhancement in mechanical strength (33.31 MPa) and reduced swelling ratio (61.52%). These improvements arise from the uniformly dispersed LDH, which strengthens the polymer matrix while serving as built-in catalysts and ion-conductive pathways. The synergistic surface hydroxyl catalysis and interfacial electric field—described by “pore-field coupling” model—collectively lower the water dissociation energy barrier from 0.97 eV to 0.56 eV. The work demonstrates a sustainable and mechanically robust BPM platform with great potential in advanced water electrolysis and resource recovery, providing a scalable and generalizable strategy for incorporating functional nanomaterials into polymer matrices.