Submitted:
17 September 2026
Posted:
18 September 2026
You are already at the latest version
Abstract
Chitosan is an appealing matrix for low-cost separator membranes in water electrolysis, but fillers are normally screened one at a time and judged on mechanical grounds, so the way a filler simultaneously reshapes hydration and ionic transport is rarely mapped across a single consistent series. We cast seven membranes from chitosan extracted in-house from Litopenaeus vannamei shells — pristine chitosan and composites containing graphite (1 wt.%), bamboo cellulose nanocrystals (1 and 3 wt.%), graphene oxide (1 and 3 wt.%) and a ternary 1 wt.% NCC/1 wt.% GO formulation — and characterised all of them by proximate analysis, DSC, electrolyte uptake in 1 wt.% KOH, uniaxial tension, Shore D hardness, a five-cycle ultrasonic ageing protocol and polarisation in a purpose-built two-compartment cell. The two filler families moved hydration and transport in opposite directions. Nanocellulose raised the moisture content from 11.00% to 13.46% while lowering the conductivity of the casting dispersion by 12.5% and 23.2% at 1 and 3 wt.%; graphene oxide cut moisture to 6.42% and raised dispersion conductivity by 18.4% and 25.9%. Across the series the two quantities were inversely correlated (r = −0.761, p = 0.047). Electrolysis onset potential tracked dispersion conductivity (Spearman ρ = −0.857, p = 0.014) but showed no relationship with tensile strength (p = 0.125), so the functional gain from a filler is not predictable from the mechanical data alone. Loadings above 1 wt.% degraded every property measured, and the 3 wt.% GO membrane was the only composite to fail the ageing protocol. Filler selection for these membranes is therefore a compromise, not an optimisation.
Keywords:
chitosan
; cellulose nanocrystals
; graphene oxide
; biocomposite membranes
; water electrolysis
; electrolyte uptake
; proximate analysis
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