ed Frontier Sciences,Kyushu University r nerqy Week 2022 Study of nanocellulose crosslinking with organic acids for improved proton conductivity in bio-based proton exchange membranes Selyanchyn Olena D3, Department of Automotive Sciences, Graduate School of Integrated Frontier Sciences, Kyushu University core technological element of the  sustainable “Hydrogen society” Barriers for wide deployment of fuel cells: > Cost of hydrogen ack of infrastructure (e.g. fuelling stations) > Cost of fuel cells (Pt in electrocatalyst, bipolar Benchmark materials for PEM – perfluorinated sulfonic acid ionomers: Nafion®, Aquivion®, 3M® Disadvantages: high-cost, non-recyclable Purpose of this work: Development of low-cost and efficient PEM based on nanocellulose Nanocellulose can be obtained from variety of biomass sources: – acid hydrolysis (nanocrystals) – mechanical shearing (nanofibers) – microorganisms (bacterial nanocellulose) Characteristic properties: – high mechanical strength – low density and high surface area – non toxicity and biodegradability – flexibility Plant cell wall mechanical, chemical tretment Higher plants, bacteria, simple animals (e.g. tunicates) Molecular structure (a) Pristine cellulose without modification (b) Partially sulfonated cellulose Good mechanical  stability Stability in boiling water Improved chemical stability Controlled ion-exchange capacity Appropriate proton conductivity (c) Sulfonated cellulose crosslinked with organic sulfonic acid The study aims to clarify what is more important for the proton conduction: “backbone sulfonation” or “sulfonation via added crosslinker”. Therefore investagation of these factors on proton conduc- tivity and mechanical properties is planned. Materials will be designed with a various content of two types of sulfonation. se nanocrystal-based membranes: influence of crosslinking amount: the mebranes visual change but chemically similar to CNC (XPS, FTIR) and crosslinker can be chemicaly accomodated.
PROTON CONDUCTIVITY IN CNC WITH BACKBONE SULFONATION
Proton conductivity measured by impedance spectroscopy (through-plane mode at varied temperatures and relative humidity) – The technological process for CNC fabrication (acid hydrolysis) results in a different values of sulfonation – Understanding/utilization of backbone sulfonation can have significant impact on final conductivity – The differences of the proton conductivity can be higher than 20 times (desulfated vs. CNC Univ. of Maine)
PROTON CONDUCTIVITY IN CROSSLINKED CNC
Crosslinked CNC
CONCLUSIONS
– CNC  is a promising biopolymer platform for developing novel PEM via the sulfonic acid crosslinking pathway – The structural integrity of the sulfosuccininc acid crosslinked CNC membranes with up to 35% of the acid in membrane forming mixture – Chemical structure confirmed via XPS and FTIR, IEC measurements shows that acid is bound via esterification route, stable even at higher temperatures (>100 C) – More than 100 times increase in conductivity of crosslinked membranes compared to source CNC (Celluforce, Inc. Canada) Results of this work compared to literature shows that utilization of acid crosslinking of crystalline nanocellu- lose allows substantial increase in the proton conduc- tivity (2 orders of magnitude) while backbone sulfon- ation has a smaller impact. – Considering high gas barrier of nanocellulose membranes PEMs with competitive properies (specific resistance and mechanical stability) can be fabricated – CNC membranes present an environmentally friendly and substantially lower cost option compared to industrial benchmarks (e.g. Nafion). – Essentially , these “paper” based PEMs can find their niche application in portable low cost applications (e.g. unmanned aerial or underwater vehicles) Kyushu University Platform of Inter/Transdisciplinary Energy Research Support Program for Doctoral Students JST SPRING (Grant Number JPMJSP2136) E-mail: olenoselvenchyn@ignol.com  /   Corresponding author: Prof. S.M. Lyth lyth@i2cneckyashu-u.oc.jp  / The Lyth Lab: htps://siles.google.com/view/lyhiab/ – uniform thickness in casted membranes (aqueous solution) – natural drying (no extra energy) – suitable for mass production – flat and stable after hot-pressing
Membranes features:
“Eco-friendly, low-cost material platform for advanced materials Superior mechanical  stability Ultra-low proton conductivity Deteoriation in humid environment Low mechanical  stability Improved proton conductivity Solubility in water