Postgraduate research opportunities Nanocellulose as a sustainable electrolyte for electrochemical energy conversion

The Hydrogen Economy will help to shift society away from fossil fuels and contribute to decarbonisation. Polymer electrolyte membrane water electrolysis (PEMWE) can convert renewable energy into green hydrogen, whilst polymer electrolyte membrane fuel cells (PEMFCs) convert hydrogen into electrical power. Electrolyte membranes play multiple important roles in PEMWE and PEFCs.

They separate the electrodes preventing short circuits, and thus must be electronically insulating. They prevent the crossover of hydrogen and oxygen molecules between electrodes, and so must have low gas permeability. They convey hydrogen ions between the electrodes to take part in the REDOX reactions, and so must have high proton conductivity. Finally, they act as a support for the electrocatalyst, and so must be mechanically strong.

Few materials can meet these requirements simultaneously, and state-of-the- art PEMWEs and PEMFCs employ sulfonated fluoropolymers such as Nafion®. These have a hydrophobic polytetrafluoroethylene (PTFE) backbone with hydrophilic sidechains terminated by superacidic sulphonate groups. This class of ionomer has remained largely unrivalled as ionomer membranes since the 1960s.

Moving forward it is important to ensure that electrochemical processes do not rely on inherently unsustainable technologies or materials. However, the fluoropolymers used as electrolytes today are facing increased scrutiny due to their association with per- and polyfluoroalkyl substances (PFAS). These are a class of “forever chemicals” which persist in the environment causing ecological damage and health issues. Fortunately, there may still be time to replace these problematic materials.

Cellulose is a biopolymer found in the cell walls of plants and trees. It is the most abundant biopolymer on Earth, the primary constituent of wood, paper, and cotton. It is an inherently sustainable material. Cellulose fibres can be processed and broken down into cellulose nanofibers or even smaller cellulose nanocrystals, collectively known as nanocellulose.

Nanocellulose is a promising sustainable nanomaterial for applications in polymer reinforcement, food thickeners, adsorbents, cosmetics, and the pharmaceutical industry. Our research group showed that nanocellulose membranes are electronically insulating, have excellent gas barrier properties, can conduct protons, and are mechanically strong.

Postgraduate Certificate in Researcher Development (PGCert)

In addition to undertaking cutting edge research, students are also registered for the Postgraduate Certificate in Researcher Development, which is a supplementary qualification that develops a student’s skills, networks and career prospects.

We then confirmed that they can be used as sustainable electrolytes in PEFCs. In this project, your responsibility will be to make further advances in this exciting field. You will investigate the materials properties of different types of nanocellulose using a variety of advanced characterisation techniques. These will include impedance spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. You will investigate the chemical modification of nanocellulose with acidic functional groups and investigate the effect on proton conductivity.

You will investigate crosslinking to improve the mechanical strength and durability. Meanwhile, you will investigate the effect of blending nanocellulose with other electrolytic materials. Finally, you will incorporate your modified nanocellulose membranes into PEFC and PEMWE cells, comparing the performance with cells fabricated from conventional materials, and evaluating the durability.

Further information

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