High Temperature Proton Conduction in Nanocellulose Membranes: Paper Fuel Cells

Abstract

Polymer electrolyte membrane fuel cells (PEFCs) are an efficient and clean alternative power source, but the high cost impedes widespread commercialization. The fuel cell membrane, e.g. Nafion, contributes significantly to this cost, and therefore novel alternatives are required. Temperature is also an important factor; high temperature operation leads to faster reaction kinetics, lower electrocatalyst loading, and improved water management, thereby further reducing cost. However, higher temperature puts greater demands on the membrane. Conductivity is related strongly to humidification and therefore this generally decreases above 100°C. Nanocellulose membranes for fuel cells, in which the proton conductivity increases up to 120°C, are here reported for the first time. The hydrogen barrier properties are far superior to conventional ionomer membranes. Fuel cells with nanocellulose membranes are successfully operated at 80°C. Additionally, these membranes are environmentally friendly and biodegradable.

Imidazole-doped nanocrystalline cellulose solid proton conductor: synthesis, thermal properties, and conductivity

“…Thus, nanocrystalline cellulose doped with imidazole is a promising material for a possible application as a membrane in fuel cells in which the proton conductivity increases up to 140°C. Earlier, increases in proton conductivity in nanocellulose membranes up to 120°C have been reported under strong humidification (Bayer et al 2016).…”

“…In all cases, the estimated error is ± 0.01 eV. The activation energies for proton conduction in the studied NCC and NCC-Im films are higher than those of cellulose nanofibers and nanocrystals (E a = 0.21 and 0.24 eV, respectively) (Bayer et al 2016), and Nafion (E a = 0.16 eV) (Kreuer et al 1993). The latter values of activation energies are characteristic of Grotthuss mechanism (Agmon et al 1995) which dominates at high humidity.…”

“…Such a rapid development of nanocellulose in a variety of fields is related to its unique properties including also its ability to form films and gels. The first report on pure nanocellulose membranes for fuel cells in which the proton conductivity was observed above 100°C was published by Bayer (Bayer et al 2016). They studied the proton conductivity of pure cellulose nanocrystals and pure cellulose nanofibers over a wide temperature range and humidity.…”

Nanocellulose as a green and sustainable emerging material in energy applications: a review

“…With the dense packing of NCC in the form of a solid film and its minimal porosity, compared to traditional paper treated with conductive material, the obtained NCC nanopaper film demonstrated improved conductivity. Meanwhile, nanocellulose can bound cellulose fibers, can form strong/tough networks, and is used as a strength enhancement additive in paper industries . Such nanopaper is an excellent candidate for developing flexible electronics with the benefits of being lightweight and good thermal/chemical stability.…”

“…Progress on the preparation of flexible electronics and transparent NCC nanopaper has been reported recently, whereby a mixture of nanopaper and conductive materials enables the formation of conductive nanopaper composites. NCC nanopaper also has been reported in composite electronics with tin oxide layers for flexible organic field effect transistor …”