Bio-engineered gas diffusion electrodes (GDEs) for proton exchange membrane fuel cells (PEMFCs)

Abstract

The current cost and finite nature of Platinum Group Metals (PGM) is a barrier to the successful commercialisation of Proton Exchange Membrane Fuel Cells (PEMFCs). Successful mass production of fuel cell components combined with the recovery of PGMs from waste, more efficient PGM use or the replacement of PGMs catalyst is necessary to reduce costs per unit. Current hydrometallurgy and pyrometallurgy techniques do not provide a ‘clean’ or economically viable solution to PGM recovery when compared to bio-hydrometallurgy. Bio-catalysts can be manufactured by coupling the oxidation of hydrogen to the reduction of soluble metallic species [e.g. Pd(II), Pt(IV)] via Hydrogenase enzymes. The work presented in this thesis aims to evaluate the incorporation of biohydrometallurgy in producing Gas Diffusion Electrodes (GDEs) for PEM Fuel cell applications. The biomineralisation and subsequent catalytic activity of spin coated engineered biofilms is investigated, as is the use of planktonic cell generated bio-catalysts in traditional GDE fabrication via screen printing. Although biofilms were found to produce layers containing active PGM particles, the films proved to be nonconductive. As such, it was concluded that although biofilms provide huge potential in the recovery and subsequent use of PGM catalysts, at present, they are unsuitable for Fuel Cell use