Mixed ion and electron conductive ceramic materials, like perovskites, are under investigation as membranes for gas separation at high temperature by many groups. However while pure proton conductive membranes like Nafion are also topic of worldwide research, polymeric proton-electron mixed conductive materials have been not much explored. Important requirements for an effective mixed conduction composite membrane are:
- percolation of the electron conductive particles, keeping the conductivity as high as possible;
- good adhesion between the proton and electron conductive phases;
- fine dispersion of fillers;
- direct accessibility or even covalent attachment of the catalyst both to electron and conductive components.
Aim of the research is to design and fabricate a semi-permeable membrane, made from ionomers with two essential functions: separation of reactants and transport of protons and electrons. The transport of both electrons and protons will be enabled via carbon nanotubes (CNT) or TiO2 and ion-exchange resins like Nafion, respectively. Nafion can play a role both as catalyst support and as solvated proton conductor (like in PEM fuel cells). These membranes will be used in a nano-designed reactor for splitting water to produce hydrogen at ambient temperature. The membrane will provide transport of electric charge: it will catch the protons where they are generated and drive them towards the cathode where H2 will be formed, due to the injection of excited electrons derived from the chlorophyll-dependent photo-activated water splitting reaction. Finally, the membrane will have to be tailored to provide the minimum transfer resistance so as to achieve maximum conversion efficiencies: a MEA (membrane-electrode-assembly) structure will be studied on purpose.
This research line is carried out in combination with a fundamental research laboratory (Biosolar Lab) just get on the ground at PoliTO's site in Alessandria and led for the next three years by one of the most reputed scientists in the field (Prof. James Barber, formerly at the Imperial College London, ENI Italgas prize in 2005 for his high-precision understanding of the Photosystem II).
Electrical conductivity measurements and FESEM image of a Nafion membrane with dispersed CNTs
Tel. +39 011 564 7379
Stefano Bianco, Mauro Tortello, Angelica Chiodoni, Giancarlo Cicero, Marzia Quaglio
Partners and Projects
FP7 - EU Project "Solhydromics: "Nanodesigned electrochemical converter of solar energy into hydrogen hosting natural enzymes or their mimics" (coordinator G. Saracco, POLITO)