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Understanding leads to optimisation

EU-funded scientists made detailed characterisations of ion mobility and conductivity in promising fuel cell materials. The optimisation of these properties should enhance the widespread uptake of emissions-free fuel cell technology.
Understanding leads to optimisation
Fuel cells are electrochemical conversion devices that can use a variety of different fuels and produce harmless by-products such as heat and water. Like batteries, they convert chemical energy directly into electrical energy without the combustion process and the undesirable emissions that contribute to global climate change. Thus, fuel cells are one of the main pillars of the EU's alternative energy programme.

The main fuel cell components are two electrodes (anode and cathode) and an electrolyte or ion-conducting medium between them. The hydrogen-rich fuel participates in a chemical reaction at the anode to produce electrons and ions. The electrons are directed through an external circuit to the cathode and the ions traverse the electrolyte to participate in a reaction with oxygen at the cathode. The nature of the electrolyte largely determines the type of fuel cell.

Solid-oxide fuel cells (SOFCs), as the name suggests, use a solid electrolyte. SOFCs are among the most promising fuel cell technologies but optimisation depends largely on increasing the electrolyte conductivities of hydrogen ions or protons (H+) and oxygen ions (O2-). EU-funded scientists working on the NMRSOFC project employed nuclear magnetic resonance (NMR) spectroscopy, the most powerful structural determination technique available, to study H+/O2- dynamics in an operating SOFC.

Detailed NMR studies of the electrolyte material yttrium (Y)-doped barium zirconate (BZY) demonstrated that proton transport limitations are due to a phenomenon called proton trapping. Similar studies of caesium hydrogen phosphate (CsH2PO4) elucidated complex mechanisms of proton transport and relationships to temperature changes. Experimental NMR investigations together with mathematical modelling highlighted mechanisms affecting both oxygen and hydrogen mobility in hydrated Y-doped barium stannate (BaSn1-xYxO3-x/2). Scientists also published an important paper reporting a method to increase the resolution of NMR spectroscopy.

SOFCs are an important part of the EU's programmes to develop renewable energy alternatives to the combustion of fossil fuels. They are highly efficient, silent and emissions free, and can use a variety of hydrogen-rich fuels. NMRSOFC scientists made a significant contribution to SOFC optimisation by characterising ion transport in promising solid electrolytes that should promote widespread market uptake.

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