Surface protonics for oxide-based electrochemical energy devices

In the transition to a low-emission society based on renewable energy, new knowledge and innovative solutions are required that promote long-term development of the energy system. This development involves more use of renewable energy resources (wind, solar and hydropower), more energy efficient solutions and increased need for flexibility. Two important devices in the energy system will be fuel cells and electrolysers. In a fuel cell, hydrogen gas is converted into electricity, while in an electrolyser the opposite occurs - electricity is used to produce hydrogen gas from water. In the research project SUPROX we have investigating a new type of materials for such fuel cells and electrolysers. These new materials are porous ceramic materials that have a thin layer of water on the surface. Fuel cells and electrolysers depend on protons, which are positively charged hydrogen atom cores, being transported through a membrane. In the porous ceramic materials, the transport of protons occurs in the water layer on the surface. The fuel cells used most today, for example in hydrogen cars, are based on polymeric materials that do not withstand elevated temperatures and contain a lot of expensive platinum. The new materials we have developed in SUPROX can potentially make the fuel cells and electrolysers cheaper and more robust in the future compared to current solutions. We have screened many potential materials as electrodes and electrolytes and have worked on optimizing the fabrication of fuel cells based on the most promising materials. Electrochemical testing of surface protonic fuel cells based on zeolite film as the porous electrolyte showed that the resistance in the electrolyte layer was relatively low, but that the current output was limited due to high resistance of the electrode processes. Operation temperatures above 100 °C has been tested and proven beneficial to reduce water condensation. The understanding of adsorption and dissociation of water and migration of protons on internal surfaces of nanoscopic porous oxides has been greatly increased by the development of quantifiable models. The improved understanding of surface protonics can also give improved understanding of catalytic processes, for instance on CeO2, and may open up for applications also within catalysis. The project arranged the 1st International workshop on surface protonics (SUPR01) in March 2022. SUPROX was a collaboration between SINTEF and the University of Oslo and was funded by The Research Council of Norway's ENERGIX program.

Prosjektet har i stor grad bidratt til å utvikle forskningsfeltet "overflateprotonikk" (engelsk: "surface protonics") ved: (1) utvikling av kvantifiserbare modeller for adsorpsjon og dissosiasjon av vann og migrering av protoner på indre overflater av nanoskopiske porøse oksider, (2) fabrikasjon av brenselceller basert på overflateprotonisk ledning og demonstrasjon av disse, og (3) ved å arrangere den første internasjonale workshopen om overflateprotonikk (SUPR01) i mars 2022.

The project "Surface protonics for oxide-based electrochemical energy devices" (SUPROX) aims to develop the next generation fuel-flexible electrochemical cells based on surface protonic conduction in the adsorbed water layer on nanoporous ceramics. Surface protonics enable cheap and robust solid-liquid nanocomposites with high proton conductivity and chemical stability. Operating temperatures above 100 °C may alleviate current issues with water management and slow electrode kinetics and may thus mitigate the need for expensive Pt-group metal electrodes. The oxide-based nanocomposites may also enable a simpler (single chamber) and more fuel-flexible electrochemical cell which can convert cheaper low-concentration fuel mixtures (e.g. dilute biogas) into electricity in a cost-efficient manner. Novel electrolytes and electrodes for fuel cell assemblies working at 100 °C and above will be developed based on nanoporous oxides. These robust fuel cells will, when fully optimized, enable efficient use of hydrogen to produce electrical energy. The target in SUPROX is a total resistance of the cell of < 1 Ohm cm^2 at 100 °C and 50% relative humidity.