Metal(-oxide) catalyst-monolayer as cost-effective electrocatalysts for PEM water electrolysis

Water electrolysis is a method for producing hydrogen, a fuel, from renewable energy and water. One of the most compact and energy efficient water electrolysis technologies, so-called PEM water electrolysis, relies on costly and scares iridium metal. It is therefore important to make catalysts that utilizes the iridium metal to the fullest exten. Since only the surface is catalytically active, the purpose of the project is to make a catalyst with a thin layer of iridium deposited at a cheaper and inert substrate material. This would give the maximum catalytic activity per gram of iridium. Project results: 1. Nickel of copper metal is depostied on a cheaper and inter substrate material (an oxide or a metal). 2. The copper or the nickel is exchanged with iridium in a so-called galvanic process. 3. Since the substrate material is chosen so that it will not exchange galvanically with iridium, the process will stop once all the sacrificial metal (copper or nickel) has been consumed. 4. The thickness of the resulting iridium layer is therefore determined by the thickness of the sacrificial metal layer. 5. If nickel is used, this results in an arbitratily thick nickel layer. The process based on nickel is known from before. 6. Copper can, at certain substrates, be deposited so that the layer is only one atom thick. 7. If this copper layer is exchanged with iridium, the iridium layer will be correspondingly thin. 8. Galvanic exchange between iridium and copper is a result of the work at NTNU. 9. This knowledge has been used as input for the SINTEF activity, whose part has been to synthesize oxidic substrate materials containing copper (or nickel) as the sacrificial metal. 10. In this last phase of the project we are making nanostructured catalysts based on galvanic exchange of copper with iridium (metal substrates) and nickel (oxides) for PEMwater electrolysis. 11. A number of publications/manuscripts reporting the results are in the process of being written. (One manuscript has been submitted.) 12. Successful deposition of Pt nanoparticles directly onto oxide supports by galvanic replacement with Cu, as well as for iridium with nickel. 13. Investigations of the effect of polyvinylpyrrolidone (PVP) stabilization to tailor the size and distribution of the Pt nanoparticles onto the oxide support. Successful verification of excellent activity and durability of such catalysts. 14. One PhD candidate has been educated.

Virkninger for prosjektets deltagere: Prosjektets deltagere har lært seg en ny metode for framstilling av ultratynne belegg som kan benyttes også for andre typer anvendelser enn elektrokatalyse. Dette vil i sin tur danne grunnlag for nye søknader (EU og andre) og nytt samarbeid med katalysator-industrien. (Gupperingen er nylig tildelt et nytt katalysatorprosjekt.) Prosjektet har også utdannet en PhD kandidat som nå er ansatt i elektrokjemisk industri (batteri). NTNU er i ferd med å oppskalere metoden slik at det kan produseres katalytiske sjikt basert på katalysatorene utviklet det i prosjektet. Virkninger for brukere: Det har ikke verdt noen utførende partnere i prosjektet som representerer brukere. Effekten for brukere vil derfor i første omgang være knyttet til arbeid samarbeid i andre prosjekter. Lykkes framstillingen av katalysatorer på gram-skala vil vi kunne levere katalysatorer til brukere for uttesting på pilotskala.

Efficient water electrolysis is a requirement for a transition to a hydrogen-based energy system. Therefore, the MOxiLAYER project adresses the ENERGIX thematic area Energy use and conversion directly by contributing to a potential reduction in the capital costs and an increase in the energy efficiency of PEM water electrolysers for production of hydrogen from renewable electricity. This project deals with water electrolysis with proton-conducting membranes. Due to the acidic conditions in these membranes the oxygen evolution reaction at the anode is slow and requires use of expensive and scarce materials for electrocatalysts which will hamper the use of this otherwise efficient technology. Thus, the project introduces new concepts in the development of highly active electrocatalysts for PEM electrolysers and will lead to a potential 75% reduction of the use of platinum group metals compared to the state of the art PEM electrolysers. The project draws on recent experimental and theoretical progress to solve this problem by designing and implementing catalyst architectures of ultra-high catalyst utilization. Among other things, work performed at NTNU and SINTEF indicates that the relevant metal oxide catalysts applied as thin catalyst surface layers on an appropriate substrate will be largely unaffected by the exact nature of the substrate, and that these segregated structures will perform as well as the corresponding bulk catalyst made of the surface layer material. The project thus pursues the use of wet-chemical synthesis techniques, suitable for up-scaling, to achieve catalyst architectures such as MOx@IrO2 core@shell catalysts based on iridium oxide shells and a conducting oxide cores. This will be combined with advanced characterization techniques for verification of the structures as well as their implementation in electrolysis cells in test stations at the Norwegian Fuel Cell and Hydrogen Centre.