Microstructure of highly effective platinum–iridium alloys as catalysts for hydrogen peroxide decomposition

Catalysts are widely used in research and in industrial applications to enable or to accelerate chemical reactions. One application is monopropellant thrusters for space propulsion systems, which use hydrogen peroxide (H 2 O 2 ) as liquid propellant. The decomposition of liquid hydrogen peroxide into water and oxygen gas, which then finally generates the thrust, can be achieved using noble metal catalysts like platinum and iridium. In this study, iridium–platinum alloys were deposited onto ceramic pellets by a controlled magnetron sputtering process with different parameters. Selected parameters result in coated layers featuring an atomic structure of closed- and/or open-shell microstructures. The catalytic performance of these coated pellets was evaluated in laboratory experiments. The reactivity of sputtered iridium–platinum layers for the decomposition of H 2 O 2 was found to be significantly higher with respect to layers of pure iridium coatings. This can be explained by the better reactivity of iridium–platinum alloys, combined with the active control of the surface morphology and the microstructure of the alloy coatings. Graphical abstract