Preparation of Highly Active and Thermally Conductive Platinum Nanoparticle/Ce–Zr–Y Mixed Oxide/AAO Washcoat Catalyst for Catalytic Hydrogen Combustion Technologies

A nanoparticle Pt/Ce–Zr–Y (Pt/CZY) mixed oxide/AAO washcoat catalyst was prepared and evaluated for passive autocatalytic hydrogen recombination (AAO, anodized aluminum oxide). Detailed characterization of the catalyst surface using scanning electron microscopy showed that Pt/CZY was deposited as aggregates, partly covering the AAO surface. The Pt/CZY/AAO catalyst was, therefore, tested for catalytic hydrogen combustion (1–10 vol % hydrogen in the air) at different gas flow velocities (4, 6, 8, 10, and 12 m/s) in a recombiner section testing station. The results showed that the combustion temperature and hydrogen conversion are significantly affected by the inlet conditions, such as hydrogen concentration and gas flow velocity. An accelerated durability test was performed by aging the catalyst in an oxidative atmosphere at 550, 800, and 1100 °C. During the catalytic test, the catalysts aged at 550 and 800 °C retained their catalytic activity, while the catalyst aged at 1100 °C showed no activity toward the hydrogen combustion reaction. X-ray photoelectron spectroscopy results revealed that the Pt concentration increased with increasing aging temperature while Pt oxides concentration decreased. Therefore, it was concluded that the deactivation of the catalyst aged at 1100 °C was rather caused by Pt sintering. To detect Pt particles and to confirm that Pt sintering occurred after the aging treatment at 1100 °C, transmission electron microscopy was carried out. The thermal distribution throughout the catalytic surface was investigated using an infrared camera. The Pt/CZY/AAO washcoat catalyst had high thermal conductivity─at 10 vol % hydrogen, it exhibited a temperature gradient of 22.7 °C throughout the catalyst surface.