Cu/CeO<sub>2</sub> and Cu/Gd-Substituted CeO<sub>2</sub> Aerogels as Active, Selective, and Stable COPROX Catalysts
Travis G. Novak, Paul A. DeSario, Todd Brintlinger, Ryan H. DeBlock, Jeffrey W. Long, Debra R. Rolison
Abstract
Purifying hydrogen feedstocks necessitates preferential oxidation of carbon monoxide (COPROX), but traditional precious metal catalysts are poorly selective, while transition metal catalysts suffer from insufficient activity and stability. We report that Cu nanoparticles supported on CeO 2 or Gd(III)-substituted CeO 2 (GCO) aerogels deliver a rare combination of high activity, selectivity, and stability for COPROX. The reducing oxide disperses Cu and stabilizes its more active low-valent state. Aerogel-supported Cu oxidizes CO at low temperature but requires higher temperatures to oxidize H 2 and, therefore, shows wide temperature ranges with >95% CO conversion and >95% selectivity vs H 2 . This performance is maintained for >16 h of continuous operation in dry or humidified reaction streams. The Cu/GCO aerogel is less active than Cu/CeO 2 under dry feedstreams but experiences less loss of activity under humid conditions because the higher surface area of the former distributes surface-adsorbed water along the network and reacts it at oxygen vacancies. Aerogel-based architected catalysts offer an effective design route to achieve high and stable catalytic activity under industrially relevant conditions.