Carbon Monoxide Boosts Gold Catalysis

Carbon monoxide adsorbed on gold enhances the precious metal’s ability to catalyze oxidation of alcohols in an electrochemical cell, according to researchers at Leiden University, in the Netherlands (Nat. Chem., DOI: 10.1038/nchem.1221). CO is a classic example of a poison to many transition-metal catalysts because it typically binds strongly to metal active sites, denying access to reactant molecules. Not only does the study add to the growing list of catalytic transformations mediated by gold, long considered an inert material, but it also suggests “an unexpected and counterintuitive role for CO in electro-oxidation reactions, namely that of catalyst promoter,” says Marc T. M. Koper, who led the study. Paramaconi Rodriguez, Youngkook Kwon, and Koper found that for a gold electrode immersed in an aqueous alkaline solution, the minimum applied potential required to oxidize methanol (mainly to formaldehyde and formic acid) is significantly lower when CO is adsorbed on the gold than when it is absent. The team studied reactions of various alcohols and proposes that CO’s presence promotes binding of OH species, which catalyze a key hydrogen elimination step in alcohol oxidation.