Surface chemistry of catalysis by gold

Gold has long been regarded as an inert surface and bulk gold surfaces do not chemisorb many molecules easily. However, in the last decade, largely through the efforts of Masatake Haruta, gold particles, particularly those below 5 nm in size, have begun to garner attention for unique catalytic properties (1-8). In recent years, supported gold particles have been shown to be effective as catalysts for low temperature CO oxidation (9), selective oxidation of propene to propene oxide (10), water gas shift (11), NO reduction (12). selective hydrogenation of acetylene (or butadiene) (13) and other reactions (1-5,14-16). Currently used in Japanese toilets for odour reduction (3), gold has demonstrated industrial potential as well for the hydrochlorination of ethyne to vinyl chloride (16-18) and as a bimetallic component of vinyl acetate monomer production catalysts (19,20). Low temperature CO oxidation is of particular importance, finding applications in indoor air quality applications (21) and as a guard bed catalyst to prevent CO poisoning of proton exchange membrane fuel cells (22-24).