A RAIRS, STM and TPD study of the Ni{1 1 1}/R,R-tartaric acid system: Modelling the chiral modification of Ni nanoparticles

Asymmetric hydrogenation of β-keto esters over chirally modified Ni catalysts is a rare example of a heterogeneously catalysed enantioselective process. To date, little is known on a fundamental level about the surface of Ni nanoparticles following adsorption of the chiral modifier, e.g. R,R-tartaric acid. We report an investigation of the adsorption of R,R-tartaric acid onto a model catalyst surface, Ni{1 1 1}. We show that the two-dimensional packing, molecular conformation and thermal stability of the modified surfaces are all inextricably linked and critically dependent on sample temperature, arrival rate of the modifiers at the surface and the presence or absence of coadsorbed CO. We report the formation of ordered adlayers of tartrate species whose thermal stability increases with increasing coverage and is also dependent on adsorption temperature.