Mapping Support Interactions in Copper Catalysts

Intrinsic activity is often reported as a Turnover Frequency (TOF) of an active phase and is determined from an overall activity and a specific active surface area. The latter parameter is often determined by selective chemisorption techniques, but (strong) metal-support interactions, (S)MSI, between the metal and the carrier in an interplay with the nature of the probe molecules may distort the measurements. Here, a double-area-estimation approach is used for fast and accurate evaluation of (S)MSI effects in supported Cu catalysts: Firstly, baselines for the Temperature Programmed Desorption of Hydrogen (H₂-TPD) and Reactive Frontal Chromatography by Nitrous oxide (N2O-RFC) methods commonly used to titrate Cu areas were established by comparison with Brunauer-Emmett-Teller (BET) surface areas using a series of pure Cu catalysts. Pure unsupported Cu samples, free from support interactions, were used to determine the stoichiometries between the probe molecules, H₂ and N₂O, and Cu surface atoms. This resulted in values of 2.08 ± 0.14:1 (Cu:O) and 2.81 ± 0.09:1 (Cu:H2). Cu on a wide range of support materials were subsequently analyzed by H₂-TPD and N₂O-RFC and benchmarked according to the unsupported Cu reference. This was done to study metal support interactions and increase the understanding of the nature of the interactions between Cu and different carriers.