Determining Number of Active Sites and TOF for the High-Temperature Water Gas Shift Reaction by Iron Oxide-Based Catalysts

This study demonstrates, with (CO2)-O-16/(CO2)-O-18 isotope switch and H-2-TPR experiments, for the first time that (i) the high-temperature water gas shift (HT-WGS) reaction by copper-chromium-iron oxide catalysts follows a redox mechanism dominated by the surface layer, (ii) the number of catalytic active sites can be quantified by the isotopic switch, and (iii) the turnover frequency (TOF) can be determined from knowledge of the number of sites. The quantitative TOF values reveal that chromium is only a textural promoter, whereas copper is a chemical promoter.