4 Search Results

The strong metal-support interaction (SMSI) for supported Ni/CeO₂ catalysts with different CeO₂ nanomorphologies was systematically explored. The degree of encapsulation of Ni particles originating from the SMSI effect was found to follow the trend of Ni/CeO₂-(1 1 1) > Ni/CeO₂-(1 0 0) > Ni/CeO₂-(110 + 100), which parallels the CO₂ hydrogenation activity. Quasi in situ XPS reveals the presence of Ce³⁺ sites in accordance with the formation of an amorphous surface CeOx layer encapsulating the Ni nanoparticles. In situ DRIFTS indicates the reaction pathway and rate-determining step are dependent on the degree of the SMSI effect, leading to distinct selectivitiesmore » towards CH₄, especially at a high weight hourly space velocity (WHSV). Finally, these findings present a fundamental strategy about tailoring catalytic performance through support facet dependent susceptibility of SMSI phenomena.« less

The influence of basic oxide promoters on copper-chromium-iron oxide catalysts was investigated to determine the nature of surface oxygen species and structure-activity relationship for the reverse water-gas shift reaction. The catalysts were characterized with in situ XRD, in situ Raman, in situ XPS, in situ HS-LEIS and H₂-TPR. Two surface oxygen sites with different reduction characteristics were found to be present. The overall CO₂ activation rate was found to correlate with both the number and reducibility of the more active oxygen species that were likely associated with the Cu-FeO_x interfacial regions for enhanced hydrogen spillover. While addition of K₂O somewhatmore » preserved the interfacial regions and facilitated the reduction kinetics of surface oxygen, both Na₂O and CaO significantly suppressed the availability of metallic Cu as well as the Cu-FeO_x interfaces, leading to decreased reactivity. These findings provide a direction to promote the copper-iron catalysts by creating more metal-metal oxide interfacial sites.« less

Abstract The commercial high‐temperature water‐gas shift (HT‐WGS) catalyst consists of CuO‐Cr ₂ O ₃ ‐Fe ₂ O ₃ , where Cu functions as a chemical promoter to increase the catalytic activity, but its promotion mechanism is poorly understood. In this work, a series of iron‐based model catalysts were investigated with in situ or pseudo in situ characterization, steady‐state WGS reaction, and density function theory (DFT) calculations. For the first time, a strong metal‐support interaction (SMSI) between Cu and FeO _x was directly observed. During the WGS reaction, a thin FeO _x overlayer migrates onto the metallic Cumore » particles, creating a hybrid surface structure with Cu‐FeO _x interfaces. The synergistic interaction between Cu and FeO _x not only stabilizes the Cu clusters, but also provides new catalytic active sites that facilitate CO adsorption, H ₂ O dissociation, and WGS reaction. These new fundamental insights can potentially guide the rational design of improved iron‐based HT‐WGS catalysts.« less

Abstract The commercial high‐temperature water‐gas shift (HT‐WGS) catalyst consists of CuO‐Cr ₂ O ₃ ‐Fe ₂ O ₃ , where Cu functions as a chemical promoter to increase the catalytic activity, but its promotion mechanism is poorly understood. In this work, a series of iron‐based model catalysts were investigated with in situ or pseudo in situ characterization, steady‐state WGS reaction, and density function theory (DFT) calculations. For the first time, a strong metal‐support interaction (SMSI) between Cu and FeO _x was directly observed. During the WGS reaction, a thin FeO _x overlayer migrates onto the metallic Cumore » particles, creating a hybrid surface structure with Cu‐FeO _x interfaces. The synergistic interaction between Cu and FeO _x not only stabilizes the Cu clusters, but also provides new catalytic active sites that facilitate CO adsorption, H ₂ O dissociation, and WGS reaction. These new fundamental insights can potentially guide the rational design of improved iron‐based HT‐WGS catalysts.« less