Morphology-Dependent Properties of Cu/CeO2 Catalysts for the Water-Gas Shift Reaction

Abstract

CeO 2 nanooctahedrons, nanorods, and nanocubes were prepared by the hydrothermal method and were then used as supports of Cu-based catalysts for the water-gas shift (WGS) reaction. The chemical and physical properties of these catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N 2 adsorption/desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), hydrogen temperature-programmed reduction (H 2 -TPR) and in situ diffuse reflectance infra-red fourier transform spectroscopy (DRIFTS) techniques. Characterization results indicate that the morphology of the CeO 2 supports, originating from the selective exposure of different crystal planes, has a distinct impact on the dispersion of Cu and the catalytic properties. The nanooctahedron CeO 2 catalyst (Cu-CeO 2 -O) showed the best dispersion of Cu, the largest amount of moderate copper oxide, and the strongest Cu-support interaction. Consequently, the Cu-CeO 2 -O catalyst exhibited the highest CO conversion at the temperature range of 150-250 • C when compared with the nanocube and nanorod Cu-CeO 2 catalysts. The optimized Cu content of the Cu-CeO 2 -O catalysts is 10 wt % and the CO conversion reaches 91.3% at 300 • C. A distinctive profile assigned to the evolution of different types of carbonate species was observed in the 1000-1800 cm −1 region of the in situ DRIFTS spectra and a particular type of carbonate species was identified as a potential key reaction intermediate at low temperature.

Recent Advances on the Rational Design of Non-Precious Metal Oxide Catalysts Exemplified by CuOx/CeO2 Binary System: Implications of Size, Shape and Electronic Effects on Intrinsic Reactivity and Metal-Support Interactions

“…However, not all methods lead to particles of well-ordered size and shape with uniform dispersion on the catalyst surface [145]. Among the different methods, the hydrothermal one has attracted considerable attention, due to the simplicity of the precursor compounds used, the short reaction time, the homogeneity in morphology, as well as the acquisition of various nanostructures, such as rods, polyhedra, cubes, wires [107,117,121,124,131,134,135,[146][147][148][149][150][151][152][153][154][155][156][157][158][159]. Ceria nanocrystals have three low-index lattice facets of different activity and stability, namely, {100}, {110}, {111} [48,106], as shown in Figure 6.…”

“…Moreover, their excellent reactivity-linked to peculiar metal-support interactions-in conjunction to their remarkable resistance to various substances, such as carbon dioxide, water and sulfur is of particular fundamental and practical importance [57,76,204]. Remarkably, copper-containing ceria catalysts appropriately adjusted by the aforementioned routes demonstrated catalytic activity similar or even better than NMs-based catalysts in various applications, such as CO oxidation, the decomposition of N 2 O and the water-gas shift reaction, among others [115,124,159,[205][206][207][208][209][210][211][212][213][214][215][216].…”

Cu/CeO2 Catalyst for Water‐Gas Shift Reaction: Effect of CeO2 Pretreatment

“…Many efforts have been focused on uncovering the effect of CeO 2 chemical‐physical properties on the performance of Cu catalysts in the WGS reaction . The morphology and exposed crystal planes of CeO 2 were reported to have distinct impacts on dispersion and catalytic properties of Cu . For example, metallic Cu stability and Ce 3+ concentration are under the influence of CeO 2 morphology .…”

Hydrogen-Etched TiO2−x as Efficient Support of Gold Catalysts for Water–Gas Shift Reaction

“…To develop new and more efficient WGS catalysts, supported catalysts have been believed to be good candidate. For example, both precious metals (e.g., Pt, Au, Pd, Rh, Ir or Ru) [2,3] and cheap transition metals (e.g., Cu or Ni) [4,5] were deposited on various supports including TiO 2 [6][7][8][9][10][11][12][13][14][15][16][17], CeO 2 [18][19][20][21][22][23], Mo 2 C [24][25][26], FeO x [27][28][29], Co 3 O 4 [30], Al 2 O 3 [31,32], ZrO 2 [33,34], CeO 2 -TiO 2 [35], CeO 2 -ZrO 2 [36,37] and CeO 2 -La 2 O 3 [38]. Au-TiO 2 catalysts have been given considerable attentions for WGS activities, due to the high activity and low side reactions of dispersed Au [38], and some advantages of TiO 2 supports (e.g., low price, easy preparation, adjustable properties and strong interaction with active metal).…”