Water–Gas Shift Reaction Over Aluminum Promoted Cu/CeO₂ Nanocatalysts Characterized by XRD, BET, TPR and Cyclic Voltammetry (CV)

Abstract

A series of aluminum promoted Cu/CeO₂ nanocatalysts with aluminum content in the range of 0–5wt.% were prepared by co-precipitation method and examined with respect to their catalytic performance for the water–gas shift (WGS) reaction. The catalysts were characterized by XRD, BET, H₂-TPR and cyclic voltammetry (CV) techniques. The results indicate that catalytic activity increases with the aluminum content at first, but then decreases with the further increase of aluminum content. Hereinto, Cu/CeO₂ catalyst doped with 1 wt.% of aluminum shows the highest catalytic activity (CO conversion reaches 84.4% at 200 °C) and thermal stability for WGS reaction. Correlation to the results from above characterization, it is found that the variation of catalytic activity is in very agreement with that of the surface area, the area of peak γ (i.e., the reduction of surface copper oxide (crystalline forms) interacted with surface oxygen vacancies on ceria), and the area of peak C₂ and $\hbox{A}_{1} (\hbox{Cu}^{0}\,\leftrightarrow\,\hbox{Cu}^{2+}$ in cyclic voltammetry process), respectively. Enough evidence was found for the fact that the metallic copper (Cu⁰) interacted with surface oxygen vacancies on ceria is the active site for WGS reaction over Cu/CeO₂ catalysts.