A versatile sol–gel coating for mixed oxides on nanoporous gold and their application in the water gas shift reaction

Abstract

Based on a sol–gel coating method, a series of nanoporous gold (npAu) catalysts functionalized with titania–ceria mixed oxides were prepared. Metal-oxides with different composition were formed inside the mesoporous material (ligaments and pores ∼45 nm) after thermal treatment at over 200 °C for 2 h. The water-gas shift (WGS) reaction (H₂O + CO → H₂ + CO₂) was studied in a continuous flow reactor at ambient pressure using these Ce–TiO_x/npAu catalytic materials. Formation of CO₂ was observed at temperatures between 200 °C and 450 °C. The addition of CeO₂ to TiO₂ resulted in an strongly increased activity; the sample (with the molar ratio of Ce : Ti = 1 : 2 abbreviated as Ce₁Ti₂O_x/npAu) shows the highest activity which was nearly twice as high as the activity of all other samples at 300 °C. The loss of activity after 2 catalytic runs was only about 10% at 450 °C for the Ce₁Ti₂O_x/npAu sample and no coarsening was observed. Raman spectroscopic characterization of the materials indicates a dynamic correlation between the crystallization (oxygen storage) of the metal-oxides under oxidizing and reducing conditions.