The leaching-activation process of Urushibara catalysts

The acid-leaching process resulting in the activation of Urushibara-Ni catalysts was studied by means of X-ray photoelectron spectroscopy (XPS), X-ray diffraction, scanning electron microscopy (SEM) combined with X-ray energy dispersion (EDX), and wet chemical analysis. The leaching-induced activation has been shown to involve the dissolution of a coating surface layer dominated by zinc compounds and the exposure of metallic nickel. Metallic zinc coexisting with the nickel on the activated surface prevents (at low oxidation doses) the oxidation of the inherently active nickel, by gettering the oxidizing molecules. Exposing the active surface to high oxidation doses results in the oxidation of both metallic constituents and the loss of catalytic activity.