Spectroscopic study of the adsorption of carbon monoxide on solutions of nickel oxide and magnesium oxide. Part 2.—Samples pretreated with hydrogen

Abstract

MgO–NiO solid solutions can be reduced by H₂ in two steps: in the first (temperature range 673–1093 K) mainly the Ni²⁺ ions located on the surface are involved, while in the second (T > 1093 K) those located in the bulk are also reduced.

The dimensions of the Ni particles formed during the reduction process increase with the temperature of reduction and with the nickel concentration on the surface. The particles formed at low temperatures are easily destroyed by CO with the formation of mononuclear and polynuclear carbonyls; particles formed at higher temperature are more resistant to CO attack.

The carbonyls formed on reduced solid solutions upon adsorption of CO are the same as those found on the unreduced (standard) samples, the only difference being the absence in the first case of the oxidized products (adsorbed carbonates).