Solid-state interactions in Li-doped Ni/MgO catalysts

Abstract

The effects of the addition of Li (Li_at:Ni_at ≈ 1:3) on the structure and reducibility of a 19% Ni/MgO catalyst, calcined at T_C 400–800 °C, have been investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), temperature-programmed desorption and reduction (TPD and TPR) and transmission electron microscopy (TEM). Li causes melting of the MgO matrix, markedly altering the morphology of the Ni/MgO catalyst. Li enhances the diffusion of Ni ions into the MgO lattice and the consequent formation of an Ni_xMg_(1−x)O solid solution. Li also promotes the reduction of the Ni/MgO system, enabling easier extraction of Ni²⁺ ions located in the MgO lattice. Solid-state interactions accounting for marked changes in both the physico-chemical properties and the reactivity of the Li-doped Ni/MgO catalyst are highlighted.