A new approach to the synthesis of molybdenum bimetallic nitrides and oxynitrides

Abstract

A simple processing route to molybdenum bimetallic nitrides and oxynitrides has been developed, based on the use of precursors resulting from freeze-drying of aqueous solutions of the appropriate common metal salts. Thermal decomposition of amorphous freeze-dried powders originates crystalline mixed oxides, which have been carefully characterized. Nitridation of the crystalline intermediate having Ni:Mo=2:3 metal ratio led to single-phased Ni ₂ Mo ₃ N. For the V-Mo-O-N system, nitridation of both amorphous and crystalline precursors results in bimetallic oxynitrides. In this way, not only the already known V ₂ Mo(O _x N _y ) catalyst but also a new compound of different metal stoichiometry, V ₃ Mo ₂ (O _x N _y ), has been prepared. The materials have been characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy, thermogravimetry under air flow, and temperature programmed oxidation. The existence of a solid solution of stoichiometry V _1–z Mo _z (O _x N _y ) (0≤z≤1) having rock-salt structure is discussed.