Pechini synthesis and characterization of molybdenum carbide and nickel molybdenum carbide

Abstract

Carbides, such as η-Ni 6Mo 6C, are considered as low-cost substitutes for noble metal catalysts for present applications in hydrodesulfurization and for a possible future sulfur-tolerant fuel cell anode catalyst. Most synthesis methods set the carbon content of the carbides by a carbon-based atmosphere or solid carbon in the synthesis. We show here that β-Mo 2C and η-Ni 6Mo 6C can be synthesized using a Pechini process, simply by heating metal acetates mixed with citric acid and ethylene glycol in one step under H 2 with the only source of carbon being the precursor solution. The β-Mo 2C forms when heating a Mo-acetate precursor at 850 °C. When using Ni- and Mo-acetates, β-Mo 2C forms at 700 °C and lower temperatures, while η-Ni 6Mo 6C forms during heating at 800–900 °C. The η-Ni 6Mo 6C has a surface area of 95.5 m 2 g −1 and less than 10 m 2 g −1 when prepared at 800 and 900 °C, respectively. Some Ni 3C, Ni, and NiC impurities are also present in the nanostructured η-Ni 6Mo 6C that was prepared at 900 °C. The η-Ni 6Mo 6C materials made by the Pechini process are compared with those made from a traditional synthesis, using metal organic precursors at 1000 °C under CO/CO 2 mixtures with a carbon activity of 0.011. Our results imply that H 2 and the Pechini process can be used to achieve carbon activities similar to those obtained by methods using gaseous or solid carbon sources.