Synthesis and Characterization of Magnesium Vanadates as Potential Mg-ion Cathode Materials Through an Ab Initio Guided Carbothermal Reduction Approach

Many technologically relevant transition metal oxides for advanced energy storage and catalysis feature reduced transition metal (TM) oxides and are often nontrivial to prepare because of the need to control the reducing nature of the atmosphere in which they are synthesized. In this work, we show that an ab initio predictive synthesis strategy can be used to produce multiple gram-scale products of various MgVxOy-type phases (δ-MgV2O5, spinel MgV2O4, and MgVO3) containing V3+ or V4+ relevant for Mg-ion battery cathodes. Characterization of these phases using 25Mg solid-state NMR spectroscopy illustrates the potential of 25Mg NMR for studying reversible magnesiation and local charge distributions. Rotor-Assisted Population Transfer is used as a much needed signal-to-noise enhancement technique. The ab initio guided synthesis approach is seen as a step forward towards a predictive synthesis strategy for targeting specific complex TM oxides with variable oxidation states of technological importance.

Oxidative Dehydrogenation of Cyclohexane over Mg-V-O Catalysts Prepared via Citriate Complexation

Oxidative dehydrogenation of cyclohexane was studied over three pure Mg-V-O catalysts, which are Mg3(VO4)2, Mg2V2O7and MgV2O6, respectively. Catalysts were prepared via citric acid complexation and characterized by N2-adsorption, XRD, FT-IR, NH3-TPD and H2-TPR techniques. Among the pure magnesium vanadates, Mg3(VO4)2has the isolated active sites, weakly basic surface and lower reducibility of the metal cations, and could be recognized as the catalytic active phase. Mg3(VO4)2catalyst exhibited a better catalytic performance, on which a cyclohexene selectivity of 41.5% at cyclohexane conversion of 15.5% was obtained.