On the viability of Mg extraction in MgMoN₂: a combined experimental and theoretical approach

Layered MgMoN₂ was prepared by solid state reaction at high temperature between Mo and Mg₃N₂ in N₂ which represents a simple synthetic pathway compared to the previously reported method that used NaN₃ as the nitrogen source. The crystal structure of MgMoN₂ was studied by synchrotron X-ray and neutron powder diffraction. The feasibility of oxidizing this compound and concomitantly extracting magnesium from the structure was assessed by both chemical and electrochemical approaches, using different protocols. The X-ray diffraction patterns of the oxidized samples do not exhibit any relevant difference with respect to that of the as prepared MgMoN₂ and no differences in the cell parameters are deduced from Rietveld refinements. No hints pointing at the presence of any amorphous phase are observed either. These results are rationalized through DFT calculated energy barriers for Mg²⁺ ion migration in MgMoN₂.