Hydrogen insertion compounds of V3O7 and V6O13: structural and thermochemical aspects

Abstract

Hydrogen insertion compounds, H_xV₃O₇(0 < x < 1.51) and H_xV₆O₁₃(0 < x < 5.82), have been prepared at ambient temperatures, both chemically, by hydrogen spillover, and electrochemically. Powder X-ray diffraction data suggest that both hydrogen insertion reactions proceed topotactically. Vibration spectra confirm that the resulting compounds can be formulated as the oxyhydroxides V₃O_7–x/2(OH)_x(x < 1.51) and V₆O_13–x/2(OH)_x(x < 5.82). The enthalpies of formation of H_xV₃O₇(x= 0.62 and 1.40) and H_xV₆O₁₃(x= 5.82) and the corresponding parent oxides have been determined by solution calorimetry. The stabilities of the insertion compounds towards decomposition, disproportionation and oxidation are discussed.