Solution Combustion Synthesis and Characterization of Magnesium Copper Vanadates

Abstract

Magnesium vanadate (MgV2O6) and its alloys with copper vanadate were synthesized via the solution combustion technique. Phase purity and solid solution formation were confirmed by a variety of experimental techniques, supported by electronic structure simulations based on density functional theory (DFT). Powder X-ray diffraction combined with Rietveld refinement, laser Raman spectroscopy, diffuse reflectance spectroscopy, and high-resolution transmission electron microscopy showed single-phase alloy formation despite the MgV2O6 and CuV2O6 end members exhibiting monoclinic and triclinic crystal systems, respectively. DFT-calculated optical band gaps showed close agreement in the computed optical bandgaps with experimentally derived values. Surface photovoltage spectroscopy, ambient-pressure photoemission spectroscopy, and Kelvin probe contact potential difference (work function) measurements confirmed a systematic variation in the optical bandgap modification and band alignment as a function of stoichiometry in the alloy composition. These data indicated n-type semiconductor behavior for all the samples which was confirmed by photoelectrochemical measurements.

Synthesis and Tuning of Electronic, Optical, and Photoelectrochemical Properties of Copper Metavanadate Alloys via Alkaline Earth Metal Substitution

“…These findings suggest that SCS can produce phase-pure products, consistent with our previous findings on the Cu-V-O family. 1,16 The PXRD patterns for the synthesized compounds are shown in Fig. 2.…”

“…In this paper, as in our companion report, 1 we develop this theme further both experimentally and theoretically and explore the added effect of alkaline metal incorporation specifically into the CuV 2 O 6 host framework. New data on alloying with Ca are presented here along with the Mg alloy previously reported 1 for the CuV 2 O 6 host framework.…”

“…Our prior experience 1,15,16 with the Cu-V-O compound family had bolstered the notion that Cu incorporation would lower the energy bandgap and thereby improve visible light absorption of the vanadium oxide parent framework. In this paper, as in our companion report, 1 we develop this theme further both experimentally and theoretically and explore the added effect of alkaline metal incorporation specifically into the CuV 2 O 6 host framework. New data on alloying with Ca are presented here along with the Mg alloy previously reported 1 for the CuV 2 O 6 host framework.…”

“…The corresponding property variations were expanded to include structural and morphological aspects of the alloys in both the Ca and Mg cases. As in our previous report, 1 these alloys were synthesized by solution combustion synthesis (SCS), a hitherto unprecedented synthesis candidate for ternary copper vanadates except in our group. Thus, the SCS of the copper end member (CuV 2 O 6 ) as well as the magnesium end member (MgV 2 O 6 ) was described by us previously.…”

“…Thus, the SCS of the copper end member (CuV 2 O 6 ) as well as the magnesium end member (MgV 2 O 6 ) was described by us previously. 1 The level of alkaline earth metal (A) incorporation was kept below ∼10% in this study so as not to exceed the limit of solubility of the "foreign" cation, A as borne out by preliminary experiments.…”