On the crystal growth of vanadyl hydroxide (VOOH) with six-fold arms morphology

Fundamental understanding of microstructure evolution during nucleation and growth of ternary materials is of utmost importance for the development of the next generation of functional devices. Case in point, growth of semiconducting particles with six-fold symmetry, star-shaped, could serve as an innovative morphology for application in neuromorphic, energy storage, and heterogenous catalysis devices. Herein, we present the discovery of how the synthetic route to produce orthorhombic star-shaped vanadyl hydroxide (VOOH) by using a hydrothermal reaction of orthovanadate and thioacetamide in an alkaline solution is highly dependent on time. For example, we observe that at 36 h, we produce VS₂ nanosheets with VOOH at the surface. A 60 h of reaction produce VOOH rods clustered in a single nucleating point and at 84 h of reaction VOOH stars can be observed in combination of clustered materials. Our current hypothesis stands that the clustered rods are a product of a condensation reaction between the vanadate precursor whereas the stars are seeded by the hexagonal symmetry of VS₂ and further oxygenation and reduction of the vanadium center. Furthermore, we also elucidate the fundamental electrochemical behavior of these nanoparticles as capacitive electrodes for sodium-ion devices.