Rational Design of Different Morphologies of Ammonium Vanadium–Chromium Oxide Nanostructures: Mechanistic Insights and Ammonium Storage

At the nanoscale, control over size, composition, and morphology is paramount, representing the ultimate challenge in material design. In this study, we report a synthesis of ammonium vanadium-chromium oxide nanomaterials by controlling temperature and the precursor addition order. A hydrothermal process enables the formation of three distinct morphologies, nanosheets, nanowires, and nanoflowers, each exhibiting a layered structure with integrated ammonium and oxygen defects. Mechanistic studies reveal that the addition sequence influences the vanadia coordination environment, where a balanced interplay between tetrahedral and square pyramidal configurations directs the formation of either elongated or planar structures. Notably, the nanowires show enhanced specific capacitance for NH₄⁺ ion storage, underscoring the promise of these materials for supercapacitor applications and the critical impact of the synthesis protocol on nanomaterial performance.