Hydrothermal preparation, growth mechanism and supercapacitive properties of WO3 nanorod arrays grown directly on a Cu substrate

Abstract

Well-oriented hexagonal WO₃ nanorod arrays (h-WNRs) with an average diameter of 150 ± 50 nm and a length of 2.0–3.0 μm have been successfully realized on a Cu substrate on a large scale via a simple hydrothermal method without organic additives and substrate pre-treatment. The morphology, crystallinity, atomic composition and chemical state of WNRs are investigated by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The morphology evolution and growth mechanism of well-aligned WNRs are intensively studied. Moreover, the supercapacitive properties of WNRs with different diameters and aspect ratios are also examined. WNRs exhibit excellent cycling stability and reversibility (97%), a high specific capacitance (463 F g⁻¹) at a current density of 1.0 A g⁻¹, and a lower charge transfer resistance (0.8 Ω).