Well-aligned molybdenum oxidenanorods on metal substrates: solution-based synthesis and their electrochemical capacitor application

Abstract

In this work, we have successfully developed a mild solution-based route to elaborate well-aligned MoO₃ and MoO₂ nanorods as the electrode active materials directly on metallic current collectors for the first time. Prior to nanostructure growth, an incubation layer, containing peroxomolybdate precursors is deposited on the selected Cu foil, which has been found to play a crucial role on the oriented alignment of molybdenum oxide nanorods. The nanorod arrays are generated on the pre-treated Cu substrate by initial heterogeneous nucleation and subsequent growth from an aqueous or ethanol solution of a peroxomolybdate precursor. A good electrical transport and interaction with nanorod–Cu metal contacts are revealed by the current–voltage characteristics in this work. While such molybdenum oxide array films adhering to copper foil were employed directly as an integrative working electrode, the capacitive behaviors indicate that both molybdenum oxide array electrodes possess high specific capacitance and excellent cycle retention for electrochemical supercapacitor applications, which are investigated in detail by cyclic voltammetry and galvanostatic charge–discharge measurements at different current densities. Such enhancements are predominantly attributed to the direct lengthways electronic pathways, increased effective surface area and low contact resistance between the aligned nanorods and the Cu current collector junctions.