Synthesis of Copper Phosphide Nanotube Arrays as Electrodes for Asymmetric Supercapacitors

A copper(I) phosphide (Cu3P) nanostructure with tubelike morphology has been directly synthesized on copper foil via a two-step process of electro-oxidation and phosphidation. The microstructure and morphology of the Cu3P nanotube (NT) arrays are systematically examined with the measurements of a SEM, a TEM, XRD, and XPS. Electrochemical measurements manifest that the Cu3P NT exhibits excellent properties of a negative electrode of a supercapacitor. An optimized asymmetric supercapacitor with a negative electrode of Cu3P NT and a positive electrode of CNT has been fabricated that can deliver energy density of 44.6 Wh kg(-1), power density of 17 kW kg(-1), and stability test with over 81.9% of specific capacitance remaining after 5000 cycles; these features are valuable for prospective applications of Cu3P NT in systems for energy storage and conversion. This work paves the way to explore phosphide-based materials in a new class for supercapacitor applications.