Effect of isoelectronic tungsten doping on molybdenum selenide nanostructures and their graphene hybrids for supercapacitors

Abstract

Electrochemical supercapacitors are vital for the advancement of energy storage devices. Herein, we report the synthesis of molybdenum selenide (MoSe2), tungsten-doped molybdenum selenide (WMoSe2) and their graphene (G) composites (WMoSe2/G) via a facile hydrothermal method. Physiochemical properties of the as-synthesized samples are examined using X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller measurements, scanning electron microscopy, high resolution transmission electron microscopy and energy dispersive X-ray spectroscopy measurements. Used as working electrodes for supercapacitors, MoSe2 nanostructures could deliver the specific capacitance of 106 F g−1 at 2 mV s−1 scan rate. Further, doping with tungsten (W) demonstrates the variation of specific capacitances with 2 M % of tungsten as the optimum doping amount, delivering the maximum specific capacitance of 147 F g−1. Furthermore, graphene composites of these nanostructures deliver the enhanced specific capacitances of 248 F g−1 and complimented with excellent capacitance retention capability of 102% for 20000 cycles.