Block‐Copolymer‐Assisted One‐Pot Synthesis of Ordered Mesoporous WO_3−<i>x</i>/Carbon Nanocomposites as High‐Rate‐Performance Electrodes for Pseudocapacitors

Abstract

Abstract An ordered mesoporous tungsten‐oxide/carbon (denoted as m‐WO 3− x ‐C‐s) nanocomposite is synthesized using a simple one‐pot method using polystyrene‐ block ‐poly(ethylene oxide) (PS‐ b ‐PEO) as a structure‐directing agent. The hydrophilic PEO block interacts with the carbon and tungsten precursors (resol polymer and WCl 6 ), and the PS block is converted to pores after heating at 700 °C under a nitrogen flow. The m‐WO 3− x ‐C‐s nanocomposite has a high Brunauer–Emmett–Teller (BET) surface area and hexagonally ordered pores. Because of its mesoporous structure and high intrinsic density of tungsten oxide, this material exhibits a high average volumetric capacitance and gravimetric capacitance as a pseudocapacitor electrode. In comparison with reduced mesoporous tungsten oxide (denoted as m‐WO 3− x ‐h), which is synthesized by a tedious hard template approach and further reduction in a H 2 /N 2 atmosphere, m‐WO 3− x ‐C‐s shows a high capacitance and enhanced rate performance, as confirmed by cyclic voltammetry, galvanostatic charge/discharge measurements, and electrochemical impedance spectroscopy. The good performance of m‐WO 3− x ‐C‐s is attributed to the high surface area arising from the mesoporous structure, the large interconnected mesopores, and the low internal resistance from the well‐dispersed reduced tungsten oxide and amorphous carbon composite structure. Here, the amorphous carbon acts as an electrical pathway for effective pseudocapacitor behavior of WO 3‐x .