Holey carbon-nanotube-wrapped MXene for hydrogen evolution reactions and supercapacitor applications

Abstract

In recent years, interest in noble metal-free catalysts for the hydrogen evolution reaction (HERs) and supercapacitor (SCs) applications has emerging for altering the high-price of the catalyst and prohibiting the dissolution/phase change of the catalysts in long term performances. In this study, we present a novel noble metal-free electrocatalyst composed of holey carbon nanotubes (h-CNTs) and MXene nanocomposites for electrocatalytic HERs and SCs. By wrapping h-CNTs into the surface of the MXene sheet, we address the limitations of pure MXenes and achieve superior electrochemical performance. Specifically, MXenes containing 20 wt% h-CNTs exhibit a low overpotential of 192 mV versus RHE and a small Tafel slope of 48.95 mV dec−1 at 10 mA cm−2 in 0.5 M H2SO4 with excellent cyclic stability. The presence of CO functional groups and the existence of a holey in CNT probably enhanced the electrocatalytic activity. The excellent wrapping of h-CNTs on MXene efficiently exhibited the HER performances because of their individual effect and the arising of synergy, where the excellent interaction attained between the immobilized atom in the h-CNT and MXene. For SCs, MXenes containing 15 wt% h-CNTs display the highest specific capacitance of 404 F g−1 at 4 A/g with excellent cyclic stability, maintaining 80% capacity after 4000 cycles at 10 A/g at ambient temperature in 2 M KOH. Furthermore, the MXene@h-CNT nanocomposite was subjected to density functional theory (DFT) calculation. Our findings demonstrate that the newly developed nanocomposite offers a promising route to boost HER and SCs performance for a wide range of technological applications.