Hybrid Design Using Carbon Nanotubes Decorated with Mo2C and W2C Nanoparticles for Supercapacitors and Hydrogen Evolution Reactions

In view of recent environmental concerns, the need for energy security, and the ever-increasing demand for portable systems, the scientific community is strongly motivated to develop sustainable and renewable energy devices. Recently, the hydrogen evolution reaction (HER) and supercapacitors have become highly feasible technologies for supporting the global energy requirements. For this purpose, an efficient interface between carbon nanotubes (CNTs) decorated with metal carbide nanosheets (designated W2C@CNT and Mo2C@CNT) is developed herein via a facile one-pot methodology followed by carbonization. The hierarchical Mo2C@CNT nanostructures exhibit a symmetric capacitance of 367 F·g–1 at a current density of 1 A·g–1, and a high energy density of 50.9 W·h·kg–1 at a power density of 500 W·kg–1, along with an outstanding cycling stability with ∼97% capacity retention after 5000 cycles. In addition, both hybrids exhibit excellent HER performances in acidic and alkaline media, along with remarkable long-term stabilities for 24 h compared with pure CNTs. Thus, in an acidic medium, W2C@CNT and Mo2C@CNT exhibit small overpotentials of 155 and 121 mV and shallow Tafel slopes of 85 and 77 mV·dec–1. Similarly, in an alkaline medium, the respective overpotentials are 125 and 118 mV and the respective Tafel slopes are 104 and 92 mV·dec–1. The hierarchical structured W2C@CNT and Mo2C@CNT afford numerous pores or abundant active catalytic sites with large contact areas for the electrolyte and high conductivity, thus enabling superior electrochemical performance by facilitating the easy transfer of electrons or ions.