This
report anticipates a thorough strategy for the utilization
of high entropy oxide (HEO) nanoparticles (1) as a cost-effective
catalyst for the growth of high yield carbon nanotubes (CNTs), resulting
in HEO–CNT nanocomposites, and (2) the implementation of HEO–CNT
nanocomposites for energy applications such as electrochemical capacitors
(ECs). In the first step, HEO nanoparticles were synthesized by a
simple sol–gel autocombustion method and then the as-synthesized
HEO nanoparticles were ground and used as the catalyst for the growth
of CNTs by chemical vapor deposition technique. The as-grown CNTs
(HEO–CNT nanocomposite) exhibited unexpectedly high yield,
a superior specific surface area of ∼151 m2 g–1, and encapsulation and diffusion of the catalyst
throughout the HEO–CNT nanocomposite, providing remarkably
high mechanical strength, which make them a promising candidate for
energy applications. To study the electrochemical activity of the
HEO–CNT nanocomposite, half-cell and full-cell ECs were assembled
in different electrolytes. Stupendously, a complete 100% capacitance
retention and a Coulombic efficiency up to 15 000 cycles were
realized for the HEO–CNT nanocomposite-based full-cell EC assembled
in the polyvinyl alcohol/H2SO4 hydrogel electrolyte.
Additionally, a high specific capacitance value of 286.0 F g–1 at a scan rate of 10 mV s–1 for the HEO–CNT
nanocomposite-based full-cell EC assembled in the [BMIM][TFSI] electrolyte
with a wide potential window of 2.5 V is reported. Also, high energy
density and power density of ∼217 W h kg–1 and ∼24 521 W kg–1, respectively,
are reported. Furthermore, the HEO–CNT nanocomposite-based
full-cell EC assembled in the [BMIM][TFSI] electrolyte can successfully
light up a red light-emitting diode, demonstrating great potential
of the HEO–CNT nanocomposite in the various energy applications.