High Entropy Oxides-A Cost-Effective Catalyst for the Growth of High Yield Carbon Nanotubes and Their Energy Applications

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 assynthesized 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 similar to 151 m(2) 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] [TFST] electrolyte with a wide potential window of 2.5 V is reported. Also, high energy density and power density of similar to 217 W h kg(-1) and similar to 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.