# CoNiO2/Co3O4 Nanosheets on Boron Doped Diamond for Supercapacitor Electrodes

## TL;DR

Researchers developed a new supercapacitor electrode using CoNiO2/Co3O4 nanosheets on boron-doped diamond, achieving high capacitance and long cycle life.

## Contribution

A one-step electrodeposition method creates high-performance CoNiO2/Co3O4/BDD nanosheet electrodes for supercapacitors.

## Key findings

- The CoNiO2/Co3O4/BDD electrode shows a specific capacitance of 214 mF cm−2 and 85.9% capacitance retention after 10,000 cycles.
- The assembled asymmetric supercapacitor achieves 7.5 W h kg−1 energy density and 97.4% capacity retention after 10,000 cycles.
- The nanosheet structure improves ion diffusion and active material utilization, enhancing electrochemical performance.

## Abstract

Developing novel supercapacitor electrodes with high energy density and good cycle stability has aroused great interest. Herein, the vertically aligned CoNiO2/Co3O4 nanosheet arrays anchored on boron doped diamond (BDD) films are designed and fabricated by a simple one-step electrodeposition method. The CoNiO2/Co3O4/BDD electrode possesses a large specific capacitance (214 mF cm−2) and a long-term capacitance retention (85.9% after 10,000 cycles), which is attributed to the unique two-dimensional nanosheet architecture, high conductivity of CoNiO2/Co3O4 and the wide potential window of diamond. Nanosheet materials with an ultrathin thickness can decrease the diffusion length of ions, increase the contact area with electrolyte, as well as improve active material utilization, which leads to an enhanced electrochemical performance. Additionally, CoNiO2/Co3O4/BDD is fabricated as the positive electrode with activated carbon as the negative electrode, this assembled asymmetric supercapacitor exhibits an energy density of 7.5 W h kg−1 at a power density of 330.5 W kg−1 and capacity retention rate of 97.4% after 10,000 cycles in 6 M KOH. This work would provide insights into the design of advanced electrode materials for high-performance supercapacitors.