Vertically aligned boron-doped diamond nanostructures as highly efficient electrodes for electrochemical supercapacitors

Abstract

Nanostructured boron-doped diamond (BDD) offers a sizeable ion-accessible area, high mechanical robustness, and high electrical conductivity, and could be a suitable electrode for high-performance electrochemical (EC) supercapacitors. Herein, two morphological BDD films, namely, boron-doped microcrystalline diamond (BMCD) and boron-doped ultra-nanocrystalline diamond (BUNCD), are employed for nanostructuring. The diamond nanopillars are fabricated via the Au mask-assisted reactive ion etching (RIE) method. The nanostructured samples of BMCD and BUNCD are termed BMCD_N and BUNCD_N. The Raman spectroscopy and X-ray photoelectron spectroscopy measurements of these nanostructured samples confirm the presence of sp² in sp³-bonded carbon, which combine to offer good EC activity of sp² and exceptional stability of sp³ carbon. These nanostructured BDD samples with enhanced surface area are utilized as electrode materials to construct an electric double-layer capacitor and pseudocapacitor. In 1 M Na₂SO₄ solution, the maximum specific capacitance of BMCD_N is found to be 0.0852 mF cm⁻², whereas, for BUNCD_N the value is 0.0784 mF cm⁻². The electrochemical analysis of these samples shows they exhibit superior electron transfer kinetics with 80% capacitance retention after 2000 cycles, which indicates the suitable utilization of these nanostructured samples as electrodes in EC supercapacitors.