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

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 BMCDN and BUNCDN. 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 BMCDN is found to be 0.0852 mF cm-2, whereas, for BUNCDN 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. Nanostructuring boron-doped diamond effectively improves the electrochemical supercapacitor performance with high lifetime stability.