Enhancement of the electrochemical properties of commercial coconut shell-based activated carbon by H ₂ O dielectric barrier discharge plasma

Abstract

Commercial coconut shell-based activated carbon (CSAC) has low specific capacitance and specific capacitance retention owing to its undeveloped pore structure and low proportion of heteroatoms. In this study, dielectric barrier discharge plasma was used to enhance the specific capacitance and rate capability of CSAC. H 2 O was used as an excited medium to introduce oxygen functional groups. The physico-chemical properties of CSAC and CSAC modified by H 2 O plasma (HCSAC) were revealed by automated surface area and pore size analysis, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. Electrochemical work was applied to investigate the electrochemical properties of CSAC and HCSAC. The results obtained showed that plasma modification improved the specific capacitance of CSAC by 64.8% (current density, 1 A g −1 ; electrolyte, 6 M KOH solution) within 100 s. This result is ascribed to the oxygen functional groups introduced to the surface of CSAC. It can also improve the hydrophilicity and wettability of the carbon surface leading to an increase from 76.7% to 84.6% in specific capacitance retention. Furthermore, H 2 O plasma modification can introduce oxygen functional groups without destroying the initial pore structures of CSAC. In summary, we provide a simple, fast, environment-friendly modification method to enhance the electrochemical properties of CSAC.

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“…In Fig. 3(a, c, e), the decomposition of C1s spectra of all activated samples show three peaks at 284.8 eV, 286.3 eV, and 288.4 eV, which are attributed to the C─C, C─O/-C═O, and COOgroups, respectively [72,73]. The resolution of O 1 s can be also deconvolved into three peaks, as shown in Fig.…”

“…3(b, d, f). They reflect oxygen groups in carbonyl C═O and/or quinone (531 ± 0.2 eV), hydroxyl (C─OH) and/or ether (C─O─C) (532.4 ± 0.3 eV) and carbonyl (COO -) (533.5 ± 0.3 eV) [73,74]. Chemical composition and functional groups determined by XPS are summarized in Fig.…”

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