Dielectric relaxation and polaron hopping in biomass derived activated carbon

Abstract

Activated carbon samples were obtained by alkali (KOH) activation and subsequent carbonisation of an identified biomass precursor at 600 °C, 800 °C, 1000 °C, and 1200 °C temperatures, in nitrogen atmosphere. Dielectric property changes with respect to the change in microstructure in the activated carbon samples was studied. High dielectric constant values at low-frequency regions (<10³ Hz) were observed in all samples, due to trapped K⁺ ions, polar groups (C = C, C = O, –NH₂, –OH), and interfacial polarisation. The trapped K⁺ ions also contributed to high dielectric dispersion at low-frequency regions. Carbonisation at 600 °C resulted in amorphous carbon formation with some intact cellulose crystallites. Thermal de-trapping of K⁺ ions resulted in an increase in dielectric constant with frequency up to 10³ Hz. Carbonisation at 800 °C and 1000 °C resulted in nanocrystalline graphene oxide (GO), with interfacial polarisations dominant in charge storing and in the relaxation processes. Carbonisation at 1200 °C resulted in a carbon nanotube (CNT) network and negative dielectric constant values at 70 °C was observed due to the Surface Plasmon Resonance effects of the formed CNT. With increase in carbonisation temperature, a change in Debye-type to non-Debye-type relaxation process was observed, supported by the Dielectric formalism studies and the Cole–Cole plot.

Keywords:

• Biomass derived carbon
• dielectric properties
• ionic
• polar and interfacial polarisation
• polaron hopping
• plasma oscillation

Acknowledgements

The authors are thankful to Central Research Facility (CRF), KIIT, Bhubaneswar for providing the characterisation facilities.

Author contributions

Dhani Soren—Methodology, Data acquisition and Curation, Formal analysis, Writing

Gayatree Mehena—Data acquisition and Curation, Formal analysis, Writing

Puspalata Pattojoshi—Conceptualisation, Supervision

Pratap Kumar Deheri—Conceptualisation, Validation, Review and Editing

Conflicts of interest

The authors declared that there is no conflict of interest.

Data and code availability

Data available within the article.