Understanding pore size relation in cellulose-derived, nitrogen-doped, hydrothermal carbons for improved supercapacitor performance

Abstract

This study introduces an eco-friendly approach for synthesising cellulose-derived activated carbons, using hydrothermal carbonisation (HTC) followed by high-temperature pyrolysis. This novel method proves more carbon-efficient than the traditional carbonisation and activation processes. Moreover, we incorporate albumin as a sustainable nitrogen source in the preparation phase, with a view to enhancing the properties of the resulting carbons. We examine the morphological and textural characteristics of the carbons produced using scanning electron microscopy (SEM) and nitrogen sorption analysis. The chemical structure of the activated carbons was characterised using elemental microanalysis, Energy-Dispersive X-ray Spectroscopy (EDX), and X-ray Photoelectron Spectroscopy (XPS). The electrochemical evaluation was conducted in a symmetrical Swagelok cell, with a 2 M H₂SO₄ aqueous solution electrolyte. The carbons obtained exhibited remarkable electrochemical performance, achieving capacitance values exceeding 275 F g⁻¹ and power densities approaching 3000 W kg⁻¹. Crucially, we discovered a significant correlation between enhanced material capacitance and the presence of pores of around 4.3 Å, the approximate diameter of the sulfate ion (SO₄²⁻). This work highlights the significance of specific pore size in the electrochemical behaviour of the electrodes, advancing our understanding of the relationship between material structure and performance, and provides insight for the further development of sustainable high-performance materials for energy storage applications.