Hydrothermal synthesis and electrochemical properties of Sn-based peanut shell biochar electrode materials

Abstract

Using activated-carbon-based electrodes derived from waste biomass in super-capacitor energy technologies is an essential future strategy to achieve sustainable energy and environmental protection. Biomass feed-stocks such as bamboo and straw have been used to prepare activated carbon-based electrodes. This experiment used peanut shells (waste biomass) as carbon precursors. Peanut shell-activated biochar materials were prepared using KOH activation and heat treatment, and SnO₂@KBC-CNTs, a composite electrode material of biochar loaded with tin oxide. It was produced through hydrothermal synthesis, utilizing SnCl₄–5H₂O as the tin precursor. The application of KOH activators during pyrolysis markedly enhanced the porosity and specific surface area of the resultant activated biochar, due to effective dispersion and degradation of pyrolytic products. Characterized by a micro–mesoporous structure, the composite's pores boasted a specific surface area of 158.69 m² g⁻¹. When tested at a density of current of 0.5 A g⁻¹, the specific capacitance of SnO₂@KBC-CNTs reached 198.62 F g⁻¹, nearly doubling the performance of the KBC electrode material alone. Moreover, the composite demonstrated a low ion transfer resistance of 0.71 Ω during charge–discharge cycles.