Interfacial, solvent-free room-temperature adsorption of quinone derivatives on activated carbon for sustainable energy storage electrodes

Abstract

Redox-active quinone derivatives (QDs) were hybridized with activated carbon (AC) through a solvent-free, room-temperature process that requires only mixing the two components in a sealed container. Four represetative QDs—tetramethyl-1,4-benzoquinone (TMBQ), 2,6-di-tert-butyl-1,4-benzoquinone (DBBQ), phenylbenzoquinone (PBQ), and naphthoquinone (NQ)—were exmamined. TMBQ, DBBQ, and NQ were rapidly adsorbed via interfacial interactions from AC particle surfaces into the pores, whereas PBQ exhibited relatively slower adsorption. Importantly, water molecules inherently present in AC pores did not hinder QD adsorption, demonstrating that drying is unnecessary. By quantifying the water content in AC, adsorption levels can be precisely controlled without the need for heating or vacuum treatment. Structural and calorimeric analyses confirmed that adsorption was driven by strong π-π interactions. When evaluated in an aqueous H₂SO₄ electrolyte, the AC/QD hybrids showed extensive interfacial contact between QDs and conductive carbon surfaces, facilitating rapid and reversible redox reactions confined within the AC pores. As a result, the hybrids delivered significantly enhanced volumetric capacitances compared with pristine AC and maintained higher absolute volumetric capacitance even after 10 000 cycles, when employed as electrochemical capacitor electrodes. This interfacial adsorption strategy eliminates the need for organic solvents, heating, vacuum treatment, filtration, drying, purification, and specialized apparatus, underscoring the decisive role of interfaces in governing electrochemical behavior. The findings demonstrate a sustainable and energy-efficient pathway to high-performance carbon-quinone hybrid electrodes, advancing interfacial science in electrochemical energy storage.