Thin films from agroindustrial waste via liquid/liquid interfacial route: a proposal for sustainable energy storage materials

The current research develops sustainable carbonaceous materials from sugarcane bagasse for energy storage applications. Hydrothermal carbonization was employed, with and without iron (III) as an additive, followed by thermochemical activation. Comphehensive characterization was conducted to assess the physicochemical and magnetic properties of the carbonaceous materials, as well as the morphology and volumetric capacitance (Cv) of the thin films prepared via the liquid-liquid interfacial route (LLIR). The incorporation of iron (III) led to Fe₃O₄ and α-Fe nanoparticles formation within the carbonaceous matrix, though this encapsulation slightly hindered electrolyte accessibility after activation. Thermochemical activation enhanced the textural properties, thus impacting the Cv. The films, with an average thickness ranging from 10 to 189 nm, exhibited higher Cv values compared to those observed before activation. Additionality, films produced without iron achieved 442 F cm⁻³, surpassing the 83 F cm⁻³ obtained for those produced in the presence of iron. This discrepancy can be attributed to the challenge in electrolyte access to encapsulated nanoparticles within the carbonaceous matrix, resulting from the synthesis process. As a proof of concept, this study demonstrates the potential of LLIR for processing transparent thin film electrodes from biomass-derived carbonaceous materials, as well as a sustainable preparation methodology contributing to the development of future high-performance green energy storage devices.