Influence of external carbon sources on the morpho-structural and mechanical properties of 3D-structured carbon monoliths

Abstract

High purity carbon structured devices have been prepared by resorcinol-formaldehyde polycondensation in aqueous medium and alkaline conditions with starch as a binder and various external carbon sources. Polylactic acid (PLA) templates have been used to perform the structures which, after controlled and fixed pyrolysis conditions, generate 3D carbon devices with tuneable geometry and properties, as well as mechanical integrity. This study investigates the influence of the nature of the added carbon (activated charcoal, powdered graphite, multi-walled carbon nanotubes, cellulose-derived biocarbon, and synthetic carbon xerogel) on the morpho-structural and mechanical properties of the resulting monoliths. The nature and proportion of the added carbon significantly affect crystallinity, porosity, surface area, and compressive strength. The addition of either carbon xerogel or carbon obtained by pyrolysis of cellulose allows obtaining structures with channels with suitable mechanical properties with no volume reduction or structural collapse. The best mechanical properties are obtained using carbon xerogel as additive, as it allows using a higher C/OS weight ratio (1.61), giving an apparent density of 0.79 g/cm3 and compressive strength (σ) of 5.4 MPa. The use of sustainable cellulose-derived carbon as additive results in a monolith with lower mechanical properties (apparent density = 0.46 g/cm3, σ = 1.4 MPa), probably due to the lower C/OS ratio (0.42) but higher mesoporosity (42 vs. 17 %), emerging as the most promising candidate for structured catalytic support applications. The methodology enables the fabrication of high-purity carbon structures with customizable properties suitable for advanced catalytic processes.Financial support was obtained from Spanish Ministerio de Ciencia e Innovación (MCIN/AEI /10.13039/501100011033/) and for FEDER Funds (Una manera de hacer Europa), Project PID2020-113809RB-C32.Peer reviewe