One-Pot Synthesis of Biomass-Based Hierarchical Porous Carbons with a Large Porosity Development

A sustainable one-pot scheme for the synthesis of hierarchical porous carbons formed from biomass is developed herein. It is based on the carbonization of biomass-derived products (glucose, glucosamine, soya flour, and microalgae) in the presence of an activating agent (potassium oxalate) and calcium carbonate nanoparticles that form a hard template. During carbonization, double carbonates are formed in situ, which results in modifications in the morphology and size of the template nanoparticles, giving rise to a carbon material with an open macroporous foam-like structure rich in micro-/mesopores, the latter developing via a redox reaction between the carbon and potassium carbonate and also as a result of the reaction between the carbon and the evolved CO2. The porosity can be tailored by selecting an appropriate precursor. Thus, the carbon materials are basically micro-/macroporous in the case of glucose and glucosamine, and micro-/meso-/macroporous when soya flour and microalgae are used. A direct relationship is observed between the amount of nitrogen present in the precursor and mesopore development. Hence, the addition of urea to the mixture of glucose and potassium oxalate and CaCO3 nanoparticles also yields micro-/meso-/macroporous carbons. The materials synthesized at 800 °C have large surface areas in the ∼1800–3100 m2/g range. At 750 °C, the materials synthesized from N-rich biomass combine ultralarge surface areas of 2400–3050 m2/g and a remarkable N-doping (2–3 wt % N). This combination of textural and chemical properties is highly appealing for many energy-related applications and also for adsorption-based processes.