Influence of Precursor Composition on Microstructure Formation in Protein-Derived Porous Graphitic Aerogels

Hierarchically porous graphitic aerogels (HGAs) are promising carbon materials owing to their low density, multilevel porosity, and interconnected frameworks, making them suitable for applications in energy storage, water purification, and environmental remediation. In this work, HGAs were synthesized from a range of protein-based precursors, including pasteurized egg white (PEW), α-lactalbumin, β-lactoglobulin, bovine serum albumin (BSA), and yogurt, through pyrolysis. The study investigates how precursor composition influences thermal decomposition and microstructural development. All precursors except yogurt formed interconnected sheet- and fiber-like frameworks due to the self-foaming effect during pyrolysis. Despite its high protein content, the yogurt precursor produced a rough porous morphology, likely due to the presence of fats and inorganic species that inhibit foaming action. Elemental analysis confirmed the presence of significant amounts of inorganic species, such as calcium and phosphorus, in the yogurt-derived samples. To examine the influence of nonprotein constituents, a control experiment was conducted using a casein-whey mixture, the primary protein component of yogurt. Pyrolysis of this mixture produced aerogels with interconnected sheet- and fiber-like morphologies, confirming that the additional nonprotein components in yogurt affect structure formation. Further Raman analysis indicates that increasing the pyrolysis temperature enhanced carbonization and graphitic ordering across all the samples. Overall, this work provides insight into developing HGAs from diverse protein precursors and shows how precursor composition influences microstructural development during protein pyrolysis, offering valuable guidance for the design of HGA-based composites and functional materials.