Sustainable ZnCl2-activated cellulose-derived carbons enhanced with graphene as electrocatalysts in ORR

• Dry ZnCl 2 activation of microcrystalline cellulose (MCC) enabled a simple, scalable, and solvent-free route to porous carbons. • Specific surface area (SSA) increased systematically with activator loading, reaching exceptionally high values up to 2700 m 2 g −1 . • Hybrid composites with graphene nanoplatelets (GNPs) combined high conductivity with hierarchical porosity. • Enhanced oxygen reduction reaction (ORR) activity directly correlated with SSA and defect-rich active sites. • The proposed dual strategy offers a sustainable alternative to Pt-based catalysts for energy conversion devices. In this study, we report on the sustainable synthesis of novel electrocatalysts using ZnCl 2 -activated microcrystalline cellulose (MCC) as a renewable carbon precursor. Zinc chloride acts simultaneously as a chemical activator and dehydration agent, facilitating the formation of highly porous carbon structures with a large surface area (up to 2700 m 2 /g) and abundant defect sites or enhanced active centers, exhibiting high electrocatalytic activity in the oxygen reduction reaction (ORR). Furthermore, the addition of graphene nanoplatelets (GNPs) improved the conductivity and overall electrochemical activity of the synthesised materials, demonstrating their potential for energy storage applications such as metal-free electrocatalysts in fuel cells or metal-air batteries. This approach adds value to biomass waste and supports the development of green, low-cost alternatives to platinum-based catalysts, providing a promising pathway toward practical and sustainable energy conversion technologies