Facile Synthesis of Templated Activated Carbon from Cellulose Nanofibers and MgO Nanoparticles via Integrated Carbonization-activation Method as an Eco-friendly Supercapacitor (Supporting Information)

A green, rapid, and facile synthesis method of activated carbon was developed and optimized using 50 nm MgO nanoparticle (NP)-based pore templating in tandem with an integrated drying and carbonization-activation heat treatment. TEMPO-oxidized cellulose nanofibers (TOCN) were mixed with MgO NPs and KOH, freeze-dried, heat treated first at 350 °C then at 800 °C to get templated activated carbon. Selective pore formation by MgO and KOH resulting in the development of mesopores and micropores, respectively was confirmed. NP-based templating is confirmed to be viable even with continuous heat treatment, and does not affect any transformations during each heat treatment phase. Through optimization for the highest surface area and optimal hierarchical porosity, templated activated carbon had a high specific capacitance of 269 F g⁻¹ at 0.5 A g⁻¹ with 95.92 % cycle stability after 2000 charge-discharge cycles at 10 A g⁻¹.