Fabrication of hydrophilic porous carbon from polyvinylidene chloride-resin via synergetic activation of ZnO and tetrahydrofuran for aqueous supercapacitors

For high capacitance, aqueous supercapacitors use large-area porous carbon electrode based on the charging principle of ion adsorption. Nonpolar hydrophobic carbon prevents ion adsorption, limiting the exploitation of porous surfaces. A carbon synthesis method was developed from pyrolysis of a polyvinylidene chloride-resin precursor and excess ZnO to derive a highly porous structure with a high surface area. Ion adsorption is limited by the small, newly formed pores. Added tetrahydrofuran expands the reaction region between the precursor and etchant during pyrolysis by dissolving the precursor. Moreover, tetrahydrofuran activates oxygen in the precursor and ZnO during pyrolysis, forming hydrophilic phenol and carboxylic acid. The hydrophilicity and pore expansion induced during pyrolysis convert the extra surface area into active charging sites. Hydrophilic carbon with enlarged pores increases the specific capacitance by 5.7 times to 126 F g⁻¹ (at 5 mV s⁻¹) and the rate capability by 2.7 times to 62% (50 mV s⁻¹ vs. 5 mV s⁻¹) in neutral K₂SO₄ solution compared to carbon made from polyvinylidene chloride-resin. Notably, the synthesized functional groups yielded a high capacitance of 243 F g⁻¹ based on the faradaic charging in the KOH electrolyte. Hydrophilic carbon originating from polyvinylidene chloride-resin can be a potential electrode with a high capacitance for aqueous supercapacitors.