Dual-role of ZnO as a templating and activating agent to derive porous carbon from polyvinylidene chloride (PVDC) resin

Activated carbon, with its porous morphology and extremely high surface area, maintains the exclusive position as an electrode material in supercapacitors owing to its low manufacturing cost. Although its surface area can be boosted using a chemical etchant to create nanoscale pores, the use of chemicals requires a post-washing of the material to eliminate impurities. Herein, the activation of polyvinylidene chloride (PVDC) resin using ZnO chemical is described to prepare porous activated carbon materials for use as supercapacitor electrodes. During heat-treatment of a 1:1 mass ratio of PVDC resin:ZnO at 950 °C, activation and templating processes consecutively take place to produce porous carbon. Between 140 °C and 600 °C, ZnCl₂ formed from the conversion of ZnO chemically activates the carbon with creating micropores. Above 800 °C, unreacted ZnO from the initial activation is reduced to Zn upon oxidation of the carbon with the additional micropore creation. Above 907 °C the Zn evaporates to leave activated carbon with no impurities. Through this process, the sites initially occupied by ZnO would turn to the pores by templating. With a rationally-designed ZnO ratio, porous carbon can be produced without washing. The activated carbon exhibits a high quinone content that reacts with H⁺ ions, with a high specific capacitance of 219 F g⁻¹ in 1 M H₂SO₄ based on pseudocapacitance. However, the rate performance of this material is 55% due to the slow kinetics of the charge transfer reaction. On the contrary, a high quaternary-N content increases the rate capability of the material in 6 M KOH, where the double-layer mostly contributes toward charge storage.