Removing Cost Barriers to Template Carbon Synthesis for High-Performance Supercapacitors by Establishing a Zero-Emission Chemical Cycle from CO2

Template carbon (TC) is one of the most promising electrode materials for clean-energy devices (e.g., supercapacitors), but its application is hampered by the high cost of templates and carbon sources. Here, we report a green MgO template recycling technology that converts CO2 to high specific-surface-area TC by establishing a zero-emission chemical cycle at one-third the cost of nonrecycling methods. Up to 10 cycles of recycling demonstrate that the template's dissolution and regeneration, as well as TC's pore structure and physical properties, are extremely repeatable. Supercapacitors using symmetric TC electrodes deliver high-capacitance and -rate performances either in aqueous (KOH/H2O, >154 F g–1) or organic (Et4NBF4/AN, >140 F g–1) and ionic liquid (EMIMBF4, >178 F g–1) electrolytes, and ≈100% Coulomb efficiency, outperforming traditional commercial supercapacitors. This progress greatly reduces the cost of large-scale use of TC in supercapacitors and creates a sustainable link between CO2 reduction and clean-energy development.