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A facile approach of in situ electrochemical oxidation has been utilized to modify carbons, including activated carbon, mesoporous few-layer carbon, graphite, carbon fiber, and carbon nanotube, which induces oxygen-containing functional groups on its surface and simultaneously enhances its wettability, contributing to the improvement of capacitance. By this approach, the capacitance of commercialized activated carbon is increased by 86% in an acidic electrolyte, reaching 320 F g–1, of which more than 96% was maintained after 10 000 cyclic tests. The huge improvement stems from electrochemical redox reactions enabled by oxygen-associated groups, which do not adversely affect the porous structure and electrical conductivity. Such improvement will put carbon-based electrochemical capacitors into more practical application areas.

Highly capacitive carbons are viewed as promising commercial materials for supercapacitors, but few species satisfy the requirements of high capacitance and low cost. Here, we demonstrate an extraordinary porous few-layer carbon by facile Pechini combustion of magnesium nitrate gel, which combined salicylic acid as a complexing agent with magnesium nitrate as an inorganic metal salt. The as-synthesized carbon material delivers a capacitance of 415 F g–1, mostly stemming from a large specific surface area (∼1312 m2g–1), a fluent channel for transport of the electrolyte, as well as electrochemical redox reactions at O,N-associated active sites. Such porous few-layer carbons may accelerate the adoption of carbon-based supercapacitors for commercial high-power energy storage applications.