Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

A full understanding of ion transport in porous carbon electrodes is essential for achieving effective energy storage in their applications as electrochemical supercapacitors. It is generally accepted that pores in the size range below 0.5 nm are inaccessible to electrolyte ions and lower the capacitance of carbon materials. Here, nitrogen‐doped carbon with ultra‐micropores smaller than 0.4 nm with a narrow size distribution, which represents the first example of electrode materials made entirely from ultra‐microporous carbon, is prepared. An in situ electrochemical quartz crystal microbalance technique to study the effects of the ultra‐micropores on charge storage in supercapacitors is used. It is found that ultra‐micropores smaller than 0.4 nm are accessible to small electrolyte ions, and the area capacitance of obtained sample reaches the ultrahigh value of 330 µF cm−2, significantly higher than that of previously reported carbon‐based materials. The findings provide a better understanding of the correlation between ultra‐micropore structure and capacitance and open new avenues for design and development of carbon materials for the next generation of high energy density supercapacitors. A special structure of material with unimodal 0.3–0.4 nm nanopores is successfully synthesized, by a simple low‐temperature solvothermal route, and using in situ electrochemical quartz crystal microbalance measurements to directly reveal the effects of the ultra‐micropores (i.e., pores smaller than 0.4 nm) on charge storage in supercapacitors. This is the first example of a supercapacitor made from a unimodal ultra‐microporous carbon electrode material.