Cyano groups: New active sites of porous carbon materials achieving a superior K-ion storage

Abstract N-doping can endow carbon materials with high electrochemical activity. Besides the widely validated sp2-hybridized nitrogen doping, sp-hybridized nitrogen (sp-N) atoms are also expected to be new active sites. However, both sp-N atoms and cyano (CN) groups containing sp-N are rarely produced in carbon materials presently. In this work, the first cyano groups-modified carbon materials are synthesized firstly via an interesting struggle between the chemical etching of KOH and the catalytic graphitization of Co nanoparticles in carbon frameworks. The theoretical calculations and experimental results manifest that the stronger electronegativity of CN groups renders carbon materials a higher electrochemical activity. As K+ storage anodes, the CN−modified carbon materials exhibit an obvious boost in potassium storage performance in both ester- and ether-based electrolytes. Therefore, as a new N doping form, the successful introduction of CN groups into carbon materials opens a door for exploring sp-N doped carbon materials for applications in energy storage and other fields.