Fe catalysed transformation of oxygen functional groups on coal based needle coke for sodium storage.

The oxygen functional groups (OFGs) on the surface of carbon materials are regarded to be efficient and stable sodium storage sites. Herein, we selected coal-based needle coke (NC) with industrial prospects as raw materials. The C–O contained OFGs without sodium storage activity were transformed to the C=O contained OFGs with sodium storage activity by Fe catalysed transformation. Moreover, the ring graphite domains were induced during the catalytic reaction. Based on the above, a balance state between abundant sodium storage sites and suitable electron distribution was formed on the surface of NC. Therefore, the modified NC showed the reversible capacities of 306 mA h g−1 at 0.05 A g−1 after 100 cycles and 194 mA h g−1 at 2 A g−1 after 1000 cycles. Moreover, reversible potassium storage capacities of 327 mA h g−1 at 0.03 A g−1 after 50 cycles and 99 mA h g−1 at 1 A g−1 after 1000 cycles could also be achieved for the sample. The work provides a reasonable and convenient path to realize the balance between electrochemical active sites and electronic conductivity, and gives a reference for directional oxygen functionalization of carbon materials in the field of energy storage. Directional transformation from C–O contained groups to C=O contained groups was achieved by Fe catalysed reaction on coal based needle coke, leading to enhanced Na/K storage performance. [Display omitted] [ABSTRACT FROM AUTHOR]