Multi-carbonyl molecules immobilized on high surface area carbon by diazonium chemistry for energy storage applications

The diamino-aryl-1,4,5,8-naphtalenetetra-carboxylic diimide molecule (NTCDA-(aryl-NH₂)₂) was successfully prepared by N-acylation reaction of 1,4,5,8-naphtalenetetra-carboxylic dianhydride (NTCDA) with 4-nitroaniline, followed by a simple reduction of nitro groups in amino functions. The molecules were characterized by elemental analysis, SEM, IR and TGA. A Li-ion electrode with NTCDA-(aryl-NH₂)₂ as active material was tested and a reversible behavior was observed with a multiple electrons process delivering about 100 mAh g⁻¹ at an average potential of 2.45 V vs. Li/Li⁺. The diazotization of NTCDA-(aryl-NH₂)₂ and its attachment on a carbon surface was investigated. An irreversible cathodic wave at around 0.0 V vs. Ag/AgNO₃ that is associated to the reduction of the in-situ generated NTCDA-(aryl-N₂⁺)₂ ions was observed. The blocking effect of the grafted layer deposited on the glassy carbon surface was verified with ferrocene as a redox probe. This molecule was further immobilized on Ketjen black carbon in a one-pot reaction by spontaneous reduction of freshly formed NTCDA-(aryl-N₂⁺)₂ ions. The redox-active carbons with a loading of grafted groups estimated between 26.4 and 36.7 wt % cycled at high rate for thousands of cycles. Two other diamines prepared according to the same method were also investigated, as well as their immobilization on Ketjen black surface.