Improved electro-grafting of nitropyrene onto onion-like carbon via in situ electrochemical reduction and polymerization: tailoring redox energy density of the supercapacitor positive electrode

Abstract

International audienceHerein, we report a improved method for the physical grafting of 1-nitropyrene (Pyr-NO2) onto highly graphitized carbon onion. This is achieved through a lowering of the onset potential of the pyrene polymerization via in situ reduction of the NO2 group. The additional redox activity pertaining to the reduced NO2 enables exceeding the faradaic capacity which is associated with the p-doping of the grafted pyrene backbone, as observed for pyrene, 1-aminopyrene, and unreduced Pyr-NO2. Theoretical calculations demonstrate the charge transfer and binding enthalpy capabilities of Pyr-NO2, which are significantly higher than those of the other two species, and which allow for improved p-stacking on the carbon surface. Upon 20 wt % grafting of Pyr-NO2, the capacity of the electrode jumps from 20 mAh g-1 electrode to 38 mAh g-1 electrode, which corresponds to 110 mAh g-1 per mass of Pyr-NO2 and the average potential is increased by 200 mV. Very interestingly, this high performance is also coupled with outstanding retention with respect to both the initial capacity for more than 4000 cycles, as well as the power characteristics, demonstrating the considerable advantages of employing the present in situ grafting technique

Experimental and Theoretical Study of the Effect of Functionalized Pyrene Polymerization on Carbon Electrode Surfaces for Electrochemical Storage

“…On the other hand, C ad Pyr and C ad PAc show slightly lower capacities of 17 mAh/g. The advantage of such low‐levels of functionalization is they will not hamper the power characteristics of the resulting MWCNT/polymer composites as shown previously, [21] however the capacities remain too low for practical applications. One strategy to enhance the functionalization yield is in‐situ electropolymerization, by dissolving the monomers directly in the electrolyte of the battery, [21,22] (Protocol 2, see experimental section).…”

“…The advantage of such low‐levels of functionalization is they will not hamper the power characteristics of the resulting MWCNT/polymer composites as shown previously, [21] however the capacities remain too low for practical applications. One strategy to enhance the functionalization yield is in‐situ electropolymerization, by dissolving the monomers directly in the electrolyte of the battery, [21,22] (Protocol 2, see experimental section). However, this requires many cycles, [21,22] before the maximum capacity can be reached, as seen in Figure S14 for the PPrAc/MWCNT system which requires 200 cycles before doubling the initial capacity of the MWCNT electrode.…”

“…One strategy to enhance the functionalization yield is in‐situ electropolymerization, by dissolving the monomers directly in the electrolyte of the battery, [21,22] (Protocol 2, see experimental section). However, this requires many cycles, [21,22] before the maximum capacity can be reached, as seen in Figure S14 for the PPrAc/MWCNT system which requires 200 cycles before doubling the initial capacity of the MWCNT electrode.…”

“…Waltman and Bargon [18] extensively studied the electropolymerization of polycyclic hydrocarbon molecules at the surface of metal electrodes suggesting their possible application for energy storage, as they show very stable capacity during cycling. Several PAHs have been proposed for this purpose such as pyrene, indole and carbazole derivatives, [18–20] Our group has shown the pyrene family displays excellent cycle life even at high positive potential, [12,21,22] while electron‐withdrawing substituents attached to pyrene enhance π‐stacking type interactions with graphitic carbon , [21,22] . Lee et al [12] .…”

Pre‐Lithiation Strategies for Lithium Ion Capacitors: Past, Present, and Future

“…The main advantage of this approach is that the redox potential of the monomer can be tuned between 3.5 and 4.5 V vs. Li + /Li, depending on the nature of the utilized pyrene substituents. [62][63][64] It was also shown that the Li + source does not need to be an electron conductor, hence, a low-cost, airstable and a non-soluble inorganic base, Li 3 PO 4 , which plays a key role on scavenging the protons released by pyrene, was proposed. Thus, the combination of pyrene and Li 3 PO 4 together with the AC in the positive electrode successfully pre-lithiated a carbon black based LIC.…”