Electrospray of Precursor Sol on Carbon Paper and in Situ Carbonization for Making Supercapacitor Electrodes

Abstract

This paper describes the electrospray of resorcinol−formaldehyde (RF) sol on a carbon paper for making carbon electrodes. The sol layer undergoes curing, solvent removal, and pyrolysis under an inert atmosphere. In a separate study, the powdered carbon samples were derived from bulk RF-gel samples, prepared in bottles. The gel composition and the processing method were systematically varied. The EDX and BET analyses of the carbon samples helped in arriving at an optimized composition of the precursor sol, and the processing method for the electrospray derived carbon film. The electrodes showed a specific capacitance of 200 F g −1 at 0.1 A g −1 of current density with 2 M potassium chloride solution as electrolyte. The high value of specific capacitance was possible by the splitting of precursor sol prior to deposition on the current collector, and also by removal of solvent by lyophilization that retained the pore structure of the gel.

Revisiting the Effect of Pyrolysis Temperature and Type of Activation on the Performance of Carbon Electrodes in an Electrochemical Capacitor

“…In this article, the composition of the RF solution, as stated in the previous section, was taken from a previous study based on a high surface area with a significant proportion of mesopores [ 11 , 12 ]. For this purpose, the cross-link density in the polymeric gel was controlled through a variation of the R/C and R/D molar ratios.…”

“…The tailoring of micro-mesoporous structure in RF-based carbon electrodes for EC applications is mostly investigated through synthesis steps by optimising concentrations of monomer, catalyst, and diluents, etc. [ 11 , 12 ], controlling the sol-gel transition period [ 11 ], or maintaining the pH of the initial precursor sol [ 11 , 12 ], drying protocols [ 7 , 13 , 14 ], solvent exchange steps [ 12 ], and activation protocols [ 7 , 15 , 16 ]. However, there is not much investigation in the prior art on the carbonisation stage that shows how the porous texture with pore connectivity, surface functionality, electrical conductivity, or degree of amorphous/crystalline nature arises at different carbonisation temperatures and their resulting performances when used as electrodes for ECs.…”

Growth of Film Electrodes through Electrospray Coating of Precursor Sol for Use in Asymmetric Supercapacitor

“…The rate of reaction depends on the concentrations of reactants, catalyst, and diluent, which, in turn, influence the cross-link density and finally, the pore structure of the carbonized film. The “gel-time” is a manifestation of the reaction rate and can be stretched by optimizing the sol composition and catalyst concentration, to arrive at the desired pore structure in the final product. , The other control of pore size was possible through avoiding the use of vacuum for removal of solvent such that no significant collapse of the void space occurs due to vapor–liquid interfacial stresses Figure shows the SEM image of the carbon film at two different magnifications.…”

“…The carbon electrodes were prepared by electrospray deposition of resorcinol–formaldehyde (RF) sol on Ni foam, followed by in situ curing, solvent removal, and carbonization. Here, the polymeric precursor of carbon consisted of resorcinol (R, recrystallized extra pure), formaldehyde (F, 37-41% w/v GR; stabilized by 8–14% methanol), sodium carbonate (C, anhydrous) as a catalyst, and deionized water (D) as diluents in accordance with the following molar ratios: R/F = 0.5, R/C = 300, and R/D = 0.018. All of these chemicals were obtained from Merck specialities, India.…”

“…Also, the process does not require any stringent conditions, e.g., a high level of vacuum. The electrospray process is widely studied for surface coating purposes and producing thin films of metal oxides and chalcogenides, , hollow nanospheres of inorganic, organic, and hybrid materials, and nanospheres and films of carbon. − …”