Supercapacitor-Type Behavior of Carbon Composite and Replica Obtained from Hybrid Layered Double Hydroxide Active Container

摘要

An original concept based on carbon replica method and adapted on organic/inorganic (O/I) hybrid layered double hydroxide (LDH) assembly is used to impart resulting carbon composites and replicas with interesting electrochemical properties. Thanks to the isomorphous cation substitution possible within the LDH layers, a series of O/I materials are prepared using the emulsifier 2-acrylamido-2-methyl-1-propanesulfonate acid (AMPS) as a source of carbon and Zn2Al, Co2Al_(0.5)Fe_(0.5) and Ni2Al as the LDH framework container. The process of carbonization and acid leaching is characterized by in situ X-ray diffractometry, Raman spectroscopy, and the pore formation of the resulting carbon replica by nitrogen adsorption. According to the carbonization/ acid-leaching procedure, the electrochemical behavior is characterized in various aqueous electrolytes, using four salts, including 1.0 M NaNO3, 0.5 M Na2SO4, 1 M Na2SO3, and 6 M KOH by means of cyclic voltammetry, galvanostatic mode, and complex impedance spectroscopy. Here, the key facet is the combination of the capacitive behavior of carbon, the pseudo-capacitive response coming from its functionalized surface, as well as redox reactions resulting from the inorganic particles present in the carbon composite and acting as a pore former during the acid leaching. From an optimized potential window of 1.2 V in 1 M Na2SO3, an electric energy of 11.0 W h/kg associated with a power density of 87.75 kW/kg is retrieved at a current density of 10 mA/g for carbon replica obtained from Co2Al_(0.5)Fe_(0.5)/AMPS, and this is determined to be stable at moderate regime without significant capacitance fading. Meanwhile, a corresponding carbon composite, i.e., before acid leaching, presents over an optimized potential window of 1.8 V, a capacitance per surface unit of 92.6 μF/cm~2 at slow scan rate, largely because of the pseudo-capacitance effect, and a reversible redox reaction of 43 mAh/g is obtained at the C/3 regime in galvanostatic mode. Finally, preliminary tests in an asymmetric capacitor give some hints on the versatility of the new innovative approach using electrochemically active template, which creates the carbon part with suitable (pseudo)-capacitive properties, as well as being electronically conductive embedding inorganic redox centers.