Abstract
Cathodes for supercapacitors with enhanced capacitive performance are prepared using MnO2 as a charge storage material and carbon nanotubes (CNT) as conductive additives. The enhanced capacitive properties are linked to the beneficial effects of catecholate molecules, such as chlorogenic acid and 3,4,5-trihydroxybenzamide, which are used as co-dispersants for MnO2 and CNT. The dispersant interactions with MnO2 and CNT are discussed in relation to the chemical structures of the dispersant molecules and their biomimetic adsorption mechanisms. The dispersant adsorption is a key factor for efficient co-dispersion in ethanol, which facilitated enhanced mixing of the nanostructured components and allowed for improved utilization of charge storage properties of the electrode materials with high active mass of 40 mg cm−2. Structural peculiarities of the dispersant molecules are discussed, which facilitate dispersion and charging. Capacitive properties are analyzed using cyclic voltammetry, chronopotentiometry and impedance spectroscopy. A capacitance of 6.5 F cm−2 is achieved at a low electrical resistance. The advanced capacitive properties of the electrodes are linked to the microstructures of the electrodes prepared in the presence of the dispersants.
Highlights
Organic molecules, containing catechol groups, exhibit exceptionally strong adsorption on inorganic surfaces, which is a key factor for their applications for surface modification of various materials and fabrication of adherent coatings [1]
Various catecholate molecules were used as capping and structure directing agents for the synthesis of non-agglomerated nanoparticles, coated particles and nanorods with high aspect ratios [9,10,11,12,13,14]
The chemical structures of the molecules facilitated their adsorption on MnO2 and carbon nanotubes (CNT), which allowed for co-dispersion and enhanced mixing
Summary
Organic molecules, containing catechol groups, exhibit exceptionally strong adsorption on inorganic surfaces, which is a key factor for their applications for surface modification of various materials and fabrication of adherent coatings [1]. The adsorption mechanism of such molecules is similar to that of mussel proteins bonding to different surfaces, which results in super strong adhesion [2,3,4]. It is based on the bidentate chelating or bridging bonding of phenolic OH groups of the catechol ligands [1] to the metal atoms. The use of catecholate bonding mechanism has been gaining ground in the development of liquid-liquid extraction techniques [6], which facilitate the fabrication of non-agglomerated nanoparticles for diverse applications. It was found that metastable materials can be synthesized in the presence of catecholate molecules [15]
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