Electrocatalytic Activity of Asymmetrical Cobalt Phthalocyanines in the Presence of N Doped Graphene Quantum Dots: The Push‐pull Effects of Substituents

Abstract

A series of Co phthalocyanine (CoPc) derivatives and their respective nitrogen doped graphene quantum dot conjugates were used as catalysts towards the electrooxidation of hydrazine. Using a glassy carbon electrode as a support for the electrocatalysts, through cyclic voltammetry and chronoamperometry, the effects of combining the CoPcs with the nitrogen doped graphene quantum dots (NGQDs) were studied. The general observations made were that the NGQDs improve the catalytic activity of the CoPcs in both the π‐π stacked and covalently linked conjugates by increasing the sensitivities and lowering the limits of detection with values as low as 0.43 μM being recorded.

Creating the Ideal Push‐Pull System for Electrocatalysis: A Comparative Study on Symmetrical and Asymmetrical Cardanol‐based Cobalt Phthalocyanines

“…Tafel slope values ranging from 268 to 422 mV/decade (Table 1) were recorded for all the asymmetrical probes while the electrode modified with the symmetrical molecule, GCE‐ 5 , yielded the most desirable Tafel slope with a value of 91.9 mV/decade. These values are fairly high in comparison to previous reports based on the electrocatalysis of hydrazine using asymmetrical CoPc derivatives [13]. Tafel slopes higher than the normal 60–120 mV/decade have no kinetic meaning and suggest adsorption of either the products and/or intermediates on the modified electrode surface [33].…”

“…In addition to that, how the pairing affects the solubility of the overall molecule as well as the electronic behaviour still has to be explored. Previous reports have shown that alkyl‐based substituents (electron‐donating) have a significant effect on how the overall molecule functions [13]. However, this was based on an electrochemical study with very little information on the spectroscopic behaviour of the molecules being provided [13].…”

“…Previous reports have shown that alkyl‐based substituents (electron‐donating) have a significant effect on how the overall molecule functions [13]. However, this was based on an electrochemical study with very little information on the spectroscopic behaviour of the molecules being provided [13]. In this paper, we report on the synthesis and characterization of cardanol‐based push‐pull systems where the electron‐donating groups are kept constant while the substituents that bear the electron‐withdrawing groups are altered (complexes 1 – 4 ) along with the tetra‐substituted analogue, complex 5 , composed solely of electron‐donating groups, Scheme 1.…”

“…Hydrazine, although useful in various industries such as pharmaceutics as well as in the production of pesticides, is a dangerous chemical that needs efficient monitoring hence its selection as a test analyte [14]. Although asymmetric phthalocyanines have been employed for the electrocatalytic oxidation of hydrazine [13, 15], this is the first time that a systematic study of asymmetrical Co phthalocyanines where the push substituent is kept constant and the pull substituents are varied. The work presents a structure‐activity relationship which will help in the design of future electrocatalysts based on phthalocyanines.…”

Fast‐response Electrochemical Detection of Trinitrotoluene at Sub‐ppb Levels on Nitrogenized Porous Carbon Spheres

“…Among trinitrotoluene detection techniques such as nuclear magnetic resonance spectroscopy , mass spectroscopy and fluorescence , electrochemical sensing possesses high sensitivity, simple instrument, easy of operation and suitability for portable devices . To improve the performance of electrochemical detection of trinitrotoluene, one of the most popular approaches is to modify electrodes using carbon materials that have high specific surface area, good electrical conductivity and physical/chemical stability . Till date a series of carbon materials including multi‐walled carbon nanotube (MWCNT) , single‐walled carbon nanotube (SWCNT) , graphene and mesoporous carbon (MC) have been utilized.…”