Enhanced electrochemical and photocatalytic activity of g-C₃N₄-PANI-PPy nanohybrids

Highlights

• Chemical linking of g-C₃N₄ with that of PANI and PPy generated g-C₃N₄-PANI-PPy nanohybrids.

• The nanohybrids active towards multiple application sites of electrochemical detection of mebendazole drug and photocatalytic degradation of MB.

• The detection limit and quantitation limits of mebendazole are 0.1481 µM µA⁻¹ and 0.4717 µM µA⁻¹.

• The photocatalytic degradation of MB dye provided the maximum efficiency of 95.5%.

• These significant results confirm for the potential applications of g-C₃N₄-PANI-PPy nanohybrids as electrode and photocatalyst material.

Abstract

The present study deals with the synthesis, characterization, and testing of g-C₃N₄-PANI-PPy nanohybrids for electrochemical and photocatalytic studies. For the formation of nanohybrids, the chemical oxidative method was employed and was thoroughly characterized for the surface, functional, and elemental properties by making use of different instrumental techniques like XRD, XPS, FTIR, UV-Vis, Raman, FESEM, HRTEM, and EDAX. On testing of the electrochemical sensing properties, we found that the g-C₃N₄-PANI-PPy modified glassy carbon electrode (GCE) exhibited satisfactory results for the mebendazole drug detection and is supported by the formation of layer and donor-acceptor behavior corresponding to the electrochemical cyclic stability. Further, the g-C₃N₄-PANI-PPy nanohybrid investigated to have high photocatalytic performance towards the degradation of organic dye, methylene blue, and is supported by the enhanced specific surface area and transition of surface electrons. Finally, with such beneficial features of electrochemical sensitivity and great catalytic activity, the developed g-C₃N₄-PANI-PPy hybrid can find applications in the analytical laboratories and also catalysis research.

Introduction

In recent years, the increased production and usage of graphitic carbon nitride (g-C₃N₄) nanostructures is because of their intelligence to arrange themselves with a great assortment of nitride compounds that have significance in photocatalysis technology. Another attractive feature is the ability of these nanostructures to accept a massive number of structural geometries with an electronic structure that exhibits the semiconductor properties [1]. Since the g-C₃N₄ nanoparticles (NPs) containing composites exhibit excellent physicochemical properties taking advantage of their narrow size and high density of -NH₂ and -NH groups in a corner or edge surface sites. In scientific research, g-C₃N₄ is being used for the fabrication of sensors, DSSC and catalytic devices, fuel cells, and coatings for the passivation of surfaces against corrosion and photocatalysis [2], [3]. On the other hand, the metal nitrides such as tantalum nitride and niobium nitride are used in different ways [4]; for example, the scrape semiconductors are highly requisite excellence in particle size, such as photocatalysis, sensors, and DSSC applications. However, the use of g-C₃N₄ NPs in quantities sufficient to advance the scratch semiconductors affects its particle sizes. Further, it has been used as electrodes in electrocatalysis and water oxidation [5], [6], as cathodes in the counter electrode which shows photocatalytic properties. To prepare the C₃N₄ NPs, the commonly used methods include the hydrothermal technique and aminolysis [7], [8].

The g-C₃N₄ containing nitrides and other nanohybrids are investigated to serve as the highly active photocatalysts and such activity is due to the presence of defects in the structure of corundum type carbon allotrope for which the three defect species are in support includes the N-bonding N^4-, nitrogen vacancies, and C¹⁺ interstitials [9]. These species in general enhances the electron transport properties of semiconductors by either increasing or decreasing the total nitrogen content [10]. For example, the loss of nitrogen generates an extra electron in the polymeric molecule and so acts as an n-type semiconductor, while the addition/gain of nitrogen (entering the lattice as N^4-) creates a deficit of electrons (introduces electron holes) that serves as the p-type conductor. Therefore, with the addition or extraction of nitrogen in the conducting co-polymers, a transition from n to p-type response or vice versa can be introduced [11].

The chemical name of mebendazole (MBZ) is 5-benzoyl-2-benzimidazolecarbamic acid methyl ester and is a commonly used broad-spectrum anthelmintic drug that has high curing rates against the infestations associated with Ascaris, threadworms, hookworms, and whipworms [12]. This drug exhibits polymorphism and is marketed commercially in two different forms of tablets and oral suspension and so, several quantification techniques are being reported in the literature for the analysis of MBZ kind of polymorph drug [12]. Although many different methods are available, they all suffer from the limitations of efficacy, sensitivity, complex procedures, the need for expensive instruments, the requirement of trained personnel, etc. Therefore, it is highly required to have a simple and sensitive methodology for the qualitative and quantitative analysis of polymorphic drugs like MBZ which in general is difficult for efficient analysis.

Methylene blue (MB) is a commonly used organic dye in a majority of industries like paint, textile, wood, leather, food, pharmaceutical, and plastics and such extensive use of this dye is due to the color stability originates from the high gradation of aromaticity and extensive conjugation of chromophores [13]. This widespread use of MB dye causes the unwanted accumulation of MB dye and its related byproducts in the environment, in particular surface or groundwater, and from where enters the human and ecological systems and causes the serious effects [14]. Thus, there has been a very high demand for the development of sustainable methods towards the degradation of organic dyes like MB, and one approach in that direction includes the photocatalysis where the natural sunlight or UV radiation serves as a source of energy.

By taking into consideration the electronic and semiconductor properties of g-C₃N₄, the present work is aimed to test the efficacy of g-C₃N₄ containing polymer composite towards the electrochemical and photocatalytic applications. For the polymer-composite formation, we have selected the p-type polyaniline (PANI)-polypyrrole (PPy) polymer, as it can generate a band diagram with stable interfacial structures and an electron shift occurs through the addition of excess charges with a homogeneous counter charge at the background. Also, this work monitors and appreciates how the melamine gets transformed into g-C₃N₄ and the photocatalytic properties of g-C₃N₄ to be couturier by controlling the surface charge parameters. As we hypothesized that the photocatalytic activity can be possibly influenced by controlling the excess amount of charges from the dipoles forming at the interface of g-C₃N₄ and PANI-PPy, where the excess charges attract the counter charge at p-type of PANI–PPy hybrid interface. The polymer mixture of PANI-PPy is expected to serve as a significant catalyst because of its well-organized structure, morphology, number of free space groups in the crystal, amount of active catalytic centers, etc. Further, the PANI-PPy mixture when gets into contact with g-C₃N₄, we hypothesized that the formed nanohybrid can have more efficient properties because of the altered surface and electron transformation characteristics. Following the physicochemical characterization, the g-C₃N₄-PANI-PPy nanohybrids are being used for the electrochemical detection of MBZ oxidation, and the photocatalytic degradation of MB dye.