Fabrication of MnS/GO/PANI nanocomposites on a highly conducting graphite electrode for supercapacitor application

Highlights

• A wide surface area manganese sulfide nanoparticles were synthesized.

• In-situ polymerization of granular PANI over MnS/GO nanocomposite.

• Increases interface interactions between PANI and MnS/GO.

• Specific capacitance for nanocomposite MnS/GO/PANI was 773 F/g at 1 A/g.

Abstract

We demonstrate a high surface area of manganese sulfide (MnS) nanoparticles via a simple solution method and investigated its morphology, physicochemical, and electrochemical studies. For the first time, we attempted to exploit the polymerization of aniline without adding HCl, as it is corrosive to the metal sulfide. Instead, the acidic group present on the graphene oxide surface plays a significant role to some extent as an acidic dopant in the polymerization process. This in-situ polymerization results in the uniform coverage of granular PANI on the entire MnS/GO nanocomposite, which enhances the interfacial interactions between PANI and MnS/GO nanoparticles. The introduction of graphene oxide (GO) to pristine MnS improved the specific capacitance, surface area, and average pore size. And incorporating PANI to MnS/GO leads to an increase in the interfacial interaction between the different pore sized nanoparticles giving enhanced specific capacitance. The specific capacitance for MnS/GO/PANI nanocomposite as measured by galvanostatic charge-discharge measurements was found to be 773 F/g at 1 A/g current density, and even at higher current density, it showed a specific capacitance of 484 F/g at 3.8 A/g. The specific capacitance obtained for MnS/GO/PANI nanocomposite from CV shows 822 F/g at 10 mV/s and 315 F/g at 200 mV/s. The combinatorial effects without destroying the metal sulfide nanostructure can provide an alternate route to design, promising electroactive nanocomposites is an ideal choice as a cost-effective, next-generation high-performance supercapacitor application.

Introduction

The worldwide issues of depleting natural and non-renewable energy sources cause a significant interest in clean and sustainable energy [1]. The discontinuous conduct of clean energy creates an interest for ceaseless power conveyance, and energy storage and conversion device became crucial. Battery and supercapacitor have been created as an exceptionally encouraging candidate of energy devices, attributable to the energy density of batteries and a power density of supercapacitors. For meeting the energy and power density simultaneously, the hybrid supercapacitor devices are built utilizing battery and capacitive-type materials as positive and negative terminal materials individually.

Transition metal sulfides draw in colossal considerations to fill in as battery-type electrode materials of energy storage devices because of their higher electric conductivity than the comparing oxides. As of late, some metal sulfides NiS_x, CoS_x, VS₂, MoS₂, and so on, have been applied for anode materials. Aside from these sulfides, manganese sulfide (MnS) is an additional potential anode material for the ease and high abundance of Mn [2,3]; yet, the obstacle ruining its application lies in the helpless basic conductivity [4]. Monodispersed hollow shaft like nanosphere (HS-NS) and tetrapod nanorod (TP-NR) MnS nanocrystals are obtained utilizing an effortless template free aqueous procedure. The MnS nanocrystals are utilized as supercapacitor materials, and they show superior exhibitions. The TP-NR nanocrystals show a higher explicit capacitance of 704.5 F g⁻¹ contrasted with the HS-NS nanocrystals, and both show higher qualities contrasted with manganese oxide [5]. Along these lines, the combination of MnS with graphene oxide (GO) with high surface area and conductivity can be wanted to upgrade the electrochemical exhibitions. Also, it is accounted for that the various hierarchical structures can likewise offer some new demonstrations from the synergistic interactions between the nano building blocks, aside from the prevalence of the single component [6]. The graphene oxide’s two-dimensional structure can be utilized as the platform in the manufacturing procedure of composite materials, which can offer a high electrolyte/electrode interface [7]. The created α-MnS/rGO//α-Fe₂O₃/rGO asymmetric supercapacitors (ASCs) indicated the biggest expected window of 1.6 V when 3 M KOH was utilized as the electrolyte. The ASCs showed a most extreme explicit capacitance of 161.7 F g⁻¹ at a current density of 1 A g⁻¹, and the most elevated energy density of 57.5 W h kg⁻¹ at the power density of 800 W kg⁻¹ [8]. γ-MnS/reduced graphene oxide composites (γ-MnS/rGO) were made using an effortless one-pot aqueous technique. As a cathode material for supercapacitors, the γ-MnS/rGO-60 composite got under measurements of graphene oxide was 60 mg and exhibited an improved explicit capacitance of 547.6 F g⁻¹ at a current density of 1 A g⁻¹, and remarkable rate ability (65% capacitance maintenance at 20 A g⁻¹), with unrivaled cycling stability and electrochemical reversibility [9].

Electronically conducting polymers as polypyrrole, polyaniline (PANI), polythiophene, and poly [3, 4 ethylenedioxythiophene] can store and discharge charges through redox forms related to the π-conjugated polymer chains [10]. When oxidation happens (additionally alluded to as p-doping), charges from the electrolyte were moved to the polymer spine, and on the reduction ‘undoping,’ they were discharged back into the solution. For the most part, p-dopable polymers were increasingly steady than n-dopable ones. The doping/dedoping process happens all through the bulk of the anodes, offering the chance to accomplish high estimations of explicit capacitance. Among the leading polymers, polyaniline (PANI) has pulled in much consideration in multifunctional applications such as energy storage [[10], [11], [12]] and microwave absorbance [13] due to their minimal effort, controllable electrical conductivity, and simple procedure capacity [11]. Combined PANI with different carbon materials, for example, graphite oxide, graphene oxide, carbon nanotubes (CNTs), carbon fiber, and mesoporous carbon, appears to be a promising path for the upgraded electrochemical properties [10,11]. What is more, the strength, electrical conductivity, and redox conduct of PANI could be extraordinarily improved when fused with conductive carbon materials. For instance, Zhao and associates created and described elite supercapacitor electrodes (empty carbon spheres/PANI) combined utilizing in-situ polymerization process, and the cathode showed a most extreme explicit capacitance of 525 F/g [12].

As a two-dimensional carbon material, graphene displays various one of a kind and appealing physical, substance, mechanical, and electrical properties, for example, high hypothetical explicit surface area, uncommonly high electrical conductivity, and mechanical adaptability. The consolidation of graphene with PANI not only just fortifies the soundness and conductivity of PANI but also fundamentally improves its electrochemical exhibition. Indeed, GO can be not only just utilized as the conductive substrate for MnS particles but also additionally cling to join MnS and polyaniline intimately, which will advance the charge transfer process because of the synergism.

In this work, we have synthesized pristine MnS at room temperature via a facile solution-processed method, which was then well dispersed with high surface area GO at room temperature. The novelty of the work is, we attempted to exploit the polymerization of aniline without adding HCl, as it is corrosive to the metal sulfide. Instead, the acidic group present on the graphene oxide surface plays a role to some extent as an acidic dopant in the polymerization process for the first time. So far, binary nanocomposites have been reported, whereas the ternary composite, MnS/GO/PANI is a novel electrode material that enhanced the electrochemical performance. The specific capacitance for MnS/GO/PANI nanocomposite as estimated by galvanostatic charge-release estimations was seen as 773 F/g at 1 A/g, and even at higher current density, it showed a specific capacitance of 484 F/g at 3.8 A/g. The specific capacitance obtained for MnS/GO/PANI nanocomposite from CV shows 822 F/g at 10 mV/s and 315 F/g at 200 mV/s. This new MnS/GO/PANI composite material showing a high capacitance with excellent charge storage device with best rate capability is the novelty of this work.