The supercapacitor is a high-capacitance capacitor that bridged the distance between electrolytic capacitors and rechargeable batteries. It usually stored 10-100 instances more electricity in step with unit quantity or mass than electrolytic capacitors. It can have supply rate a lot quicker than batteries and can tolerate many more rate and discharge cycles than rechargeable batteries [1-3].

Nano-substances have been utilized in a range of production process, merchandise and healthcare which includes paints, filters, insulation and lubricant additives [4]. Besides they found diverse applications in biosensing, biomaging, tumor diagnosis and antibiofouling [5]. Regarding supercapicator applications, [6-7] Metal oxides (RuO₂, MnO₂, In₂O₃, Co₃O₄, NiFe₂O₄, BiFeO₃ etc.) were preferred over others because of their low cost and environmental friendliness. The capacitor in which metal oxides is used as electrode material are said to be Among various metal oxides of  ruthenium oxide showed the higher specific capacitance value but it cannot be commercialized due to its toxic nature. Manganese is one of the best considerable materials to replace the ruthenium, since recent reports showed that the manganese based mixed metal oxides has higher capacitance value of above 200 F/g [8]. A novel epoxide-driven sol-gel process to prepared NiCo₂O₄ aerogels with ultrahigh specific capacity [9] and a self-assembly method by exfloating Ni-Co hydroxides and assembling with GO. This method provided the first insight into the feasibility of NiCo₂O₄-rGO composite material [10] synthesized halloysite-polyaniline-poly (sodium-p-styrenesulfonate)-polyaniline as electro-active materials and found that the specific capacity of surface modified halloysite was 137 F/g at a current density of 0.5 A/g. By adding the conducting polymers, the halloysite/pollypyrrole nanocomposite exhibits 522 F/g capacitance at 5 mA/cm² [11] used reduced graphene oxide (rGO) coated HNTs as the supercapacitor material, and a capacitance of 27.2 F/g at 0.2 A/g was obtained [12]. The nanocomposites of MoS₂ and VO₂ were found to have advantages for high-performance lithium ion storage, including expanded interlayer distances and fast electrochemical reactions [13-14]. They have been used to develop 3 dimensional graphene composites for supercapacitor application with optimal specific capacitance 268 F/g at a current density of 1.25 A/g [15]. It has also been reported that porous NiCo₂O₄ nanowires with supercapacitor applications [16,17]. The d-block element like Co, Ni Mn etc containing nanocomposites reflected versatile and useful properties. Cobalt manganese oxides is one of the potential candidates which showed the excellent capacitive behaviour due to higher oxidation potential of cobalt and more electrons transported by manganese pseudo capacitor which stored energy by redox reaction. Keeping in mind all the above, we have also presented a d-block element CoMn₂O₄ nanocomposite and reported its facile synthesis, characterization and its supercapacitor applications.

The experimental testing for this study was done through the lens of a current project for oil and gas majors. The industrial purpose is to determine potentially effective antifouling solutions to polymer wrapped pipes within marine environments. Current flow around a pipeline can result in vibration created by vortex shedding. The frequency of this vibration can become close to the natural frequency of the pipe, which can cause fatigue or damage the pipeline. A solution to this vibration is to wrap the pipe in a Vortex Induced Vibration (VIV) reducing strake. These strakes are a rotationally-moulded, high-density polyethylene wrap that completely encircle the pipe and change the trajectory of the flow around the pipeline. The materials and conditions in this study are based on the development of an antifouling HDPE VIV strake. The terms antimicrobial, antifouling, and biocidal all describe materials that resist microbial growth and will be used interchangeably throughout this study.

Antifoulant Materials

Antifouling testing was conducted utilizing eleven samples including a control sample. Each sample was produced using a combination of at least one the following antimicrobial powders: zinc oxide, cuprous oxide, copper nickel, zinc pyrithione, and a new, commercially available material called Antimicrobial Nano Alloy ANA) comprised of silver and aluminum oxide. Micron-scale zinc oxide powder was procured from Bulk Apothecary with a purity of 95%. Micron-scale cuprous oxide was procured from American Chemet Corporation with a purity of 95%. Copper nickel was procured from Richest Group and had a size of 10 micrometers and purity of 99%. Zinc pyrithione was procured from TCI and had a size of 5 microns and purity of 97%. ANA composed of a silver-aluminum alloy was procured from Buffalo Technology Group and had a size range of 0.5-10 micrometers and purity of 99%. Table 1 shows the blend of each substrate used in this project.

Preparation of CoMn₂O₄ Nanocomposite

0.873 mg cobalt nitrate hexahydrate (CoNO₃) (A.R Sigma Aldrich India) and 0.45 mg of manganese chloride (A.R Sigma Aldrich India) was added to the 30 ml deionise water. Cetyltrimethylammonium bromide (Sigma Aldrich India) solution (0.14 mg in 5 ml) was again added to the above solution. After stirring for 30 min a solution of potassium hydroxide (Thomas Baker India) (0.14 mg in 50 ml) was added by drop wise. The solution colour changed from pink to blue. The precipitate was separated by centrifugation at 5000 rpm for 20 minutes. The nanocomposite was washed and dried at 300 ºC for 3 hrs.

The synthesized nanocomposite was characterized by Fourier transform infrared (FT-IR) spectra (VERTEX 70, Bruker, India) at ambient temperature in the range between 600 cm⁻¹ to 640 cm⁻¹, thermogravimetric analyzer (TGA, Pyrisl TGA, Perkin Elmer, USA) and XRD using (Rigaku- Modal no Mini Flex 600, India). The different spectra and graphs were depicted as:

  XRD Analysis

The powder XRD patterns of CoMn₂O₄ nanocomposite is depicted in Fig.1. The peak at 31.20°(220), 36.75°(311), 44.7°(400), 59.3°(511) and 65.2°(440) shows formation of the crystalline nature of CoMn₂O₄ nanocomposite. The synthesized nanoparticles consisted of multigrain agglomeration with small discrete crystallites. All the crystallites were having different morphological structure with different dimensions. The average particle size of the product was determined using debye–scherrer formula and Bragg’s equation by fitting the (311) peak. The calculated size of nanoparticles was found to be below 40 nm and 21.75, which confirms the nano structure of the particle and moreover the calculated size matches with the result obtained from XRD. These peaks corresponded to the JCPDS card no.- 23-1237. The crystalline size of the nanocomposite was calculated from the Scherrer’s formula (Eq. 1)

            D = K λ / (βcosθ) (3) 23      ------- (1)

2-theta (deg) Intensity (cps) 20406080 0e+000 1e+004 2e+004 3e+004 4e+004

D = crystalline size, K = Dimensionless shape factor, β = line broadening at half the maximum intensity, λ = wavelength.

The crystalline size was found to be 21.75 nm with d-spacing of 0.24 nm as calculated from the Bragg’s law (Eq. 2):

             nλ = 2dsin?        -------- (2)

Figure 1: Powder XRD Patterns of CoMn₂O₄ Nanocomposite.

FTIR Studies

The FTIR study of CoMn₂O₄ nanocomposite was done to identify chemical bonds in the sample. The Fig.2 showed the FTIR spectrum of CoMn composite. The typical FTIR spectrum of CoMn was in agreement with previous work already done [18]. The characteristics peak at 1218 cm⁻¹, 1372 cm⁻¹, and 1744 cm⁻¹ corresponded to the C-N stretching, C-H bending in alkenes and C=O stretching. The peaks between 600 cm⁻¹ to 640 cm⁻¹ showed the formation of bond for CoMn₂O₄.

Figure 2: FTIR Analysis of CoMn₂O₄ Nanocomposite.

TGA analysis

TGA served as a valuable tool for understanding thermal events associated with nanomaterials when subjected to heating. The thermal properties of the nanocomposite CoMn precursor containing 0.01 g CTAB was characterized by the TGA analysis to determine the suitable thermal decomposition temperature for preparing CoMn₂O₄. From the TGA graph (Figure 3), we observed two measured weight losses. The first weight lost observed from 25° to 250°C is attributed to loss of water from the nanocomposite. The second weight lost from 250° to 300°C  is due to the thermal decomposition of Mn and Co oxalates into CoMn₂O₄ oxide in presence of air. So, from 300° to 800°C the material showed thermal stability. Hence, the nanocomposite showed  thermal stability in a range of temperature 300° to 800°C.

Figure 3: TGA analysis of CoMn₂O₄ Nanocomposite.

Cyclic Voltammetry Study

For studying electrochemical aspects, Cyclic Voltammetry study was utilized for synthesized CoMn₂O₄ nanocomposite using the instrument NOVA-1.10 in the potential window of 0.1 V to 0.8 V at the scan rate 5 mV/s. From the CV curve (Figure 4), it was clear that nanocomposite posses’ good pseudo capacitance behavior with good charged diffusion at the electrode surface.  Specific capacitance (Csp) as calculated as per the reported method (Eq. 3) with the help of the formula

Where  and   are the maximum value of the current in positive and negative scan respectively. V refers to the scan rate and m is the mass of the electrode material.

The specific capacitance of the CoMn₂O₄ was found to be 1120 F/g, which is a very high value. Hence the synthesized nanocomposite material could be used for storing the electrical charge inside it.

The present article represented the synthesis of nanocomposite of CoMn₂O₄ using the co-precipitation method. The synthesized nanocomposite material was characterized by XRD, FTIR and TGA. The study showed that the structure of CoMn₂O₄ is crystalline in nature and was thermally stable. The specific capacitance of the material was found to be 1120 F/g, which reflect that the nanocomposite CoMn₂O₄ material prepared would act as a useful material for storing electric charge inside it.

We highly acknowledge Head of the Institute (Dr. Bashir Ahmad Dar) and department of chemistry, Govt Degree College Shopian for their support throughout the work. M. A. Kaloo gratefully acknowledges Department of Science and Technology, New Delhi for INSPIRE FACULTY research grants [DST/ INSPIRE/04/2016/000098].

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