Faculty Publications
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Item Single step synthesis of rGO, copper oxide and polyaniline nanocomposites for high energy supercapacitors(Elsevier Ltd, 2018) Viswanathan, A.; Nityananda Shetty, A.N.Reduced graphene oxide, copper oxide and polyaniline (GCP) nanocomposites possessing energy densities close to many of Li-ion batteries are synthesized by facile in-situ single step chemical method by varying the weight percentage of each of the constituent materials. Of all the composites synthesized, the one with weight percentage of G12%: Cu2O/CuO40%: P48% (G12CP) exhibits the maximum specific capacitance of 684.93 F g?1, specific capacity of 821.91 C g?1, energy density of 136.98 W h kg?1, and power density of 1315.76 W kg?1 at the current density of 0.25 A g?1. The composite shows the retention of 84% of its initial capacitance up to 5000 cycles at a scan rate of 700 mV s?1. The electrochemical performance of G12CP is superior to the performances of other ternary composites and those of binary composites synthesized with respective weight ratios as that of G12CP composite. The potential of G12CP to act as a secondary power backup device is successfully demonstrated and the performance obtained is comparable with some of the previously reported similar works, and even superior to some others. © 2018 Elsevier LtdItem High energy reduced graphene oxide/vanadium Pentoxide/polyaniline hybrid supercapacitor for power backup and switched capacitor converters(Academic Press Inc. apjcs@harcourt.com, 2019) Viswanathan, A.; Prakashaiah, B.G.; Subburaj, V.; Nityananda Shetty, A.N.The robust reduced graphene oxide (rGO)/vanadium pentoxide (V 2 O 5) /polyaniline (PANI) nanocomposite with a weight percentage of rGO – 5.88%: V 2 O 5 – 11.76%: PANI – 82.36%, was synthesized by facile insitu single step chemical method and fabricated into a supercapacitor device. The supercapacitor exhibited high energy density of 54.62 W h kg ?1 and an exceptionally high sustainability of its performance up to 13,000 rechargeable cycles at high charge/discharge rate. The high energy density was further confirmed when the supercapacitor containing the afore mentioned composite, acted as an excellent secondary power source to store and deliver energy for substantially long time when charged at an exceptionally high current using a commercial 9 V battery. Further, its energy storage and delivery capabilities were established by using it in a real time switched capacitor converter circuit and the obtained performance for potential step up and step-down purposes were gratifying. The obtained electrochemical parameters included a maximum specific capacitance of 273F g ?1 specific capacity of 327.6C g ?1 , energy density of 54.62 W h kg ?1 and a power density of 1636.5 W kg ?1 at a current density of 1 A g ?1 . © 2019 Elsevier Inc.Item Real time magnetic supercapacitor with antiferromagnetic nickel hydroxide based nanocomposite(Elsevier Ltd, 2019) Viswanathan, A.; Nityananda Shetty, A.N.An antiferromagnetic, semiconducting nickel hydroxide (Ni(OH) 2 ), with a good theoretical capacitance is composited with reduced graphene oxide and polyaniline to synthesize the electrode material for energy storage in supercapacitors. The composite overcomes the limitation of low conductivity of nickel hydroxide. The conductivity and antiferromagnetic nature of nickel hydroxide are altered by applying magnetic field, which in turn enhances its energy storing capacity. A ternary composite with the weight percentages of 4%: 48%: 48% of reduced graphene oxide/nickel hydroxide/polyaniline (GN48P), respectively, exhibits a magnetic susceptibility of 850. The application of a magnetic field of 625 ?T results in an enhancement of performance of the composite, exhibiting a specific capacitance of 19.14 F g ?1 , specific capacity of 22.97 C g ?1 , energy density of 0.6649 W h kg ?1 , a power density of 17.57 W kg ?1 at a current density of 0.25 A g ?1 and retention of 85.19% of its original capacitance up to 5000 cycles. This premier study on the effect of magnetic field, on the electrochemical performance of the supercapacitor in a typical two electrode system showed 69.4% increase in its specific capacitance. © 2019 Elsevier LtdItem The high energy supercapacitor from rGO/Ni(OH)2/PANI nanocomposite with methane sulfonic acid as dopant(Academic Press Inc. apjcs@harcourt.com, 2019) Viswanathan, A.; Nityananda Shetty, A.N.The low energy densities of supercapacitors limit their utilization as energy storage and energy conversion devices. To overcome this limitation, here we present a ternary nanocomposite of reduced graphene oxide (rGO)/nickel hydroxide (Ni(OH)2/polyaniline (PANI), with methane sulfonic acid as dopant, having weight percentages of 14%:14%:72% (G14NP), respectively, as an electrode material for supercapacitor. With 1 M sulfuric acid (H2SO4) as the electrolyte, the supercapacitor yields a high energy density of 120.48 W h kg?1, comparable with those of Li-ion batteries. The G14NP also exhibits good electrochemical performance with a specific capacitance of 602.40 F g?1 and a power density of 2584.83 W kg?1, at a current density of 1 A g?1. The G14NP also exhibits a promising stability of its electrochemical performances even after 16,500 cycles at a potential scan of 400 mV s?1. Remarkably, the composite performs exceptionally well at a potential window available in an aqueous electrolyte. The sustainability to high current loading while charging and its power backup application is satisfactorily demonstrated, by charging with a commercial 9 V battery. © 2019 Elsevier Inc.Item Effect of dopants on the energy storage performance of reduced graphene oxide/polyaniline nanocomposite(Elsevier Ltd, 2019) Viswanathan, A.; Nityananda Shetty, A.N.The nanocomposites comprising of reduced graphene oxide (rGO) and polyaniline (PANI) were synthesized by facile insitu single step chemical methods, with glacial acetic acid (AA) and methane sulphonic acid (MSA) as dopants for PANI. The rGO/PANI nanocomposites synthesized with the similar weight percentages of constituents exhibited better electrochemical performance in the presence of MSA than in the presence of AA, in the real two-electrode supercapacitor cell system. The nanocomposite of weight percentages of rGO-6.7%, and PANI-93.33% (GP93MSA), with MSA as dopant exhibited a remarkable feature of increase in energy storage when the number of cycles was increased. It exhibited a maximum enhancement of 237.44% in its energy storage performance, after 13600 cycles as compared to the performance before the onset of cyclic test. The high performances obtained with GP93MSA include high specific capacitance of 512.82 F g?1, specific capacity of 615.38 C g?1, energy density of 102.56 W h kg?1 and a power density of 1.8954 kW kg?1 at 1 A g?1. The energy density of the supercapacitor with GP93MSA as the electrode material, is of the same order as that of Li-ion batteries. Also, GP93MSA showcased good cyclic stability up to 23000 cycles. © 2019 Elsevier LtdItem Reduced graphene oxide/vanadium pentoxide nanocomposite as electrode material for highly rate capable and durable supercapacitors(Elsevier Ltd, 2020) Viswanathan, A.; Nityananda Shetty, A.N.The nanocomposite from reduced graphene oxide (rGO) and vanadium pentoxide (V2O5) was synthesized by the chemical method to obtain a nanocomposite of rGO 7.69% /V2O5 92.31% (GV). The role of faradaic V2O5 in storing high energy, in combination with rGO was studied and the energy storing parameters were determined from the liner discharge (from the slope of the discharge curve) approach and the non-linear discharge approach (from the integrated area of the discharge curve). The appropriateness of these methods is a matter of diverse views among the researchers when the specific capacitance (Cs) of the composite electrode material, comprising of both non-faradaic and faradic material, has to be determined. The energy storage parameters obtained from these two different approaches are found to be differing to a large extent. The energy storage parameters obtained from linear discharge approach are, a high specific capacitance (Cs) of 120.62 F g?1, a specific capacity (Q) of 144.74 C g?1, an energy density (E) of 24.12 W h kg?1 a power density (P) of 2.647 kW kg?1 and a columbic efficiency (?) of 79.22% at a current density of 2 A g?1. The nanocomposite retained 100% of its initial Cs up to 5000 cycles. Also retained 38% of its initial Cs, after 10,600 cycles at a potential scan of 400 mV s?1. © 2019Item High rate capable and high energy supercapacitor performance of reduced graphene oxide/Al(OH)3/polyaniline nanocomposite(Academic Press Inc., 2020) Viswanathan, A.; Gururaj Acharya, M.; Nityananda Shetty, A.N.The high rate capable, high energy (higher than the lead acid batteries & Nickel-cadmium batteries and comparable with Li-ion batteries) and long lasting supercapacitive performance was achieved from a ternary nanocomposite of rGO/Al(OH)3/PANI (5.88%:11.77%:82.85%) (GAlP82). The GAlP82 exhibited high cyclic stability till 47,500 cycles at 400 mV s?1, with increasing trend of specific capacitance (Cs) with increase in No. of energy storage/delivery cycles. After 41,500 cycles the GAlP82 exhibited a Cs of 490.19 F g?1, an energy density (E) of 98.03 W h kg?1 and a power density (P) of 2.2829 kW kg?1 at 1 A g?1. The GAlP82 exhibited a good rate capability by retaining 73% of Cs up to 10 A g?1 before cyclic stability study and 33% of Cs up to 23 A g?1 after 41,500 cycles; and all these impressive performances are achieved from the symmetric supercapacitor cell of GAlP82. © 2020 Elsevier Inc.Item Enhancement of supercapacitance of reduced graphene oxide, copper oxide and polyaniline using the mixture of methane sulphonic acid and sulphuric acid as electrolyte(Elsevier Ltd, 2021) Viswanathan, A.; Nityananda Shetty, A.N.The mixture of mineral acid and organic acid as aqueous electrolyte for the rGO12%: Cu2O/CuO40%: PANI48% (G12CP) nanocomposite, exhibited superior energy storage performance. The acid mixture electrolyte used is 0.4 M H2SO4 + 0.4 M CH3SO3H (1:1) (SA + MSA) and it exhibited enhanced diffusion and kinetic features in comparison with the bare 0.4 M H2SO4 (SA) and 0.4 M CH3SO3H (MSA). SA + MSA provided 16.8% higher energy storage than the SA and the performance obtained after 5000 charge/discharge cycles is 276.98% higher than the performance obtained before the cyclic stability test using the same acid mixture electrolyte. The G12CP provided a specific capacitance (Cs) of 490.19 F g?1, an energy density (E) of 98.0392 W h kg--1 and a power density (P) of 1.500l kW kg?1 at 1 A g?1 in the presence of SA + MSA. The obtained E is comparable with E of Li-ion batteries, Ni-metal hydride batteries, Na-S batteries, and Na-metal chloride batteries. © 2020 Elsevier LtdItem Quick responsive and durable supercapacitive performance of rGO/Zn(OH)2/PANI nanocomposites(Springer, 2021) Viswanathan, A.; Nityananda Shetty, A.; Bharath, S.P.; Mahendra, K.The quick responsive and durable supercapacitive performance was achieved from reduced graphene oxide/zinc hydroxide/polyaniline (rGO5.88%/Zn(OH)211.77%/PANI82.35%) (GZnP82) nanocomposite, synthesized by in-situ single step. The GZnP82 provided a specific capacitance (Cs) of 173.60 F g?1, a specific capacity (Q) of 208.32 C g?1, a specific energy of 34.7220 W h kg?1 and a specific power of 1516.8 W kg?1 at 0.25 A g?1. The GZnP82 exhibits only 28% decay of its initial Cs up to 12500 cycles at 2 A g?1. The GZnP82 is fast in response with the relaxation time (?) of 1.52 s. The capacitance of GZnP82 device obtained from impedance spectroscopy is 1.29 F. The comparison of electrochemical performance of GZnP82 measured from both chronopotentiometry and impedance spectroscopy, with similar reported energy storage materials, apprises that the achieved performances are of similar order; and better than, the reported materials. Most importantly, the addition of Zn(OH)2 has rendered the negative contribution to the GZnP82, as the binary combination of it, the rGO/PANI furnished higher performances than the GZnP82. © 2021, Indian Academy of Sciences.Item Superior supercapacitance exhibited by acid insoluble Ni(OH)2 in the form of its nanocomposite with rGO(Elsevier Ltd, 2022) Viswanathan, A.; Acharya, M.G.; Prakashaiaha, B.G.; Nityananda Shetty, A.N.The solubility of Ni(OH)2 in acids was been the major impediment that has been preventing the usage of acid electrolytes like 1 M H2SO4 in supercapacitors and batteries that contain Ni(OH)2 as electrode material. This impediment is successfully removed and impressive energy storage characters were achieved from an electrode made up of Ni(OH)2 in the presence of acid electrolyte of 1 M H2SO4. This acid insoluble form of Ni(OH)2 was achieved by synthesizing it in situ in the presence of graphene oxide by chemical reduction method to produce the stable nanocomposite of reduced graphene oxide (rGO) and Ni(OH)2. The insolubility of Ni(OH)2 in 1 M H2SO4 was carefully studied for nearly six months and proved to be a factual observation. Remarkably, the rGO/Ni(OH)2 composite exhibited the better energy storage performance in the presence of 1 M H2SO4 in relation with conventional methods that involve basic electrolytes like NaOH and KOH for Ni(OH)2. The supercapacitor containing rGO/Ni(OH)2 composite and 1 M H2SO4, was stable in storing and delivering the energy without deterioration up to 31,500 cycles, with an uniqueness of increase in energy storage with increase in cycles of energy storage and delivery. Remarkably, two type of faradaic processes are observed to be contributing to the total energy storage of Ni(OH)2, of which one is unprecedented. The superior specific energy (E) and specific capacitance (Cs) achieved are 130.7175 W h kg−1 (comparable with Li-ion batteries of 3 V) and 653.5947 F g−1 at 1 A g−1. This superior Cs is higher than the theoretical Cs expected from this composite for this specific composition (rGO33.33 % and Ni(OH)2 66.66 %) (1571 F g−1) and higher than the theoretical Cs of Ni(OH)2 (2082 F g−1). It is expected that this study would be an inevitable attraction and take the applicability of Ni(OH)2 to higher level and make it one of the meritorious materials for future energy storage. © 2022 Elsevier Ltd