Introduction

The word nano means dwarf is derived from the Greek word nanos [1]. Nanoparticles are defined as particles between 1 and 100 nanometers in size. Nanoscience and nanotechnology are the analysis of very small particles and have many applications in engineering, chemistry, physics, biology, and material science. Nanostructure science is a broad and multidisciplinary field of research and development, which has been growing exponentially worldwide in recent years. Nanoparticles have several applications in the fields of healthcare, electronics, agriculture, automobiles, optical, magnetic transport, photochemical, electrochemical, catalytic, and mechanical behavior [2].

Lithium-containing transition metal vanadium oxide nanoparticles have wide applications in the field of rechargeable batteries due to their high cell voltage and spinal or inverse spinal structure [3]; there are LiNiVO4 [4, 9,10,11], LiMnVO4 [5], LiCoVO4 [6], LiNiCoVO4[7], and LiNiMnVO4[8]. Here, Li and transition metal occupy the octahedral site. V atom occupies the tetrahedral site, and the 32e site by O ions [12]. In the latter years, LiNiVO4 nanomaterials have been largely used as high-voltage lithium cell materials for many applications in electric vehicles, plug-in hybrid electric vehicles, removal of low energy density cells, health hazards, and small cell applications.

The group VA transition metal oxides exhibit efficient photocatalytic activities under visible light irradiation [12]. A massive scientific investigation has been carried out on the preparation, characterization, and photodegradation studies of VA transition metal oxides, such as V2O5 [13], LaVO4 [14, 15], BiVO4 [16], Sn2Nb2O7 [17], Ag3VO4 [18, 19], ZrV2O7 [20], LiNiVO4 [12], CaZnV2O7 [21], NiVO3 [22], Ni3V2O8 [23], Ni2FeVO6 [24], and Ni3V2O8 [25]. Among this inverse spinal structure of LiNiVO4 NPs shows superior photodegradation activity under visible light illumination. Here, Li+ and Ni2+ ions were distributed in octahedral sites. V5+ ion residue was distributed in the tetrahedral site. In the LiNiVO4 lattice, multi-valence electrons of Ni and V ions might be present. The deintercalation process of Li+ ions leads to the oxidation of NiII into NiIII oxidation states, and it is due to the non-oxidative of V atoms. When LiNiVO4 is exposed to visible light, electrons are produced by photoreceptors. Then, electrons are transferred from oxygen 2p orbitals to the empty 3d Ni orbitals or by transfer of electrons from O 2p to the empty 3d V5+ orbital [12]. Therefore, H+ (holes) and free electrons are generated on the surface of the photocatalyst. These convert toxic organic dye into a nontoxic degradable product. The photodegradable properties mainly depend on grain size, synthetic method, and sintering temperature.

Many methods have been used to synthesize LiNiVO4 nanoparticles such as hydrothermal [26], solid state [10], sol–gel [7, 11], and Pechini method [12]. In this paper, lithium nickel vanadate nanoparticles are first time prepared by combustion method. It is a simple, inexpensive, easy, high yield, and energy-saving method. In nanoparticle synthesis, chemicals like polyvinyl alcohol, ascorbic acid, and sodium citrate are used as reducing and capping agents. These chemicals are always toxicant to nature which leads to pollution in the environment. However, to overcome this problem, plant biomass/juice such as Aloe barbadensis [27], Carica papaya [28], Corymbia citriodora [29], Eucalyptus globules [30], and Lycopersicon esculentum [31] has been used as a fuel. They act as a capping and reducing agent and are low-price, nontoxic, and environment friendly.

In this study, LiNiVO4 NPs use the green synthesis followed by the solution combustion method. Here, jackfruit seed extract was employed as taken initially for the green synthesis reaction. Jackfruit (Artocarpus heterophyllus) [32] belongs to the Moraceae family, which has antioxidant, anti-inflammatory, antifungal, hypoglycemic, and wound-healing properties. It also played a very important role in the reduction of metal ions into nanoparticles due to their bioactive substances like flavonoids and alkaloids in the extract. Within the framework of these criteria, XRD, SEM, EDS, FTIR, Raman, and UV–vis analysis were applied to characterize the properties of synthesized products. Additionally, textile industries’ waste organic product like methylene blue was used to analyze efficient photocatalytic activities of LiNiVO4 NPs under visible light irradiation and also tested the electrochemical impedance spectroscopy.

Experimental section

Materials and methods

Lithium carbonate (Li2CO3, 99%), nickel nitrate (Ni(NO3)2, 99%), ammonium vanadate (NH4VO3, 99%), potassium chloride (KCl, 99.9%), and methylene blue (MB, 97%) was purchased from SD Fine Chemicals. All the chemicals used were analytical grade and used without further purification.

Preparation of jackfruit extract

Fresh and unripe jackfruit was procured from IIHR, Bangalore. The jackfruits  were meticulously washed, cut into small pieces, and subsequently dried. These dried pieces were then blended to produce jackfruit flour. The obtained flour was transferred to a Soxhlet extractor, and extraction was conducted using distilled water as a solvent.The resulting extract was collected and stored in the refrigerator for subsequent experiments.

Preparation of lithium nickel vanadate nanoparticles

Lithium nickel vanadate was synthesized by a simple combustion method. For the synthesis of LiNiVO4 nanoparticles, tender jackfruit seed extract was taken as fuel. A stoichiometric amount of lithium carbonate (Li2CO3), nickel nitrate (Ni(NO3)2), and ammonium vanadate (NH4VO3) was taken in a silica crucible. To this, different volume of fuel was added (2 ml, 4 ml, 6 ml, and 8 ml) and labeled as LNV1, LNV2, LNV3, and LNV4, respectively. Further, this mixture was placed on a hot plate with continuous stirring to get a homogeneous mixture. Then, this series of LiNiVO4 was subjected to preheated muffle furnace at 400 °C for about 10 min separately. Calcination was carried out to remove impurities from the synthesized product at 500 °C for 5 h. Finally, pure, olive-green color lithium nickel vanadate was obtained and used for further analysis.

Characterization

The crystallinity and purity of the synthesized LNV NPs were identified using an XRD in the Rigaku smart lab (cu-kα). The elemental analysis, particle size, and morphology of the nanoparticles were elucidated by TESCN Vega 3LMO SEM. UV–vis spectrophotometer was used to analyze the optical properties of the NPs (Agilent Cary 60). The functional groups of the nanoparticles were recognized using an FTIR spectrophotometer (FTIR-Bruker Alpha). The range of wave numbers is between 400 and 1200 cm−1. The Raman measurement of synthesized nanoparticles was recorded by using Horiba Xplora plus Raman spectroscope.

Photodegradation study of nanoparticles

Lithium nickel vanadate nanomaterials were synthesized by the combustion method. The photo-degradation efficiency of LiNiVO4 NPs was evaluated by using methylene blue dye under visible light radiation using a 300 W/230 V AC tungsten lamp at room temperature. The different parameter effects of photodegradation such as different concentrations of catalyst load, variable dye concentration, pH variation, and scavenger activity have been studied using LiNiVO4 nanoparticles. In this method, a known amount of photocatalyst (10–70 mg) was mixed with 100 ml of MB solution (5 ppm). Further, this mixture was added under a dark chamber with continuous stirring for about 30 min to observe adsorption/desorption between photocatalyst and methylene blue organic dye. After that, around 2 ml of the mixture was withdrawn from the photoreactor, followed by a centrifugation to remove the catalyst. The sample was subjected to visible light at wavelength 664 nm. The percentage of degradation was calculated using the following formula.

$$\text{Degradation percentage}=\frac{{C}_{0}-{C}_{f}}{{C}_{0}} \times 100$$
(1)

where \({C}_{0}\) is the initial absorbance and \({C}_{f}\) is the final absorbance of every 30 min.

Modified electrode preparation for electrochemical study

5 mM KCl and three-electrode cyclic voltammetry were used to analyze the EIS of lithium nickel vanadate nanoparticles. 4 mg of the sample was dissolved in deionized water and sonicated for up to 10 min. The impurities on the surface of the glassy carbon electrode were removed by polishing using MRE paper (1.0, 0.3, and 0.05 different grain sizes) for 3 min. The surface of the electrode was coated by a drop casting technique and dried for 4 h. For the analysis of EIS, glassy carbon, platinum, and silver-silver electrodes were used as a three-electrode system.

Result and discussion

X-ray diffraction studies

XRD pattern of lithium nickel vanadate nanoparticles prepared by combustion method was represented in Fig. 1. It clearly shows the inverse spinel structure of LiNiVO4 nanoparticles [11]. Here, octahedral sites were occupied by Li and Ni atoms, vanadium ions were occupied on the tetrahedral sites (8a), and O atoms were on the 32e site [33]. The most intense line (220) indicates the transition metal atom present in the tetrahedral site. All four XRD patterns exhibit diffraction-dominated peaks at 2 \(\theta\) = 36.28° and 30.84° related to the crystal planes of (220) and (311), respectively. This shows the strong crystalline nature of the nanoparticles [34]. The peaks labeled as * and # indicate the minute quantity of Li3VO4 and NiO impurities in the LiNiVO4 NPs, respectively (according to several earlier researchers) [9, 34,35,36,37,38]. Using Debye Scherer’s formula, the crystalline size of the LiNiVO4 nanoparticles was calculated. The average crystalline size of the lithium nickel vanadate nanoparticle is 55 nm.

Fig. 1
figure 1

XRD analysis of LiNiVO4 NPs fabricated by combustion method (* -Li3VO4, #—NiO)

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$$D=\frac{0.94\uplambda }{\beta COS\theta }$$
(2)

Here, D is the average size of the crystal, \(\lambda\) is the wavelength of the X-ray source, \(\theta\) indicates Braggs diffracting angle, and β is the full width at half maximum.

The lattice strain (ɛ) is an interesting structural parameter of LNV NPs and is calculated using the following equation

$$\varepsilon =\frac{\beta }{4\;\text{tan}(\theta )}$$
(3)

The dislocation density of the LNV NPs was calculated using the below expression

$$\delta =\frac{1}{{D}^{2}}$$
(4)

The stacking fault energy of LNV NPs was calculated using the following equation.

$$2{\pi }^{2}/45{\left(3\;\text{tan}\theta \right)}^{1/2}$$
(5)

The lattice constant was calculated using the following equation and is tabulated in Table 1.

$$\alpha ={d}_{\text{hkl}}\sqrt{{h}^{2}+{k}^{2}+{l}^{2}}$$
(6)

where h, k, and l are the Miller indices, and d is the interplane spacing of the crystal plane. It was observed that with increasing the fuel concentration, the lattice constant also increases from 6.141 to 6.203 Å. The calculated lattice strain and dislocation density are given in Table 1. It clearly explains that as the crystallite size increases, lattice strain and dislocation density decrease due to lattice imperfection. The stacking fault energy of LNV1 NPs is greater compared to LNV4 NPs due to their particle close together (Fig. 2).

Table 1 Crystallographic data of LNV NPs
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Fig. 2
figure 2

Crystalline structure of LNV nanoparticles synthesized by combustion method

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Morphology study of nanoparticles

Figure 3 illustrates the SEM images of LiNiVO4 nanoparticles synthesized by the combustion method using different concentrations of jackfruit seed extract as fuel. The images indicate the formation of agglomerated and clustered with almost spherical and needle structure morphology. During the synthesis, high energy generated from the muffle furnace even leads to the agglomeration of nanoparticles. The size of the nanoparticles decreases as the concentration of the fuel increases. Particle is in the range from 74 to 88 nm and also agglomeration increases with an increase in fuel concentration [9, 35]. Figure 3 (e) shows the energy dispersive X-ray spectrometry (EDS). This represented the elemental composition of synthesized lithium nickel vanadate NPs. The analysis of EDS shows the existence of V, Ni, and oxygen elements (Table 2). Also, the presence of Ni: V in the average ratio is 1:1. however, the Li element cannot be detected because of the lightest metallic element [12] [39].

Fig. 3
figure 3

SEM and EDS images of LNV4 nanoparticles synthesized using the combustion method

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Table 2 Chemical composition of LiNiVO4 NPs
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Analysis of Fourier transforms infrared technique

Figure 4 represents FTIR spectra of LiNiVO4 nanoparticles in the 400–4000 cm−1 range. Different bands located at 630, 673 and 786 cm−1 have been specified to VO4 tetrahedrons stretching vibrations and also inverse spinel structure of characteristic vibrational bands. The asymmetrical stretching of Li-O in LiO6 octahedrons was observed at 411 cm−1 region. There is a small peak around 1036 cm−1 which indicates Li+-O-V band interactions. FTIR spectrum produces all the possible vibrational bands of LiNiVO4 [10]. The peak at 1647 cm−1 is attributed to the bending H-O-H vibrational band. It is confirmed that some of the water molecules are attached to the LNV NPs. The peak that appeared in the higher frequency region at 3152 cm−1 represents the hydroxyl group stretching vibration of tetravalent vanadium [33, 34, 36].

Fig. 4
figure 4

FTIR spectral studies of LiNiVO4 nanoparticles

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Raman spectroscopy analysis

The vibrational property of the synthesized LiNiVO4 nanoparticles was represented in Fig. 5 by using Raman spectroscopy. The different peaks of LiNiVO4 are located at 327 cm−1, 817 cm−1, and 950 cm−1 corresponding to A1g+ Eg +F2g fundamental phonon modes of cubic spinal, respectively. Intense broadband is observed at 700–850 cm−1 and is assigned to tetrahedron VO4 stretching frequencies. This is probably due to the vibration between the highest oxidation state cation (V5+) and oxygen. This broadband is located at 817 cm−1 and indicates the A1g symmetry of the VO4 tetrahedron. While the band in the 327 cm−1 region is ascribed to the VO4 tetrahedron of bending mode with E symmetry. The peak at 372 cm−1 indicated Li-O, and the peaks at 505 and 630 cm−1 indicated Li-O-Ni asymmetric stretching frequencies [10, 12, 37]. An ideal stretching frequency of VO4 tetrahedron of Raman spectra is located at 788 cm−1. In lithium nickel vanadate, the observed band was at 788 cm−1, valid for all Li structures. For LiNiVO4, high-frequency band is located at 817 cm−1, which is mainly dependent on Li concentration. Maybe this is because each oxygen is bonded to lithium and nickel cations in the VO4 tetrahedron [10, 37].

Fig. 5
figure 5

Raman spectral analysis of LiNiVO4 nanoparticles

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UV–visible studies

Figure 6 indicates the UV–visible spectra of LiNiVO4 NPs. The spectrum clearly shows two absorption bands of 465 and 728 nm. The spectra at longer wavelengths can unmistakably indicate the octahedral d-d spin allowed the transition from Ni2+ ion that is 3A2g (F) → 3T1g (F). The band gap shift has two possible charge transfers between respective metal ions [Ni (II), V(V)] and between ligand ions. The one charge transition is from oxygen to central vanadium metal atom (VO43−) group. Also, another one is from Ni (II) ion spin allowed d-d transition of 3A2g (F) → 3T1g (P) [7, 33, 34, 39]. Generally, the absorption bands related to metal–ligand and metal–metal charge transfer are difficult to explain because of the presence of expected overlap in the UV–Vis spectral region. The band gap energy of LiNiVO4 NPs was calculated using the Tauc equation from this absorption spectrum [40, 41].

Fig. 6
figure 6

UV absorbance spectra and Bandgap of lithium nickel vanadate nanoparticles

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$$\alpha h\upsilon =A{\left(h\upsilon -Eg\right)}^{n/2}$$
(7)

Here, α represents the absorption coefficient and hυ related to photon energy, Eg is material band gap, and A is constant. The band gap value of LiNiVO4 NPs was found to be 2.2 eV [12, 43], which is similar to the reported nickel orthovanadate such as Ni3V2O8 (2.25 eV) and NiV2O8 (2.29 eV) and is significantly narrower than the alkali earth orthovanadates such as Mg3V2O8(3.02 eV), Zn3V2O8 (2.92 eV), and FeVO4 (2.9 eV) (Table 3). This indicates that the substitution of Ni2+ significantly reduced the band gap of a compound, which is beneficial to the improvement of the photocatalytic activity.

Table 3 Comparison study of LNV NPs bandgap with other photocatalyst bandgap
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Applications

Photodegradation studies of LiNiVO4 nanoparticles

LiNiVO4 nanoparticles were exposed to visible light for the degradation of MB dye. Some energy absorbed by the nanoparticles is equal to or higher than bandgap energy. It forms the hole (h+) and electron (e−) on the surface of the photocatalyst. If the recombination rate of charge carriers is slow, they will start to move to the surface. Then, free electrons undergo reduction and form peroxides/superoxides. Water is oxidized by the hole and forms a hydroxyl radical. Further generated species act as strong oxidizing agents, and these radicals are highly reactive and unstable, finally leading to the degradation of methylene blue dyes/organic dyes. The organic dye is converted into CO2, H2O, and some other degradation products, as illustrated in Fig. 7. Photocatalytic activity of nanoparticles on dyes improved by several factors such as crystallinity, phase composition, particle size, structure, size distribution, and band gap. The photocatalytic activity of LNV1, LNV2, LNV3, and LNV4 nanoparticles is represented in Fig. 8. Among these nanoparticles, LiNiVO4 using 8 ml of fuel shows the highest percentage of degradation efficiency on methylene blue dye (Fig. 9). Based on this, we can conclude that LiNiVO4 nanoparticles using 8 ml jack fruit extract as a fuel are used to study the photocatalytic activity for the different parameters [44, 45]. The general mechanism of the photocatalytic activity of LiNiVO4 nanoparticles is proposed as follows.

Fig. 7
figure 7

General photocatalytic degradation mechanism of LiNiVO4 NPs synthesized by combustion method

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Fig. 8
figure 8

Photodegradation study of LNV nanoparticles with varied fuel

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Fig. 9
figure 9

UV–visible spectra of MB dye during degradation under visible light using LNV (1 to 4) nanoparticles

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$$LiNiV{O}_{4}+hv\to LiNiV{O}_{4}\left({{e}^{-}}_{CB}+{{h}^{+}}_{VB}\right)$$
(8)
$$LiNiV{O}_{4}+{h}^{+}\left(hole\right)\to \dot{}OH+{H}^{+}$$
(9)
$${OH}^{-}+{h}^{+}\to \dot{}OH\left(hydroxyl\; radical\right)$$
(10)
$${O}_{2}+{e}^{-}\to \dot{}{{O}_{2}}^{-}$$
(11)
$$Methylene\; blue+\dot{}HO+\dot{}{{O}_{2}}^{-}\to {CO}_{2}+{H}_{2}O+degradable\; products$$
(12)

The valence and conduction band (EVB, ECB) of the LiNiVO4 nanoparticles were theoretically calculated using the following expression.

$${E}_{CB}=\chi {\left({A}_{a}{B}_{b}{C}_{c}\right)}^{\left(1/a+b+c\right)}-{E}_{0}-0.5{E}_{g}$$
(13)
$${E}_{VB}={E}_{CB}+{E}_{g}$$
(14)

Here, χ is the absolute electronegativity, and a, b, and c are the number of atoms in the compound. E0 is the energy of free electrons on the hydrogen scale (4.5 eV). Eg is the band gap energy of nanoparticles. 5.514 eV is absolute electronegativity, and 2.2 eV is the band gap energy of lithium nickel vanadate nanoparticles. The theoretically calculated valence and conduction band values of LiNiVO4 NPs are 2.11 eV and − 0.036 eV, respectively.

Effect of different concentrations of catalytic load

Different concentrations of photocatalysts (10 to 70 mg) with constant dye concentration (5 ppm) of degradation are represented in Fig. 10. The percentage of degradation varied from 66.15 to 91.77%, and 50 mg of LiNiVO4 shows the highest percentage of degradation. When the catalyst load increases above 50 mg, the degradation percentage starts to decrease due to agglomeration and sedimentation of the catalyst. Also, the size of the particle increases the specific surface area decreases and leads to a decrease in surface active sites. So this concludes that 50 mg of LiNiVO4 nanoparticles shows the highest percentage degradation (91.77%) [45, 46].

Fig. 10
figure 10

Degradation of different concentrations of the catalyst under visible radiation

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Effect of dye concentration

Figure 11 indicates the photodegradation of LiNiVO4 nanoparticles with different concentrations of methylene blue dye. Here, 50 mg of catalyst is taken as constant with a different dye concentration of 5 to 20 ppm at pH-7. The percentage of degradation varies from 91.77 to 64.48% means the lowest concentration of dye (5ppm) shows the highest percentage of degradation [47, 48]. This is because as the dye concentration increases with decreases the penetration of light, it also decreases the active sites on the surface of LNV nanoparticles [32, 49, 50]. This leads to a decrease in degradation [51].

Fig. 11
figure 11

Variation of MB dye concentration versus irradiation time for LNV catalyst

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Effect of different pH on photodegradation

The degradation efficiency of LiNiVO4 nanoparticles on MB dye experiment at different pH was carried out by keeping the concentration of dye and catalyst constant (Fig. 12). It clearly shows that the degradation process mainly depends on the dye solution pH. Using 0.1 M NaOH or 0.1 M HNO3, the pH of the dye solution was adjusted [52]. The maximum degradation efficiency was observed in the basic medium than in the acidic medium. The pH 10 solution shows the highest percentage of degradation. Above this pH level, the degradation decreases because the surface absorbs negatively charged OH− ions and leads to a lowering of ˙OH radical production. Strong absorption of dye on the catalyst also decreases the percentage of degradation because it decreases the active sites of the photocatalyst to produce the hydroxyl radicals [55,56,57]. So the pH solution of 2 to 6 also decreases the percentage of degradation [56].

Fig. 12
figure 12

Percentage degradation of the effect of pH under visible light irradiation

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Scavenger activity on photodegradation

The photocatalytic activity in degradation is mainly due to the photoinduced species, charge separation, and surface redox process. The photocatalytic activity of nanoparticles in organic dye degradation can be increased by identifying the reactive species, which is mainly involved in breaking down the organic dye [57]. To investigate the reactive species which is involved in the photodegradation of methylene blue dye, several scavengers were used. The reactive species are trapped by scavengers and decrease their production. In this study, ethylenediamine tetraacetic acid (EDTA, 1 mM) [57], potassium dichromate (K2Cr2O7, 1 mM) [53], and sodium carbonate (NaCO3, 1 mM) [58] are used as a scavenger for h+ (hole), superoxide (O2−), and hydroxyl radicals (˙OH), respectively. Figure 13 reveals that the photodegradation of methylene blue dye without scavengers shows the maximum percentage of degradation. The presence of EDTA and Na2CO3 as scavengers decreases the photodegradation of MB dye and indicates that h+ and hydroxyl radicals are mainly involved in the degradation of MB dye. There is no significant degradation efficiency observed in the presence of the K2Cr2O7 scavenger. This reveals O2− radical is not significantly involved in the photodegradation of MB dye.

Fig. 13
figure 13

LiNiVO4 nanoparticles of photocatalytic activity on the MB dye degradation with different scavengers

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Recycling of catalyst

To determine the stability of LVN NPs, conduct a recycling experiment of MB dye degradation shown in Fig. 14. This experiment was carried out using 50 mg LNV catalyst with 100 ml 5 ppm dye. After completing each cycle, the LNV catalyst was washed with distilled water to remove dye residue. Figure 14 indicated that after the completion of 4 cycles, 80% of the dye was degraded by LNV NPs. This concluded the stability of the LNV NPs [59]. The XRD spectra of recovered LNV4 NPs are shown in Fig. 15. This confirmed the stability of LNV4 NPs and showed the same XRD peaks as the initial sample even after the fourth degradation cycle.

Fig. 14
figure 14

Recycling study of LVN NPs under visible light

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Fig. 15
figure 15

XRD spectra of recovered LNV4 NPs after completion of fourth cycle of degradation

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Table 4 describes the photodegradation behavior of some typical photocatalyst in the presence of LiNiVO photocatalyst. Among these photocatalysts, LiNiVO4 NPs are synthesized by simple, inexpensive, high yield, and energy-saving combustion method using green extract as fuel. Photocatalytic activity of LiNiVO4 NPs was analyzed using methylene blue dye. It is a common cationic dye and waste product from the textile industries. 91.77% of good degradation efficiency is shown by the LiNiVO4 under visible light illumination at 180 min.

Table 4 Comparison of photodegradation behavior of some typical photocatalysts and the present LiNiVO4 photocatalyst
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Electrochemical analysis

EIS spectra of synthesized LiNiVO4 NPs are shown in Fig. 16 in the form of a Nyquist plot. The impedance spectroscopy analysis plotted the frequency range between 1 Hz and 1 MHz. In the EIS graph, the semicircle curve represented a high-frequency region, and this corresponds to the charge transfer resistance (Rct) [67]. The next immediate line indicates the low-frequency region and explains the electrochemical reaction that occurs at the electrode controlled by diffusion and charge transfer process. The radius of the semicircle is directly proportional to the charge transfer resistance [68, 69]. Therefore, the smaller the semicircle radius, the higher the charge transfer resistance. The prepared LNVI, LNV2, LNV3, and LNV4 NP capacitance values were found to be 54, 53, 52, and 50, respectively. This data indicated that the LNV4 nanoparticle shows a lower arc radius than the other three nanoparticles. Table 5 shows fitted parameters and conductivity value of LNV NPs. This table explains as Rs value decreases as the conductivity value increases, and at the same time, the Cdl value increases as the charge transfer resistance value decreases. This concludes that LNV4 has good ionic conductivity and lower charge transfer resistance [54]. Figure 17 shows the angular frequency dependence of Z′ and Z″ of LNV4 NPs. Figure 17a shows the variation of the impedance’s real part (Z′) as a function of frequency. The decrease in Z′ magnitude at lower frequencies indicates the grain resistance reduction. Figure 17b shows the variation of Z″ with frequency.

Fig. 16
figure 16

Electrochemical impedance spectroscopy plot of different LNV nanoparticles

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Table 5 Summarized table for EIS fitted parameters of LNV NPs
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Fig. 17
figure 17

Frequency vs. Z′ (a) and Z″ (b) graph of LNV NPs

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Conclusion

This work provided a successfully synthesized lithium nickel vanadate photocatalyst by simple combustion method using jackfruit seed extract as fuel. The average crystalline size of the nanoparticle is 55 nm. Due to the narrow band gap (2.2 eV) of LNV NPs, exhibit its photocatalytic activity in the degradation of organic dye under visible light illumination. Hence, the inverse spinal structure of 50 mg of LNV4 NPs demonstrated efficient degradation under visible light irradiation for 180 min, achieving a degradation efficiency of 91.77%. The post-photocatalytic XRD analysis confirmed the chemical stability of the LNV NPs. Electrochemical impedance spectroscopy analysis revealed that LNV NPs were suitable for the supercapacitor preparation. The lower charge transfer and good ionic conductivity were shown by EIS analysis. This study successfully demonstrates that the simple and environmentally friendly synthesis of LiNiVO4 NPs using aqueous jackfruit seed extract and their promising characteristics make them a potential candidate for various environmentally and health-related applications such as photodegradation and electrochemical.