Introduction

Nowadays, energy storage or electrochemical device turns out to be the current attraction around the world where the development of energy devices enlightening the area of technology industry. Solar cell, supercapacitor, battery, fuel cell and monochromic device are the main example of energy device [1]. Electrolyte is identified one of the important components in the electrochemical device by operating the transference of ionic charges between electrolyte–electrode interfaces through the charge–discharge process; hence, the electricity will be conduct [2]. Liquid electrolytes (LE) were well known used in electrochemical devices due to good ionic conductivity [3]. However, there are problems reported using LE making it less suitable for energy device applications including harmful, leakage, poor electrochemical stability, high-cost and non-biodegradable [4, 5]. In order to overcome these drawbacks, solid biopolymer electrolyte has been studied widely. Biomaterials are one of the interests in the development of electrochemical devices as they are biodegradable and derived from renewable sources for promising performance.

Biomaterial is from natural resources, which are leakage-free, abundant in nature, low-cost production and good mechanical properties [6,7,8,9]. Many research has been conducted based on biopolymer for electrolytes application such as chitosan [10], carboxymethyl cellulose (CMC) [11], corn-starch [12], carrageenan [13], pectin [14] and agarose [15], and when doping with appropriate dopant, the conduction properties enhance in the ranging from 10−6 to 10−4 S cm−1. Alginate is another example of bio-polymer which suitable as an application for biopolymer electrolytes. In general, alginate is linear polysaccharides derived from a family of carbohydrates, which is origin of brown algae, and it is water soluble as a natural polymer [16,17,18]. The alginate was suitably used in polymer electrolytes due to the presence of carboxyl group, which could enhance the conduction performance. One of the alternatives in the electrochemical properties is via incorporation of dopant. In polymer electrolytes system, ionic dopant is dispersed in polymer backbone to generate ion conduction by acting as ionic charge carriers. Various types of ionic dopant have been thoroughly studied, including ammonium bromide (NH4Br) where it is classified as one of the charge carrier’s donors with excellent ability to donate proton (H+) and responsible for improving the ionic conduction of SBEs system [19,20,21].

It is an effort to reduce dependency on petrochemical-based electrolytes; therefore, this present work focuses on development of biopolymer namely alginate, which acts as host polymer and doped with ammonium bromide (NH4Br) as a possibility to become new type of polymer electrolytes system. The prepared sample was analyzed for structural and conduction properties by using Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical impedance spectroscopy (EIS), respectively.

Materials and methods

Materials

Biomaterial namely alginate (M.W. ~ 40,000) was obtained from Shaanxi Orient Co. and ammonium bromide, NH4Br (MW: 97.94 g mol−1) from Merck Co., respectively. In the present work, distilled water was used as solvent to dissolve alginate and NH4Br.

Sample preparation

2 g of alginate is dissolved in distilled water. Then, various amounts of NH4Br composition (5–30 wt. %) were added into alginate solution and stirred continuously until obtain a homogeneous mixture. The obtained mixture of alginate–NH4Br was poured into a petri dish and subjected in the oven (55 °C for 7 h) for drying process to obtain film form. The prepared samples were left in desiccator (with silica gel) for further drying in order to avoid any solvent trapped in the present sample. The designation of entire samples was tabulated in Table 1.

Table 1 Description of the alginate-NH4Br in SBE system
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Fourier transforms infrared spectroscopy (FTIR)

For the interaction analysis for alginate-NH4Br SBEs system, Fourier transform infrared (FTIR) spectroscopy using Perkin Elmer 100 spectroscopy was carried out using attenuated total reflection (ATR) accessory with germanium crystal. The sample was placed on germanium crystal, and infrared light was passed through the sample within the frequency from range 4000 to 700 cm−1 with resolution of 2 cm−1.

Thermal gravimetric analysis (TGA)

The thermal stability of the solid biopolymer electrolytes (SBEs) system was carried out by using Mettle Toledo TGA-DSC. The weight of sample was measured around ~ 2 mg and put into the silica crucible. The sample was heated up in range 30–800 °C with the heating rate of 10 °C min−1. The measurements were recorded in a nitrogen gas atmosphere at a flow rate of 20 ml min−1.

Differential scanning calorimetry (DSC)

The thermal properties of the prepared SBEs were determined by using NETZSCH DSC 214 polyma model where the prepared sample was sealed in an aluminum pan. The glass transition (Tg) of SBEs was analyzed at a heating rate of 10 °C min−1 in the temperature range from 30 to 300 °C under 40 mL min−1 flow of nitrogen inert atmosphere.

X-ray diffraction (XRD)

XRD profiles of alginate-NH4Br samples were recorded by using Rigaku MiniFlex II diffractometer at ambient temperature. The suitable size sample was adhered onto a sample holder. The spectra of XRD were scanned using CuKα (λ = 1.5406 Å) radiation in the Bragg angle 2θ range from 5° to 80°.

Scanning electron microscope (SEM)

The surface morphological analysis of the SBEs system at ambient temperature was investigated using FEI quanta 450 scanning electron microscope (SEM) with an accelerating voltage of 10 kV. SEM characterization was carried out at 2000- × magnification by using Everhart Thornley detector (ETD).

Electrical impedance spectroscopy (EIS)

Ionic conductivity of alginate-NH4Br SBEs system was characterized using impedance spectroscopy from HIOKI 3532-50 LCR Hi–Tester from ambient temperature to 353 K in the frequency range from 50 Hz to 1 MHz. The ionic conductivity, σ, of the film electrolyte was calculated using the following equation:

$$\sigma = \frac{b}{{R_{\text{b}} A}}$$
(1)

where b is the thickness of the electrolytes (cm), Rb is bulk resistance (Ω) and A is the electrode–electrolyte contact area (cm2).

Transport parameter analysis

The FTIR deconvolution approach is used in order to determine the free ions and transport properties of SBEs system using Origin Lab 8.0 software. Area under the peak was determined to enable the determination the free ions and contact ions (%), and hence, the percentage of ions could be calculated using the equation below [22]:

$${\text{Percentage }}\,{\text{of}}\,{\text{free}}\,{\text{ions }}\left( \% \right) = \frac{{A_{\text{f}} }}{{A_{\text{f}} + A_{\text{c}} }} \times 100\%$$
(2)

where Af is the area under the peak representing free ions region and Ac is the total area under the peak representing contact ions region. The number of mobile ions (η), ionic mobility (μ) and diffusion coefficient (D) of the SBEs system was calculated using equation [23]:

$$\eta = \frac{{MN_{\text{A}} }}{{V_{\text{Total}} }} \times {\text{free}}\,{\text{ions}} \left( \% \right)$$
(3)
$$\mu = \frac{\sigma }{\eta e}$$
(4)
$$D = \frac{KT\mu }{e}$$
(5)

In this work, M is the number moles for each weight percentage of NH4Br, NA is Avogadro’s number and Vtotal is the total volume of the alginate-NH4Br SBEs system, e is the electron charge, k is the Boltzmann constant and T is the absolute temperature in kelvin.

Results and discussion

FTIR analysis

Figure 1 depicts the optimization structure of pure alginate with empirical formula of C6H7O7 [24, 25]. According to Hema et al. [26], the cations of ammonium salts are expected to coordinate to polar groups of polymer matrix resulting in polymer-ammonium salts complexation. The complexation between alginate and NH4Br can be shown if any changes in intensity or wavenumber of FTIR spectra are observed. There is possible interaction of alginate at polar groups of carboxylate group (COO−), hydroxyl group (O–H) and glycoside bond (C–O–C). In Fig. 2, the FTIR spectra of pure alginate show that there are peak characteristics of 1043 cm−1, 1440 cm−1, 1652 cm−1, 3001 cm−1 and 3391 cm−1 which are attributed to glycoside bond (C–O–C), symmetric stretching of COO−, asymmetric stretching of COO−, polymer backbone structure of stretching CH2 and stretching OH group, respectively [27,28,29,30,31]. Meanwhile, for NH4Br, the twin stretching peaks at 3105 cm−1 and 3200 cm−1 correspond to N–H amine group and one absorption peak at 1420 cm−1 highlighted as ammonium ion (NH4+) functioning as free ions in SBEs system [6, 32, 33].

Fig. 1
figure 1

The optimized structure of pure alginate [3]

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Fig. 2
figure 2

The FTIR spectrum of pure alginate and NH4Br

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Figure 3 presents the FTIR spectra for various samples of SBEs system. The vibrational bands at 1043 cm−1, 1440 cm−1, 1625 cm−1 and 3391 cm−1 correspond to polar group of C–O–C, symmetric COO−, asymmetric COO− and –OH, respectively, which are existed in polymer matrix. Based on Fig. 3, the addition of 5 wt. % NH4Br dopant showed the shifted and increase in their intensity for absorption peaks from 1043 cm−1 to 1025 cm−1 which highlighted as C–O–C stretching vibrations and remain unchanged when added with 15 wt. % NH4Br. The shifted of IR peak at this band could be due to the migration of NH4+ cations toward C–O–C group in alginate [4]. The peak spectra at 20 wt. % NH4Br shifted further to 1029 cm−1 due to weak van der Waals attraction of dipole–dipole forces upon the increment of ionic dopant. The change of peak was affected by attraction of the ionic dopant to lone pair electrons of polymer when NH4Br was added in SBEs system [34, 35].

Fig. 3
figure 3

The FTIR spectrum of alginate-NH4Br in SBEs system

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Notably, the characteristic peak of un-doped sample at 1440 cm−1 and 1625 cm−1 correspond to symmetric COO− and asymmetric COO− are found to shifted to lower value at 1409 cm−1 and 1595 cm−1 when incorporated with NH4Br. In the present work, ion conduction is possible occurred based on Grotthuss mechanism due to the proton migration (H+) in polymer matrix [36]. This mechanism can be explained due to the coordination interaction of (COO−) moiety of alginate with H+ ion of [NH4+] substructure in NH4Br, which triggers the protonation between the cation (H+) and the carboxylate group of alginate via Grotthuss mechanism [37,38,39]. The increment of ionic dopant also leads to the increasing in peak intensity SBEs system from sample AlAB-1 to AlAB-6. In the present system, NH4+ cation moiety functioning as electrophile positive ion in NH4Br. There is tendency for the interaction between the coordinating site (oxygen) of carboxylate anion from alginate and the NH4+ via electrostatic attraction, which lead to the increase in ionic conductivity and electrochemical properties of SBEs system [1, 40]. It can be found there is decrement of peak intensity at 1595 cm−1 when introduce NH4Br more than 20 wt. %, and it is clearly can be seen for sample containing with 30 wt. %. This could be due to the phenomenon so-called salt aggregation where it is expected to decrease the mobility of ions which resulted to the decrement in ionic conductivity [41].

On the other hand, the broadband of pure alginate observed at 3391 cm−1 correspond to –OH group shifted to low absorption band at 3389 cm−1 upon addition of NH4Br. The addition of NH4Br leads to the shifting in wavenumber at –OH group indicating the presence of N–H stretching from NH4Br [42]. This trend is found to be similar as discovered by other researcher that using NH4Br as ionic dopant in SBEs system [43]. The schematic diagram showing their possible interaction between alginate and NH4Br is presented in Scheme 1 and changes of IR-band were summarized in Table 2.

Scheme 1
scheme 1

Schematic diagram of alginate having interacted with NH4Br salt via [N–H4+]

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Table 2 Summary of complexation between alginate and NH4Br in SBEs system
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TGA analysis

The thermal properties of alginate-NH4Br SBEs system were determined using thermal gravimetric analysis (TGA). Figure 4 depicts the thermograms for sample AlAB-0, AlAB-2, AlAB-4 and AlAB-6-based SBEs system. Three distinct decomposition stages were observed in temperature range of 30 °C until 800 °C under N2 atmosphere and were tabulated in Table 3.

Fig. 4
figure 4

TGA thermograms of alginate-NH4Br SBEs system

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Table 3 Thermal properties of SBEs system
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From Fig. 4, the first-stage decomposition in range 170–210 °C is related to losses of moisture content in SBEs system [44, 45]. The minimum weight loss was observed at AlAB-6 with 7.22% compared to un-doped sample (AlAB-0) with 14.09%. According to Ahmad and Isa [46], the temperature at range 50–200 °C attributable to evaporation and degradation process of water and residual solvent inside polymer electrolyte film. The second-stage decomposition was contributed to the loss of carboxylate group (COO−) from the polymer backbone. The pure alginate (AlAB-0) exhibits weight loss about 36.29% with decomposed temperature 270 °C. According to Swamy and Ramaraj [47], the alginate consists major structure of carboxylate group in polymer matrix and easily to undergo decarboxylation (degradation) at range 219–261 °C. However, addition of ionic dopant into polymer backbone attributed to dissociation easily upon heating process where more protonation of cation (H+) from NH4Br to COO− of alginate backbone as discussed in FTIR analysis; hence, the decomposed temperature increased and the weight loss of SBEs system reduced. The decrement of weight loss in AlAB-4 with 34.12% were expected strong amorphous phase in the structure, which enhance the heat sensitivity of SBEs system. This suggesting the enhancement of thermal stability where less monomer detached from polymer backbone due to complexation of alginate-NH4Br in SBEs system [37].

A small reduction of weight loss was observed at last stage of decomposition in range between 280 and 650 °C. AlAB-4 showed minimal value of weight loss 4.57% at temperature 560 °C. Cheong and Zhitomirsky [48] and Huq [49] reported in their work there are degradation and burning out of remaining carbon from alginate polymer when reached ~ 500 °C. The increment of temperature above decomposed temperature 650 °C (prolong heating) resulting the carbonization of polymer backbone into ash formation [50, 51]. From TGA analysis, alginate polymer is suitable used as host in electrochemical devices due to thermal stability in SBEs system.

DSC analysis

Differential scanning calorimetry (DSC) was used to characterize the thermal behavior of materials, which can further confirm the presence of miscibility between alginate and NH4Br by measures the change in the heat capacity as the polymer matrix goes from the glass state to rubber state as known as Tg [52, 53]. DSC thermograms of the various alginate-NH4Br SBEs samples were presented in Fig. 5, and the glass transition temperatures (Tg) are depicted by arrows as shown in figure. From Fig. 5a, the Tg for AlAB-0 was not detected at this range of temperature study. However, the exothermic peaks were founded at 180 °C indicates the further process of degradation. According to Báez et al. [54] and Soazo et al. [55], the exothermic peaks observed at temperatures between 170 and 250 °C result from degradation of alginate due to dehydration and depolymerization of the protonated carboxylic groups and oxidation reactions of the macromolecule.

Fig. 5
figure 5

DSC thermograms of a AlAB-0, b AlAB-2, c AlAB-4 and d AlAB-6 SBEs system

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In SBEs system, the Tg value was clearly observed, and the observed Tg depends on the dopant composition. The incorporation of 10 wt. % of NH4Br to alginate polymer matrix showed the initial Tg value at 77.52 °C due to the formation of coordination between the polymer chain segments and ions formation from ionic dopant which increases the energy barrier to the segmental motion of the polymer chains; thus, the stiffening of the polymer chains may occur [56]. Notably, the addition of 20 wt. % of NH4Br (AlAB-4) causes the Tg to shift to lower temperature, thus, it helps soften the polymer chain backbone, and this similarly been observed by other research work [57]. The decrease in Tg indicates an increase in the flexibility of alginate chains; hence, the AlAB-4 was expected to exhibit highest ionic conductivity value [4]. Further increase in the composition of NH4Br leads to the increment of Tg value. It can be attributed to the formation of ion aggregates in alginate polymer matrix, which reduced the flexibility of the polymer chain [58]. A similar trend has been observed by Moniha et al. [59] for the system based on iota carrageenan complexed with ammonium thiocyanate (NH4SCN).

XRD analysis

Figure 6 depicts the XRD patterns from various NH4Br compositions doped with alginate as a SBEs system. For un-doped (AlAB-0) sample, it can be observed that there are two principal diffraction peaks at 13.84° and 23.18° revealed the semi-crystalline structure as reported by other works [60, 61]. According to Yang et al. [62] and Zhang et al. [63], the pure alginate showed two broad amorphous peaks attributed to typical polysaccharides which as similarly observed in the present system for the un-doped (AlAB-0) sample.

Fig. 6
figure 6

X-ray diffractogram of all alginate-NH4Br SBEs system

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As stated by Hodge et al. [64,65,66] criterion, the amorphous nature of polymer matrix can be established by a correlation between the height of the peak intensity and degree of crystallinity. It clearly can be seen that the addition of NH4Br reducing the intensity of broad peak and shifted to higher angle from sample AlAB-1 until AlAB-4. Disappearance of sharp peaks inferred that the dopant systems are completely dissociate in the polymer matrix [13]. This indicates there are complexation occur between NH4Br and alginate polymer resulting in increment of amorphous hump [36]. The maximum amorphous nature of polymer membrane eases the protonation of H+ to the alginate backbone by imparts more oxygen vacant site and thereby improve the ionic conductivity to the greater extent [67,68,69]. Based on XRD results, it shown that the AlAB-4 sample exhibits good amorphous in nature and no noticeable peaks founded in system which expected to achieve higher ionic conductivity. However, the amorphous phase of SBEs system starts to decrease at sample AlAB-5, and this might be due to incapable of host polymer (alginate) to accommodate the NH4Br which leads to decrease in transport properties values and ionic conductivity [70, 71].

SEM analysis

Scanning electron microscopy (SEM) was carried out for extensive morphological inspection of cross section in alginate-NH4Br SBEs film. The surface morphology for SBEs system with the magnification of 2000 times and range 50 µm was depicted in Fig. 7. From the SEM image of alginate film (AlAB-0), it was found that the structure was smooth surface with no phase separation, suggesting no susceptible filling [72].

Fig. 7
figure 7

Surface micrographs for a AlAB-0, b AlAB-2, c AlAB-4 and d AlAB-6 of alginate-NH4Br SBEs system

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In the SBEs system, AlAB-2 showed no differences in the surface properties implying that the samples are homogeneous and amorphous nature. Due to the complete dissolution of salt in polymer matrix, the enhancement of segmental motion takes place in the polymer electrolyte. Such segmental motion produces empty spaces, which enables the easy flow of ions in the material in the presence of electric field, and it expected increases the ionic conductivity [73]. Upon addition of salt until sample AlAB-4, the SEM image showed the homogeneity rough surface without any phase separation that could be due to the ion set-ups in the polymer electrolyte which enhanced the transport of protonation [74]. However, addition 30 wt% of NH4Br into the alginate led to the formation of salt agglomeration. The results shown that the morphology of samples were found to aligned with XRD analysis where it might be formed by less dissolution of salt in the polymer matrix.

Conductivity analysis

Figure 8 depicts ionic conductivity value for various compositions of NH4Br SBEs system at ambient temperature (303 K). The conductivity value for un-doped (AlAB-0) sample was observed to be 4.67 × 10−7 S cm−1. It can be clearly seen that the ionic conductivity begins to increase when 5 wt. % of NH4Br was added and achieved to the optimum value at 4.41 × 10−5 S cm−1 for sample AlAB-04. The enhancement of ionic conductivity to the higher value could be attributed to the increment in amorphous phase in SBEs system as observed from XRD analysis, thus, large amount of H+ can migrate toward the coordinating site in biopolymer host with lesser of blocking pathway [75, 76]. According to Rasali and Samsudin [77], the increment of ionic conductivity proved the increasing number of mobile ions that led to interaction between salt and polymer matrix via Grotthuss mechanism. However, the addition of salt beyond 20 wt. % depicts the decrement of ionic conductivity in SBEs system. This attributes to the re-crystallization of polymer matrix where packed with ions (salt aggregation) as demonstrated in XRD and SEM analysis; thus leads to the enhancement of energy barriers to segmental motion in SBEs system [78].

Fig. 8
figure 8

Ionic conductivity and activation energy for alginate-NH4Br SBEs system at ambient temperature

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The temperature-dependence study of ionic conductivity for various alginate-NH4Br SBEs at different temperature range from 303 to 353 K was presented in Fig. 9. In this study, it can be observed that the ionic conductivity of SBEs system increased with temperature, and this indicates that the polymer electrolyte is thermally activated [79]. This can be proved as revealed by TGA analysis where the polymer backbone (alginate) has been improvised with addition of NH4Br in alginate and led to expansion of biopolymer matrix to provided free volume where the ions easily to migrate, thus resulting in increment of conductivity value [80, 81]. All SBEs system obeys the Arrhenius behavior where regression value, R2 close to unity (R2 ~ 1) [82, 83]. The activation energy (Ea) for the SBEs system has been calculated by the linear fitting of the Arrhenius equation [84, 85].

$$\sigma = \sigma_{0} \exp \left( { - \frac{{E_{\text{a}} }}{kT}} \right)$$
(6)

where is a σ0 pre-exponential factor, Ea is the activation energy of electrical conduction, k is the Boltzmann constant and T is the temperature in Kelvin. From Fig. 8, it can be seen that the activation energy reduces as the ionic conductivity increases. The highest conducting sample (AlAB-4) with conductivity 4.41 × 10−5 S cm−1 exhibits lowest activation energy of 0.2382 eV. This phenomenon generates faster rate of H+ motion in polymer chain where it leads to enhancement of amorphous phase and higher in ionic conductivity for the present SBEs system [86]. Therefore, the H+ ions required less energy to migrate to coordinating site of polymer matrix [87].

Fig. 9
figure 9

Ionic conductivity of alginate-NH4Br SBEs system at selected temperature

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Transport analysis

In the present system, the transport parameter was determined using FTIR deconvolution technique, which is favorable method [88,89,90]. FTIR deconvolution for sample AlAB-3, AlAB-4 and AlAB-6 of SBEs system was presented in Fig. 10. The range of wavenumber between 1300 cm−1 and 1500 cm−1 is selected due to the most significant changes of IR-band peak and wavenumber as shown from FTIR analysis. The peaks at ~ 1410 cm−1 are assigned as free ions and peaks at ~ 1400 cm−1 and ~ 1463 cm−1 assigned as contact ion pairs and formation ion aggregates, respectively [91, 92]. Based on deconvolution approach, the percentage of free ions and contact ions was calculated using Eq. 2 and tabulated in Table 4. It can be observed that the free ions increase with addition of NH4Br until reached sample AlAB-4. This attributes to increment of ion dissociation from NH4+ to polymer matrix; thus, it directly increases the conductivity value of SBEs system [36], whereas at AlAB-5, the free ions start to decrease slightly which is due to the re-association of ions, therefore lead to the formation of ion cluster and the decrement of amorphous phase (as shown in XRD and SEM analysis) [90, 93].

Fig. 10
figure 10

FTIR deconvolution for sample a AlAB-3 b AlAB-4 and c AlAB-6 SBEs system

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Table 4 Transport properties of alginate-NH4Br SBEs system
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Based on the parameters in Table 4, number of mobile ions, (η), ionic mobility (μ) and diffusion coefficient (D) were calculated. It is clearly can be seen that the number of mobile ions increased linearly with addition of NH4Br; meanwhile the ionic mobility and diffusion coefficient followed the conductivity pattern where the highest μ and D for AlAB-4 is 1.37 × 10−9 cm2 V−1 s−1 and 3.58 × 10−11 cm2 s−1, respectively. Similar pattern was reported by Ramlli and Isa [89] where the ionic mobility (μ) and diffusion coefficient (D) were governed by ionic conductivity in their polymer electrolyte system. The continuous increment of η with addition of NH4Br exhibits the over crowd of H+ ions which lead to formation of ion cluster [94]. Therefore, ions migration requires higher activation energy, Ea to undergo protonation process; thus, the μ, D and ionic conductivity value start to reduce rapidly in SBEs system [23]. The increase in ionic dopant altered the dipole interaction of H+ ions in alginate-NH4Br complexes and promoted the re-crystallization structure as proven by XRD analysis [36].

Conclusion

In the present work, solid biopolymer electrolytes (SBEs) system based on alginate polymer doped with various compositions of ionic dopant NH4Br was prepared via solution casting technique. The complexation between alginate and NH4Br was investigated by using FTIR analysis where there are significant possible interaction happen at C–O–C stretching, symmetric and asymmetric COO− stretching and OH− stretching. There is strong contribution of hydrogen bonding from protonation H+ to COO− moiety of alginate polymer. The TGA and DSC analysis shown the SBEs system promoted good thermal stability where also improved their amorphous phase as revealed by XRD and SEM analysis. The highest ionic conductivity at ambient temperature was observed for sample AlAB-4 with 4.41 × 10−5 S cm−1. The temperature-dependence ionic conductivity of present all SBEs system obey the Arrhenius behavior where the regression value, R2 close to unity (R2 ~ 1) and thermally assisted. The ionic conductivity of alginate-NH4Br SBEs system was found to be governed by the ionic mobility (μ) and diffusion coefficient (D). From the results obtained, it shown that the present SBEs system-based alginate-NH4Br has the possible potential to be applied for electrochemical applications.