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A SO3H-functionalized graphene oxide-incorporated sulfonated poly (ether ether ketone) (S-GO/SPEEK) composite membrane was fabricated via the solution casting method, and the performance of the prepared membrane toward proton exchange membrane fuel cell (PEMFC) electricity generation was evaluated. Infrared spectroscopic measurements revealed the p...
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Although sulfonic acid (SA)-based proton-exchange membranes (PEMs) dominate fuel cell applications at low temperature, while sulfonation on polymers would strongly decay the mechanical stability limit the applicable at elevated temperatures due to the strong dependence of proton conduction of SA on water. For the purpose of bifunctionally improving...
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... Graphene has attracted considerable attention over the last decades because of its physicochemical properties, such as electronic conductivity, surface area, thermal/chemical stability, mechanical strength, and room temperature electron mobility [31,32]. The aforementioned properties of graphene are promising for versatile applications, such as batteries [33], refractive index sensors [34], sensors [35-39], solar cells [40], supercapacitors [41,42], and fuel cells [43]. The graphene oxide (GO) electrochemical reduction method is a fascinating approach because of the fast and environmentally friendly way to reduce GO synthesis, which is beneficial for electrochemical sensor applications [35][36][37]. ...
Regular water quality measurements are essential to the public water supply. Moreover, selective free chlorine (disinfectant) level monitoring without an interfering agent is necessary. The present work aimed to fabricate poly(caffeic acid) (p-CFA) coated on an electrochemically reduced graphene oxide (ERGO) surface for the selective detection of free chlorine. Electron microscopy and various spectroscopic techniques confirmed the p-CFA@ERGO/glassy carbon (GC) electrode. The p-CFA@ERGO/GC coated probe surface coverage was calculated to be 4.75 × 10-11 mol cm-2. The p-CFA@ERGO/GC showed superior catechol/o-quinone oxidation/reduction peaks for electrocatalytic free chlorine determination. The performance of the developed sensor electrode was outstanding, with an extensive range of free chlorine detection (20 mM to 20 mM), high sensitivity (0.0361 µA µM-1), and low detection limit (0.03 µM). The p-CFA@ERGO/GC capability of the realist water samples, such as the tested commercial and tap water, yielded a good range of recovery (from 98.5% to 99.9%). These values align with the standard N,N’-diethyl-p-phenylenediamine reagent method results.
... It was observed that the pristine SPEEK has a non-porous and smooth surface, while after the incorporation of nanoclays SPEEK membrane became significantly rougher. Also, the SPEEK membrane surface was covered by uniformly distributed white spots, indicating the confirmation of halloysite nanoclay and f-GO into SPEEK polymer [40,41]. The aluminium oxide and silicon oxide in the halloysite nanoclay and silane functionalized GO create the surface roughness and continuous transportation way for proton by incorporating halloysite nanoclay and f-GO into the polymeric membrane. ...
Membrane-based fuel cells, particularly methanol-based fuel cells, are thriving areas with high efficiency, less material consumption, and low emission of pollutants. But commercial membranes have less thermal withstanding ability and high cost, so alternative polymeric membranes have been developed with desired properties to overcome this issue. The SPEEK membrane was fabricated with halloysite nanoclay and functionalized graphene oxide (f-GO) nanocomposites at various concentrations via dry phase inversion. The sulfonic acid group in the SPEEK and silane functionalization of GO enhanced the Ion exchange capacity from 0.22 to 0.35 meq/g which enhances the proton conductivity. Furthermore, the thermal stability and hydrophilicity of the pristine SPEEK membrane were reformed with addition of halloysite nanoclay and f-GO in SPEEK membrane. The presence of nanocomposite on the surface of the SPEEK membranes was confirmed via scanning electron microscope (SEM) analysis. The 3 wt% halloysite nanoclay and 2 wt% of f-GO composite membrane was hold the 0.47 mS cm⁻¹ of proton conductivity and 72.2 mW cm⁻² of power density, whereas pristine SPEEK membrane was 0.31 mS cm⁻¹ and 28 mW cm⁻², respectively. The 3 wt% halloysite incorporated SPEEK membrane and 1.5 wt% f-GO incorporated SPEEK membrane was shown better proton conductivity, which act as a prominent membrane for direct methanol fuel cell (DMFC) applications.
... On the other hand, low DS can decrease the proton conductivity because of the unavailability of hopping sites. Hence, it is suggested that to maintain the DS value up to 65% in SPEEK [213]. The incorporation of different forms of graphene into SPEEK has exhibited remarkable properties and increased the performance of membranes. ...
Fuel cells are among the promising sources of clean energy, considering the low costs, low acoustical pollution, and the high-energy conversion. The remarkable features of graphene and its derivatives have triggered research studies on their applications in PEMFCs. PEMFCs still face some operational challenges for large-scale applications, including high costs, low proton conductivities at high temperatures, mechanical/thermal stabilities, and high fuel crossover. The unique characteristics of graphene-based materials, i.e., high electrochemical stability, good mechanical strength, large surface area, and excellent thermal stability, have been exploited in PEMFCs. This review discusses the potential role of graphene and graphene oxide (GO) in the membranes’ structural modifications, and utilization of polymer matrices such as SPEEK, PBI, PANI, SPAES, Nafion, and PVA polymers. The synthesis/functionalization of GO has been investigated with novel composite membranes and mechanisms involved in the enhancements of proton conductions, water uptakes, IECs, and power densities. Graphene materials showed excellent dispersion in solvents and alteration of membrane morphologies. The preceding properties are attributed to the formation of oxygen-based functional groups in GO nano-layers. The incorporation of graphene in other fuel cells, i.e., direct methanol fuel cells and biofuel cells, has exhibited commendable performance and appeared promising for commercial applications, especially with the reduction of fuel crossover.
... The prepared composite membrane resulted in higher water uptake and smaller swelling than Nafion's. The high proton conductivity of GO-g-SPEEK was attributed to the high water content confined in the composite membrane's nano-channels and the strong interactions between GO and SPEEK [108,126]. Under actual FC operation using 50% RH, the composite membrane exhibited a power output of 112 and 139 mWcm À2 at 25 and 60 C, respectively ( Fig. 4b and c). ...
Nafion membrane is a commercial type of electrolyte membrane that is widely used in low-temperature fuel cells. Nafion membrane is expensive and allows fuel to crossover from anode to cathode. Therefore, it decreases fuel utilization and results in mixed potential at the cathode. Modifying the Nafion membrane and/or replacing it with non-Nafion-based materials has shown promising results in solving these problems. Graphene is a two-dimensional material with exceptional properties that positively affect the performance of several energy conversion/storage devices. With its large surface functional groups, graphene oxide exhibits considerable ionic conductivity with low fuel crossover. This paper reviews and discusses the recent progress in utilizing graphene or its derivatives as a blend with Nafion and non-Nafion based membranes as well as a standalone membrane in low-temperature fuel cells. Graphene or its derivatives possess a high potential as a standalone membrane or a composite membrane in the various low temperature fuel cells applications in terms of high ionic conductivity at low humidity and relevant high temperature, high thermal, mechanical, and chemical stabilities. This work summarizes the recent progress in utilizing graphene and its derivatives (graphene oxide and other doped graphene) in different types of fuel cells, whether as a standalone or as a modifier of the Nafion and non-Nafion based membranes. The review covers the usage of graphene and its derivatives in PEMFCs, DMFCs, anion exchange DMFCs, and MFCs. Furthermore, it elaborates on the science and the engineering aspects of utilizing graphene and its derivatives in different fuel cells. This work demonstrates the importance of the graphene and its derivatives in improving the performance of low temperature fuel cells.
... The functionalisation of GO skeleton with acid groups, for example sulfonic ones (-SO 3 H) [9,[26][27][28][29][30] is considered an attractive approach to conveniently tune the features of this material. Sulfonated graphene oxide (SGO) is a promising candidate for PEMFC applications, as it fuses together GO strengths and an elevated concentration of oxygen-bearing moieties, amongst which sulfonic groups (-SO 3 H) provide a resemblance with the pendant chains of sulfonated ionomers. ...
... They own a strong acid behaviour in solution and an extreme solubility in water. These species should be more compatible with the GO framework by virtue of their bulky aromatic rings that can establish π-π interactions [34], differently from those described in literature, such as sulfanilic [26] and chlorosulfonic acid [27]. Amongst the analysed sulfonating agents, naphthalene sulfonate molecules have proven useful to mitigate dehydration issues at reduced humidity and elevated temperatures. ...
... The second one of about 20-35% occurs in the range 175-225 • C and it is associated to the decomposition of oxygenated functionalities (such as epoxides, tertiary alcohols and carboxylic acids) and to the release of CO x gases [55]. The third one is the smallest (2-5%) and it may be glimpsed between 280 and 300 • C. It can be ascribed to the decomposition of sulfonated moieties covalently bonded to NS compounds intercalated within GO flakes, as witnessed in ATR-FTIR spectra [27,56]. It can be intended as a qualitative proof of the reaction effectiveness, seeing as it is absent in typical GO thermograms (Fig. S2a) already discussed in a previous work amongst the authors' research group [41]; however, its limited value could mean a small quantity of inserted S-bearing groups. ...
This work presents a study on the preparation of novel self-assembling naphthalene sulfonate-functionalised graphene oxide membranes, whose analysis aims at assessing their potentiality as an alternative to perfluorinated proton conductors. Three different graphene oxide-to-naphthalene sulfonate molar ratios and two different process temperatures were combined to identify the most suitable conditions to perform an effective functionalisation. ATR-FTIR, Raman and EDX spectroscopies, thermogravimetric analysis, static contact angle evaluation and XRD aimed to point out the introduction of sulfonic acid groups (–SO3H) in the GO framework, while optical and scanning electron microscopies verified the good membrane uniformity. The evaluation of the ion exchange capacity (IEC) demonstrated the proton-exchanging ability of the prepared membranes. The most promising sample underwent water uptake (WU) and electrochemical impedance spectroscopy (EIS) tests to examine the dependence of its water sorption and proton conductivity with respect to relative humidity and temperature, in order to deepen the assessment of its feasibility as a possible future electrolyte in alternative energy generators. A preliminary investigation of the mechanical properties of the above-mentioned sample was performed as well to expand the characterisation of its behaviour.
... Therefore, improving the proton conductivity of SPAEKS with low DS is very desirable. 9 Doping functional inorganic materials to the polymer has been proved to be a promising approach to obtain PEMs with improved proton conduction performance. 10a In 2020, Sigwadi successfully fabricated Nafion R membrane blended with polyacrylonitrile nanofibers decorated with ZrO 2 and its proton conductivity could achieve 1.84 S⋅cm −1 at 25 • C. 10b Furthermore, ionic inorganic fillers can regular the hydrophilic channels and retain water in the SPAEKS matrix, facilitating the conduction of protons. ...
In the field of proton exchange membranes (PEMs), it is still a great challenge to explore new Nafion alternatives, maintaining the high proton conductivity and lowering the cost of practical application. In this work, a series of low sulfonated poly(aryl ether ketone sulfone) (SPAEKS) membranes hybridized by [Bi6O5(OH)3]2(NO3)10·6H2O (H6Bi12O16) have been successfully fabricated. When the doping amount of H6Bi12O16 reaches 5 wt%, the DS15‐Bi12‐5 showing the best proton conductive ability and mechanical properties. The proton conductivity can achieve 72.8 mS·cm−1 at 80°C and the tensile strength can reach 43.57 MPa. Confirmed by experimental data and activation energy (Ea) calculations, the existence of Bi cluster makes more hydrogen bonds, providing additional proton hopping sites and offers more proton transport vehicles, leading to a high proton conduction performance. This work proved that polyoxometalates (POMs) can replace the role of sulfonate groups in SPAEKS to a certain extent and work out the defects of high sulfonation, making a remarkable contribution to the practical application of low sulfonated SPAEKS. Combining the superiority of SPAEKS and POMs, a series of POM hybrid SPAEKS membranes were synthesized. The interaction between the host and guest solves the dissolution problem of the POMs and meanwhile the existence of Bi cluster makes more hydrogen bonds, providing additional proton hopping sites and offers more proton transport vehicles, leading to a high proton conduction performance.
... Yoo et al. reported improvement in the thermal and mechanical stability of composite membranes when GO was used as an inorganic nano-filler. In addition, the use of functionalized GO as a filler in the composite membrane resulted in excellent mechanical stability, fuel crossover prevention of membrane swelling, and improved ionic conductivity through π-π interactions with the polymer backbone [30]. ...
The development of potential and novel proton exchange membranes (PEMs) is imperative for the further commercialization of PEM fuel cells (PEMFCs). In this work, phosphotungstic acid (PWA) and graphene oxide (GO) were integrated into sulfonated poly(arylene ether) (SPAE) through a solution casting approach to create a potential composite membrane for PEMFC applications. Thermal stability of membranes was observed using thermogravimetric analysis (TGA), and the SPAE/GO/PWA membranes exhibited high thermal stability compared to pristine SPAE membranes, owing to the interaction between SPAEK, GO, and PWA. By using a scanning electron microscope (SEM) and atomic force microscope (AFM), we observed that GO and PWA were evenly distributed throughout the SPAE matrix. The SPAE/GO/PWA composite membrane comprising 0.7 wt% GO and 36 wt% PWA exhibited a maximum proton conductivity of 186.3 mS cm−1 at 90 °C under 100% relative humidity (RH). As a result, SPAE/GO/PWA composite membrane exhibited 193.3 mW cm−2 of the maximum power density at 70 °C under 100% RH in PEMFCs.
... Therefore, this composite material could be used as supporting materials in advanced areas, such as electronics, sensors, and fuel cells [20,35]. Also, recent studies have shown that the sulfonation of any organic material is known to increase proton transport, which promotes in fast electrochemical reaction [20,[36][37][38][39]. For this reason, to enhance the electrochemical performance, graphene oxide was sulfonated using a diazotization reaction. ...
... These sulfonic acid groups grafted GO-based composite have been utilised as an effective material because of the superior dispersibility of the catalyst on the SGO support [20,36]. The combining species of SGO and PAni can potentially increase the electrical conductivity along with the enhancement of effective specific surface area and provides more catalytic active sites of the composite catalyst [38,39]. To our best knowledge, the use of conductive polymer/sulphonated graphene oxide supported non-precious bimetallic nanoparticles as a cathodic catalyst in MFC has not yet been reported. ...
... FESEM is used to evaluate the morphological characteristics of different samples (Fig. 5). As shown in Fig. 5(a), GO reveals a thin sheet structure with crumpled, folded, and curved papers like morphology and this is consistent with earlier studies [39,40,[44][45][46]. After sulfonation, more wrinkled morphology was found on the surface of SGO sheets, signifying that the sheets were very thin. ...
This study examines the feasibility of the use of nanocomposite of polyaniline (PAni) grafted sulfonated graphene oxide (SGO) supported manganese cobalt oxide as a novel and effective cathode catalyst for single chamber microbial fuel cell (SC-MFC). The graphene oxide (GO) was sulfonated to SGO for the development of a significant increase in the hydrophilicity of GO to enhance the nano−catalyst dispersion. The structural properties of the prepared nanocomposite were studied by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. Morphological studies of the nanocomposite revealed a wrinkled paper−like structure of SGO and a spherical type structure of Mn−Co. Both cyclic voltammetry and electrochemical impedance spectroscopy showed a reduction current value of −1.04 mA, and charge-transfer resistance of 52.4 ohm, which exhibited a higher oxygen reduction reaction activity and good conductivity compared to Mn−Co/GO−PAni, Mn−Co/rGO−PAni and Pt/C catalyst. Electrochemical tests also suggest that the Mn−Co/SGO−PAni nanocomposite exhibited excellent durability among the other three cathodes. Furthermore, the MFCs equipped with Mn−Co/SGO−PAni nanocomposite modified electrode achieved power density of 1392.68 mW m⁻² which is 2.89 times higher than state-of-art Pt/C (481.3 mWm⁻²). The Electrochemical studies also displayed a similar result. The significant increase in power generation with Mn−Co/SGO−PAni nanocomposite as a cathode catalyst indicates that it can be used as a promising, inexpensive electrocatalyst for the long-term operation for MFC.
... graphene materials have been developed and reported [25,[42][43][44][45][46][47][48]. Some functionalized GOs were incorporated into PEMs as additives, and the resulting composite membranes showed significantly improved properties such as enhanced proton conductivity, thermal stability, ion selectivity, and mechanical properties [25,[49][50][51][52][53][54]. These kinds of composite membranes were presented as potential proton-exchange membrane replacements for industrial PEMFC applications. ...
... These kinds of composite membranes were presented as potential proton-exchange membrane replacements for industrial PEMFC applications. The sulfonic acid group is a commonly used functional group [25,[42][43][44][45][46][47][48]51,52,54], and the sulfonated GO (SG) can hold more water and, therefore, facilitates proton transportation [25,[49][50][51][52][53][54]. ...
... These kinds of composite membranes were presented as potential proton-exchange membrane replacements for industrial PEMFC applications. The sulfonic acid group is a commonly used functional group [25,[42][43][44][45][46][47][48]51,52,54], and the sulfonated GO (SG) can hold more water and, therefore, facilitates proton transportation [25,[49][50][51][52][53][54]. ...
In a proton-exchange membrane fuel cell, the proton-exchange membrane is located between the oxidant and the fuel, which facilitates proton conduction and prevents the penetration of gas molecules. In this study, sulfonated graphene oxides (SG) were synthesized, and a series of SG/Nafion composite multilayer membranes were prepared using layer-by-layer assembling. This multilayer membrane-structure has an efficient orientation effect on the SG sheets. The thinner the layer is, the more significant is the orientation effect. A statistical angle between the SG sheets and the membrane surface (Θ) is used to represent the orientation of SG sheets, and a correlation between the thickness of the layers and Θ is found. Under various conditions, these multilayer composite membranes improve the gas-barrier properties (H2, O2, and water vapor) and proton conductivity. The effect of Θ on the gas-barrier properties and proton conductivity of the membranes is discussed. Our results reveal that the SG sheets have excellent gas-barrier properties in the longitudinal direction and good proton conductivity in the lateral direction. Furthermore, based on positron-annihilation lifetime spectroscopy, it is found that the diffusion coefficients of gas molecules in all the SG/Nafion composite membranes are almost identical. In other words, the orientation of the SG sheets changes the gas-barrier properties of the membranes by altering the morphology of the diffusion paths for the gas molecules during the permeation.
... However, due to comparatively low proton conductivity of the additives in many cases the membrane conductivity is seriously hampered as the proton conducting groups in sPEEK membrane are considerably diluted. To minimize the adverse effects on membrane proton transport properties, various techniques are adopted to add different proton conducting functional groups to the fillers [6,[18][19][20][21][22][23][24]. ...
Sulfonated polyether ether ketone is currently under investigation to replace the expensive Nafion® as polymer electrolyte membrane. Sulfonic acid group is hydrophilic in nature and plays a key role in proton transfer in polymer electrolyte membranes. The higher the degree of sulfonation the higher proton conductivity in sPEEK based polymer exchange membrane is achieved; however, high degree of sulfonation causes severe dimensional instability due to higher water uptake which in turn affects membrane fuel retention capabilities as well as thermo-mechanical strength. Graphene oxide nanosheets were functionalized with aryl dizonium salt of p-Aminobenzene sulfonic acid for modification of sPEEK in low sulfonated state (DS = 53%) to improve its proton conductivity and suppress fuel crossover. The functionalization was carried out to compensate for the possible dilution of proton exchangeable sites by fillers. The resulting membranes were characterized in terms of morphology, thermo-mechanical behavior, methanol permeability, water uptake, and proton conductivities. The results proved that sulfonated GO not only improved thermo-mechanical behavior of the membrane but also dramatically increased proton conductivity (47 mS cm⁻¹) than pristine sPEEK (25 mS cm⁻¹). The composite membranes showed highly reduced methanol crossover compared with pristine sPEEK. The electrochemical selectivity increased from 9.5 × 10⁴ Scm⁻³s (pristine sPEEK) to 26.9 × 10⁴ Scm⁻³s.
