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Solid Polymer Electrolyte Membranes
Published in Asit Baran Samui, Smart Polymers, 2022
Swati S. Rao, Manoranjan Patri
It is interesting to note that the polymer morphology plays a significant role in the ion-conducting properties of the membranes. Nafion® is known to possess very high ionic conductivity due to the phase separation of the hydrophilic and hydrophobic regions of the polymer backbone and ionic groups. Ionic clusters are formed within the polymer membrane, when swollen in water, which are interconnected and function as proton-conducting pathways or channels. These channels swell or shrink depending on the amount of “free” water present within the clusters. Hydrocarbon-based membranes exhibit lower conductivities when compared to Nafion®, due to poor water channel formation because of weak phase separation between hydrophobic and hydrophilic moieties. Further, the dependence of conductivity on the humidity lowers the operational temperature and increases the system complexity. The introduction of non-volatile liquids, such as ionic liquids or phosphoric acid as proton conductors, promotes the transport of protons by the Grotthuss mechanism. This enables the fuel cell to be operated at higher temperatures and under dry conditions. Also, in order to compensate for the loss in conductivity due to structural limitations, inorganic nano-materials have been introduced into the membrane matrix. These materials, if ionic in nature, can create proton-conducting pathways for improved performance.
Nanobiosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
Lyons and Keeley (2008) studied carbon nanotube-based modified electrode biosensors. Among electrochemical biosensors based on enzyme attachment, the glucose oxidase (GOx) assemblies are unquestionably the most deeply studied system. This enzyme has attractive characteristics, such as its well-known behavior, great stability, and robustness. Comparison of the voltammograms obtained using a bare, SWCNT-modified, and SWCNT/GOx and SWCNT/GOx/Nafion-modified GC working electrodes in a 50 mM phosphate buffer (pH = 7) revealed that a bare GC electrode exhibited a virtually flat and uninspired, featureless voltammetric response, whereas a pair of well-defined redox peaks were observed at the both the SWCNT/GOx and SWCNT/GOx/Nafion-modified electrodes. Nafion (C7HF13O5S·C2F4) is a commercial sulfonated tetrafluoroethylene-based fluoropolymer-copolymer.
Development of Alternative Proton Exchange Membranes Based on Biopolymers for Microbial Fuel Cell Applications
Published in Lakhveer Singh, Durga Madhab Mahapatra, Waste to Sustainable Energy, 2019
Srinivasa R. Popuri, Alex J.T. Harewood, Ching.-Hwa Lee, Shima L. Holder
Nafion is the widely used proton exchange membrane in fuel cell technology due to its advantages of proton conducting ability and high physical (mechanical and structural) and chemical stability (Devanathan 2008). In fact, most of the commercial PEMs are developed using perfluorosulfonic acid (PFSA) polymer membranes, such as Acipex®, Flemion®, and Nafion®. Walther Grot of DuPont discovered Nafion® membrane in 1970 and it consists of a hydrophobic –CF2–CF2– fluorocarbon backbone with hydrophilic sulfonate groups (SO3H−) (Oh and Logan 2006, Jana et al. 2010, Liu et al. 2016). However, Nafion membranes have two significant issues yet to be resolved, i.e., they are expensive to produce (Hernandez-Flores 2014, Shahgaldi et al. 2014) and permit methanol crossover. In addition, Nafion could not be ideal for MFC at neutral or higher pH, because other cations are dominant in moving from anode to cathode compared to protons (Rozendal et al. 2006).
The effect of VOC and environmental parameters on ozone sensors performance
Published in Advances in Building Energy Research, 2023
Mahsa Ghasemi, Fariborz Haghighat, Chang-Seo Lee, Marzieh Namdari
Permeability of interfering compounds in the Nafion tube installed in 211-2B is another factor that should be considered. Nafion is a copolymer, which consists of a tetrafluoroethylene backbone with sulphonic acid groups. The presence of sulphonic acid in the Nafion structure makes it selectively permeable to compounds that bind to sulphonic acids such as water, alcohol and ammonia (Korotcenkov et al., 2018; Wei et al., 2018). The results of various studies indicated that some polar compounds, such as alcohols, aldehydes, ketones and water-soluble esters, permeate through the Nafion dryer similar to water vapour (Felix et al., 2016; Prajesh et al., 2019; Rai et al., 2017). Based on the EPA report, certain polar VOCs (amines, ketones, alcohols and some ethers) are lost when humidity is removed by a Nafion dryer (Barro et al., 2009; Felix et al., 2016; Karnati et al., 2019). It can be concluded that the 211-2B response did not change at 50% RH by injection of acetone (it is a ketone) due to its solubility in water and its permeation in the Nafion tube. Toluene is an aromatic compound, which is not removed by the Nafion tube because of having a benzene ring. That is the reason its outputs in humid condition were affected upon injection of toluene. Ethanol belongs to the alcohol group and it can be removed by Nafion tube, but this compound slightly affected 211-2B responses in humid condition due to the reason explained above.
Performance of Paracoccus homiensis DRR-3 in microbial fuel cell with membranes
Published in International Journal of Ambient Energy, 2018
Deepika Jothinathan, Richard Thilagaraj Wilson
Thus, PEM is one of the main components that contributes to the power output. The Nafion 117 membrane (Dupont Co., USA) is one of the most commonly used PEMs in the MFC for the proton transfer. Nafion is a sulphonated tetrafluorethylene copolymer with a (CF2–CF2) backbone and sulphonate groups attached to it (Mauritz and Moore 2004). However, there are limitations such as biofouling, leakage of oxygen, substrate loss and so on (Logan et al. 2006).
A novel amperometric bienzymatic biosensor based on alcohol oxidase coupled PVC reaction cell and nanomaterials modified working electrode for rapid quantification of alcohol
Published in Preparative Biochemistry and Biotechnology, 2018
Vinita Hooda, Vikas Kumar, Anjum Gahlaut, Vikas Hooda
During the past years, owing to their excellent mechanical, electronic, thermal and optical properties, nanoparticles have been widely employed in the fabrication of next generation biosensors to improve important performance indexes such as sensitivity, stability, and repeatability. c-MWCNTs offer exceptionally high electroactive surface (due to its material properties such as electrical and thermal conductivity) for rapid exchange of electrons between the electrode and the enzyme.[22] AgNPs and carbon nanotubes display strong electrical properties and high surface to volume ratio which makes them capable of increasing the enzyme loading onto the surface of electrode for amplifying the sensor signal. Chitosan is a significant biopolymer, which has been gradually used for fabricating sensors owing to its high mechanical strength, easy availability, exceptional film-forming ability, non-toxicity, high permeability, low cost, and easy to modify with the help of chemicals.[23] Due to the hydrophilic nature of chitosan, it also facilitates the rate of electron transfer after its swelling in reaction mixture. Nafion is a sulfonated tetrafluorethylene copolymer that has been extensively utilized in the biosensor applications.[24] Biocompatibility, mechanical strength, excellent thermal stability, and antifouling properties of Nafion, makes its use advantageous in biosensor applications. Nafion is an effective solubilizing agent for carbon nanotubes (CNTs) that resulted in fabrication of CNT-based biosensors exhibiting both the antifouling properties of Nafion films as well as the efficient electrocatalytic action of CNT toward H2O2.[25] Immense potentiality of enzymes, carbon nanotubes, and nanoparticles has boosted scientific enthusiasm towards fabrication of alcohol biosensors with excellent sensitivity, which is an ever-lasting goal in the field of health area for commercial successes.