Showing papers on "Nafion published in 2022"

A Critical Review on the Use of Ionic Liquids in Proton Exchange Membrane Fuel Cells

Abstract: This work provides a comprehensive review on the incorporation of ionic liquid (ILs) into polymer blends and their utilization as proton exchanges membranes (PEM). Various conventional polymers that incorporate ILs are discussed, such as Nafion, poly (vinylidene fluoride), polybenzimidazole, sulfonated poly (ether ether ketone), and sulfonated polyimide. The methods of synthesis of IL/polymer composite membranes are summarized and the role of ionic liquids as electrolytes and structure directing agents in PEM fuel cells (PEMFCs) is presented. In addition, the obstacles that are reported to impede the development of commercial polymerized IL membranes are highlighted in this work. The paper concludes that the presence of certain ILs can increase the conductivity of the PEM, and consequently, enhance the performance of PEMFCs. Nevertheless, the leakage of ILs from composite membranes as well as the limited long-term thermal and mechanical stability are considered as the main challenges that limit the employment of IL/polymer composite membranes in PEMFCs, especially for high-temperature applications.

Recent developments in graphene and graphene oxide materials for polymer electrolyte membrane fuel cells applications

Abstract: 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.

A disposable and flexible electrochemical sensor for the sensitive detection of heavy metals based on a one-step laser-induced surface modification: A new strategy for the batch fabrication of sensors

Abstract: In this study, we developed a disposable and flexible electrochemical sensor for the sensitive determination of heavy metal ions based on an efficient one-step laser-induced surface modification. A flexible polyimide film was used as the substrate of the sensor, which was sprayed with a corresponding bismuth precursor ink to form a sensitive coating, i.e., bismuth nanoparticle@laser-induced graphene (BiNP@LIG). Then, Nafion was pipetted on BiNP@LIG to form a cover layer. The BiNP@LIG nanocomposite was successfully synthesized by laser irradiation (470 nm), and the composition of the obtained material was further verified by X-ray diffraction, energy dispersive spectroscopy and Raman spectroscopy. Moreover, the morphology of the BiNP@LIG nanocomposite was investigated by scanning electron microscopy, which showed that BiNPs were uniformly distributed on LIG, and the average diameter of the BiNPs was approximately 38 nm. Finally, a possible sensing mechanism of the Nafion/BiNP@LIG electrochemical sensor was proposed. The results show that the proposed electrochemical sensor exhibited satisfactory sensitivity and stability for the detection of Pb(II) and Cd(II). In addition, the laser-induced surface modification method proposed in this study could be an attractive candidate for the batch fabrication of sensors based on the noncontact, computer-controlled and pattern-making characteristics of laser induction.

High-Performance Electroreduction CO2 to Formate at Bi/Nafion Interface

Abstract: Electrochemical CO 2 conversion into valuable products provides a promising solution for achieving a carbon-neutral energy cycle. Herein, an active and stable Bi/Nafion interface is fabricated over Bi nanosheets with the modification of Nafion, which exhibits superior CO 2 conversion with formate selectivity of above 95% in a wide potential range, partial current density of 72.12 mA cm −2 at − 1.07 V vs. RHE in H-type cell. The extraordinary CO 2 reduction performance could be ascribed to a high CO 2 permeability and enhanced local proton activity at the Bi/Nafion interface, which leads to promoted CO 2 adsorption and feasible proton-coupled electron transfer during the CO 2 reduction process. Computational investigations reveal the modification of Nafion offers a comfortable platform to enable the key intermediate *OCHO to be stable. This work offers a valuable insight into interfacial manipulation of electrodes to convert CO 2 to valuable products. • An efficient strategy of a stable, active Bi/Nafion interface was proposed and realized by Nafion modification. • The Bi/Nafion interface exhibits the high performance of electrochemical CO 2 reduction to formate. • The Bi/Nafion interface shows promoted CO 2 adsorption and enhanced local proton activity. • Nafion acts as a protective layer to ensure the stability of the electrode.

Durability Testing of Low-Iridium PEM Water Electrolysis Membrane Electrode Assemblies

Abstract: Lowering the iridium loading at the anode of proton exchange membrane (PEM) water electrolyzers is crucial for the envisaged GW-scale deployment of PEM water electrolysis. Here, the durability of a novel iridium catalyst with a low iridium packing density, allowing for low iridium loadings without decreasing the electrode thickness, is being investigated in a 10-cell PEM water electrolyzer short stack. The anodes of the membrane electrode assemblies (MEAs) of the first five cells utilize a conventional iridium catalyst, at loadings that serve as benchmark for today’s industry standard (2 mgIr/cm2). The last five cells utilize the novel catalyst at 8-fold lower loadings (0.25 mgIr/cm2). The MEAs are based on Nafion® 117 and are tested for 3700 h by load cycling between 0.2 and 2.0 A/cm2, with weekly polarization curves and impedance diagnostics. For both catalysts, the performance degradation at low current densities is dominated by an increase of the overpotential for the oxygen evolution reaction (OER), whereby the OER mass activity of the novel catalyst remains ≈4-fold higher after 3700 h. The temporal evolution of the OER mass activities of the two catalysts will be analyzed in order to assess the suitability of the novel catalyst for industrial application.

Ultrahighly Sensitive QCM Humidity Sensor Based on Nafion/MoS2 Hybrid Thin Film

Abstract: In this article, a Nafion/MoS2 hybrid thin film was deposited on quartz crystal microbalance (QCM) for detecting humidity, in which moderate MoS2 nanosheets with small size were dispersed into a Nafion membrane to improve its humidity sensitivity. The experimental results indicate that a hybrid film QCM humidity sensor with the best volume ratio of Nafion/MoS2 exhibits a considerably higher shift frequency (−11 879 Hz) than a pure Nafion film QCM humidity sensor, even more than most of the reported QCM humidity sensors. It could be that the molybdenum disulfide nanosheets dispersed in the Nafion film would form some nano-assembly near the hydrophilic group of Nafion, which greatly enhances the ability of the composite film to establish water channels, thus promoting hydrophilicity of the composite film. The highly sensitive humidity sensor could clearly distinguish tiny humidity difference near the back and palm of a hand. Therefore, it has potential application in human–robot collaboration.