One-step formation of ultra-thin chemically functionalized redox-active Langmuir–Schaefer Nafion films

Abstract

A novel ''one-step procedure'' to incorporate different cationic redox-active species within ultrathin Nafion films is reported. Ultra-thin films of Nafion containing trimethylammonioferrocene (FA + ), tris(2,29-bipyridyl)ruthenium(II), Ru(bpy) 3 2+ , and hexaaminoruthenium(III),[Ru(NH 3 ) 6 ] 3+ , were prepared using the Langmuir-Schaefer (LS) technique. The morphology and thickness of the films were evaluated with atomic force microscopy (AFM). Film thicknesses were 1.9 ¡ 0.7, 1.8 ¡ 0.9, 1.5 ¡ 0.9 nm per layer for Nafion-FA + , Nafion-Ru(bpy) 3 2+ and Nafion-[Ru(NH 3 ) 6 ] 3+ , respectively. Electrochemical data confirmed the successful incorporation of the mediators into the films and proved that the redox activity was maintained during extensive voltammetric cycling. Key parameters such as surface coverage, concentration of the mediator within the films and apparent diffusion coefficients were extracted using cyclic voltammetry. To demonstrate the utility of the redox-active films for sensing applications, films with Ru(bpy) 3 2+ incorporated were utilized for the electrocatalysis of oxalate in aqueous solution. Experimental MaterialsNafion 117 solution (5% w/v mixture of low molecular weight alcohols) and NaCl were purchased from Sigma-Aldrich.

Incorporation of Functionalized Palladium Nanoparticles within Ultrathin Nafion Films: A Nanostructured Composite for Electrolytic and Redox‐Mediated Hydrogen Evolution

“…[1] Among polymer membranes, Nafion, a perfluorinated ion-exchange polymer containing tetrafluoroethylene and perfluorovinyl ether units, terminated with a -SO 3 H group, is probably the most common polymer electrolyte used in PEFCs and DMFCs because of its good thermal and chemical stability, together with high proton conductivity. [2][3][4][5][6] These properties are further expanded through the ability of Nafion to preconcentrate cationic species, making it possible to host a wide range of entities such as redox mediators [7][8][9][10][11][12][13][14] and nanoparticles [15][16][17][18][19][20] for different types of catalytic applications. [21,22] An important factor limiting the practical development of DMFCs is methanol crossover from the anode to the cathode through the polymer membrane; this causes significant loss of fuel and concomitant poisoning of the catalyst at the cathode side.…”

Facile Fabrication of Solid‐state Electrochemiluminescence Sensor via Non‐covalent π‐π Stacking and Covalent Bonding on Graphite Electrode

“…S1). The results showed that both the anodic ( i pa ) and cathodic ( i pc ) peak currents were proportional to scan rate ( v ), which indicated that the reversible redox reaction of the immobilized ruthenium complex on the Ru‐pyrene‐GE sensor underwent a surface controlled process 30. The interference study (Fig.…”

Ionomer Thin Films in PEM Fuel Cells

“…Recent years have witnessed a significant effort dedicated toward understanding PFSA thin films, which exhibit reduced transport properties compared to those of bulk films due to abovementioned confinement effects [1,20,27,32,33,36,37,[53][54][55][56][57][62][63][64][65]. Compared to bulk membrane, Nafion ® films of~100 nm or thinner have been shown to exhibit reduced swelling [20,27,33,66,67], water uptake amounts and rates [20,24,27,32,33,36,54,56,57,64,65,68], reduced ionic conductivity and increased activation energy [5,34,36,37,53,56,64,69,70], lower rate of water diffusion [27,54,65,68,71,7...…”

“…Hence, there exists a strong interplay between the film's morphology and transport phenomena, as dictated by confinement and interactions, whether it is in contact with air or a substrate [8,14,20,34,53,55,67,68]. When confined to thin films, PFSA exhibits not only lower diffusion [27,54,65,68,71,72] but also a few orders of magnitude slower relaxation, indicating more restricted chain dynamics [68]. An important implication of confinement effect for fuel cell ionomers is the reduced conductivity with decrease in film thickness [5,34,36,37,53,64,70,91] and exhibits a substrate dependence [34] ( Fig.…”