Self-assembled films from chitosan and poly(vinyl sulfonic acid) on Nafion® for direct methanol fuel cell

Abstract

Filmes de quitosana/poli(ácido vinilsulfônico) (PVS) foram depositados sobre membranas de Nafion ® a partir do método camada por camada (LbL), visando o seu uso em células a combustível de metanol direto (DMFC). Métodos computacionais e espectros de infravermelho com transformada de Fourier (FTIR) sugerem a formação de um par iônico entre o grupo sulfônico do PVS e o grupo amino protonado da quitosana, o qual promove o crescimento dos filmes LbL sobre a membrana de Nafion ® , assim como impede parcialmente a passagem de metanol. Experimentos de cronopotenciometria e varredura linear de potencial foram realizados a fim de se investigar a passagem de metanol através das membranas de Nafion ® e quitosana/PVS/Nafion ® em uma célula a diafragma. Os valores de resistência iônica associada ao transporte de prótons nas membranas de Nafion ® e quitosana/PVS/Nafion ® são próximos, de acordo com as medidas de impedância elétrica devido à pequena espessura do filme LbL. Assim, espera-se um melhor desempenho da DMFC, uma vez que a resistência do filme automontado é insignificante comparada ao resultado associado à passagem de metanol através das membranas.Chitosan/poly(vinyl sulfonic acid) (PVS) films have been prepared on Nafion ® membranes by the layer-by-layer (LbL) method for use in direct methanol fuel cell (DMFC). Computational methods and Fourier transform infrared (FTIR) spectra suggest that an ionic pair is formed between the sulfonic group of PVS and the protonated amine group of chitosan, thereby promoting the growth of LbL films on the Nafion ® membrane as well as partial blocking of methanol. Chronopotentiometry and potential linear scanning experiments have been carried out for investigation of methanol crossover through the Nafion ® and chitosan/PVS/Nafion ® membranes in a diaphragm diffusion cell. On the basis of electrical impedance measurements, the values of proton resistance of the Nafion ® and chitosan/PVS/Nafion ® membranes are close due to the small thickness of the LbL film. Thus, it is expected an improved DMFC performance once the additional resistance of the self-assembled film is negligible compared to the result associated with the decrease in the crossover effect.Keywords: chitosan, direct methanol fuel cell, proton exchange membrane, crossover effect, methanol permeability IntroductionDirect methanol fuel cells (DMFCs) are the most promising portable, stationary power sources with application in several fields. In these cells, methanol and air are continually injected into the anode and cathode compartments, respectively, thus providing energy with high efficiency. Methanol has been largely employed as fuel once it is abundant and inexpensive. Even though DMFCs produce carbon dioxide, which is released into the atmosphere, their high efficiency guarantees low pollution as compared to other power sources. [1][2][3] One drawback of DMFCs is the so-called crossover effect, through which methanol leaves the anodic compartment and crosses the proton exchange membrane (PEM), thereby promoting cell de...

Amperometric Detection of Lactose Using β-Galactosidase Immobilized in Layer-by-Layer Films

“…The main bands for (PEI/PVS) 3 LbL films in Figure appear at 1040, 1195, 1412, and 1573 cm –1 , assigned to the symmetric and asymmetric stretching of SO groups, angular deformations of CH (bending) in the polymer chains, and angular deformation of NH groups, respectively. − Since SO and NH groups are related to PVS and PEI, respectively, the spectra confirm the presence of these two polyelectrolytes in the (PEI/PVS) 3 LbL films. The spectrum for the (PEI/PVS) 2 +(PEI/β-Gal) 1 LbL film exhibited the same bands observed for β-Gal and PEI/PVS film, with no band shifts or appearance of additional bands.…”

Ionomers Based on Addition and Ring Opening Metathesis Polymerized 5-phenyl-2-norbornene as a Membrane Material for Ionic Actuators

“…The appearance of the bands at 1130 cm −1 after sulfonation can be attributed to the symmetric vibration of the sulfonic group. In the same time in the spectra of polymers with imidazole and 1-methylimidazole additional bands of symmetric stretching vibration of −SO 3 − group around 1223 cm −1 were revealed [ 45 ]. The absorption band at 1665 cm −1 indicates protonated form of imidazole and 1-metylimidazole [ 46 ].…”

Layer-by-layer films containing emodin or emodin encapsulated in liposomes for transdermal applications

“…3A, where the main bands for emodin in the cast film are also present in the spectrum for the (PEI/PVS) 2 (PEI/EM) 7 LbL film. The Stretching of SO groups of PVS [59] emodin bands at 526, 865, 980, 1060, and 1095 cm −1 are assigned to C H and C C stretching [55][56][57], while the bands at 1030 and 1180 cm −1 for the (PEI/PVS) 10 LbL film are assigned to C C vibration of PEI and stretching of SO groups of PVS polymer [58][59][60]. In the (PEI/PVS) 2 (PEI/EM) 7 spectrum, the major bands originate from emodin.…”