Understanding the Behavior of Electrosprayed Carbon Black‐Nafion Composite Layers

Abstract

Electrosprayed composite films prepared from carbon and Nafion are especially suitable to be applied as microporous layers and protective coatings for a number of for proton exchange membrane fuel cell (PEMFC) components, due to of their particular properties. The electrospray deposition of carbon inks is a complex process that requires further study. In order to gain insight into the factors influencing the characteristics of electrosprayed films, the effect of some parameters has been analyzed. The solvent nature, the Nafion to carbon ratio in the ink, the ionization voltage (positive or negative) and the polymer distribution on the carbon surface are some of the studied variables. Surface characterization of these layers by techniques, such as XPS, SEM or thermal decomposition has provided very useful information about the structure of the layers and the interaction between their components. The results show that electrospray ionization induces a strong adsorption of the sulfonic groups of the ionomer on the carbon black surface, which is probably responsible for the high stability and durability of the layers and their superhydrophobic character. To our knowledge, this is the first study devoted to the analysis of the particular carbon‐Nafion interactions in electrosprayed films.

Electrochemical Behavior of Different Diffusional Redox Probes on a Porous Acetylene Black Electrode: Mass Transport Modes and Electrostatic Effects

“…For instance, Nafion is used to block out the anionic (negatively charged) ascorbate and accumulate the cationic (positively charged) dopamine in sensing electrodes. − In the same system, the accumulation (trapping) effect of the Nafion and the subsequent signal enhancement have also been demonstrated. Furthermore, in the AB and Nafion IPA solution, aggregates between AB and Nafion are formed with sulfonic groups heading toward AB, as stated by Conde and Chaparro . This would finally result in AB aggregates covered by negatively charged hydrophobic chains.…”

“…Thus, the C 1s peak was deconvoluted into nine peaks corresponding to the functional groups C�C (sp 2 , 284.42 eV), C−C (sp 3 , 284.80), C−OH (sp 3 , 286.25 eV), C�O (sp 2 , 288.28 eV), and π−π*transition (290.7 eV), plus the binding energies corresponding to C−F bonds, namely, -OCF 2 (289.50 eV), −CF 2 (291.95 eV), and −CF 3 (293.62 eV), in good agreement with previously reported binding energies. 27 In Figure S4, the O 1s peak was deconvoluted into three peaks corresponding to the functional groups C�O and C−O (532.87 eV) and oxygen in the −SO 3 − group, which is bound to sulfur within the sulfonic acid of the side chain yielding O 1s signal at 532.25 eV. Furthermore, the oxygen in the ether configuration (−F 2 C−O−CF 2 −) is found at 535.45 eV.…”

“…Furthermore, in the AB and Nafion IPA solution, aggregates between AB and Nafion are formed with sulfonic groups heading toward AB, as stated by Conde and Chaparro. 27 This would finally result in AB aggregates covered by negatively charged hydrophobic chains. This conclusion has also been reported in ref 52 relative to CB plus Nafion inks, where it is indicated that the interactions between CB particles and Nafion are due to the appearance of van der Waals forces between the Nafion-covered nanoparticles that would cause aggregration.…”

Electrospray Deposition: A Breakthrough Technique for Proton Exchange Membrane Fuel Cell Catalyst Layer Fabrication

“…The study revealed a strong and stable interaction between the sulfonic groups of the Nafion and the carbon black surface, which is probably the result of the fast desolvation of the adsorbed ionomer during the ionization process. This interaction is believed to favor a better coverage of the carbon surface with the polymer chains and leads to a particular arrangement of the Nafion with fluorocarbon backbones oriented toward the outer part of the aggregates …”

“…This interaction is believed to favor a better coverage of the carbon surface with the polymer chains and leads to a particular arrangement of the Nafion with fluorocarbon backbones oriented toward the outer part of the aggregates. 49 Electrosprayed catalyst layer properties were further analyzed ex situ for a more complete insight into their unparalleled properties. Mass-transport properties were studied by the hydrogen limiting-current technique and correlated with their water-vapor uptake capability.…”