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

Abstract

This Spotlight article presents the state-of-the-art of electrospray deposition technique applied to the fabrication of proton exchange membrane fuel cell (PEMFC) components, mainly focusing on catalyst layers in gas diffusion electrodes. The atomization of a suspension of particles over a substrate under the influence of a strong electric field results in the growth of a film with macroporous morphology and many interesting properties. This so-called electrospray deposition has reported many noteworthy beneficial effects for the fabrication of the catalyst layers of gas diffusion electrodes of PEMFCs. The electrosprayed catalyst layers prepared from suspensions of catalyst particles and ionomers present a dendritic macroporous morphology with superhydrophobic character that improves the water management inside the cell and increases the performance by ∼20% with respect to standard electrodes prepared by airbrushing. Other interesting effects observed with electrosprayed catalyst layers are increased catalyst utilization and water absorption capabilities of the ionomer, improved performance under nonhumidified conditions, and a reduction in catalyst degradation. In addition, the electrospray deposition decreases platinum losses during fabrication thanks to the attractive electrostatic forces between the ion mist and the substrate compared with regular ink-based spray methods.

Colloidal Stability of PFSA-Ionomer Dispersions. Part I. Single-Ion Electrostatic Interaction Potential Energies

“…Proton-exchange-membrane fuel cells offer a promising replacement for traditional combustion engines that have deleterious emissions. The catalyst layers of these cells are currently produced via ink fabrication and deposition involving empirically formulated colloidal dispersions of the perfluorinated sulfonic acid polymer (PFSA) and other ionomers. − Colloidal dispersions are commonly assumed to be stable when the total interparticle potential-energy maximum is more than a few k B T units, where k B is Boltzmann’s constant and T is absolute temperature. − When the potential-energy maximum is less than this value or is negative everywhere, the dispersion is unstable and particles aggregate. ,,, Aggregation kinetics in a quiescent dispersion often follows perikinetic Smoluchowski kinetics that depend strongly on the pairwise interaction energies between particles. ,,, For electrostatically stabilized charged particle dispersions in electrolyte-supporting solvents, the pairwise interaction potential traditionally consists of a Hamaker attractive interaction and a repulsive electrostatic interaction (i.e., so-called DLVO theory). − The electrostatic pair potential originates from the overlap of diffuse double layers encompassing two charged interacting particles. When the opposing particles separate significantly beyond the Debye length, the intervening solution is electrically neutral.…”

Electrospray Deposition of PEDOT:PSS on Carbon Yarn Electrodes for Solid-State Flexible Supercapacitors

“…In the process of being transported to the substrate, the solution forms a spray plume. The solvent fully (or partially) evaporates, and the droplet size decreases until reaching the Rayleigh limit, creating a thin film of PEDOT:PSS on the substrate . During ESD deposition, two factors are most critical: (i) achieving uniform PEDOT:PSS droplets by exploiting the electrospray mode of deposition and (ii) deposition of hydrophilic PEDOT:PSS thin films on the carbon yarn substrates by controlling the wettability of PEDOT:PSS droplets.…”

“…The solvent fully (or partially) evaporates, and the droplet size decreases until reaching the Rayleigh limit, creating a thin film of PEDOT:PSS on the substrate. 47 During ESD deposition, two factors are most critical: (i) achieving uniform PEDOT:PSS droplets by exploiting the electrospray mode of deposition and (ii) deposition of hydrophilic PEDOT:PSS thin films on the carbon yarn substrates by controlling the wettability of PEDOT:PSS droplets. Various techniques can be employed to reduce the surface tension of the PEDOT:PSS solution such as adding a surfactant to the spray solution or mixing secondary solvents with lower surface tension.…”

Customized Patterning of Deep Nanowell Structures in Polymer Electrolyte Membranes for Highly Enhanced Fuel Cell Performances

“…One of the most effective strategies for reducing Pt use in the cathode is to increase the three-phase boundary by modulating the interface structure between the polymer electrolyte membrane (PEM) and catalyst layer (CL). − It has been also reported that in the CL with a thickness of several micrometers in general, catalysts located far from the membrane surface exhibit low ORR performance . Accordingly, to improve the PEMFCs’ performance and to reduce Pt usage, it is required to place Pt particles in closer proximity to the membrane by roughening the membrane surface.…”