CVD-Deposited Oxygen-Selective Fluorinated Siloxane Copolymers as Gas Diffusion Layers

Abstract

Copolymer thin films of 2,4,6,8-tetramethyl-2,4,6,8tetravinylcyclotetrasiloxane (V4D4), 2-(perfluorohexylethylacrylate) (PFHEA), and 2-(perfluoroalkylethylmethacrylate) (PFEMA) were synthesized via initiated chemical vapor deposition (iCVD) as potential candidates for gas diffusion layers (GDLs) in gas diffusion electrodes (GDEs) for aqueous metal−air batteries. Thin-film GDLs exhibited an average water vapor transmission rate of 7.5 g m −2 day −1 and enhanced oxygen diffusion with oxygen permeabilities as high as 3.53 × 10 −15 mol m m −2 s −1 Pa −1 (10.5 Barrer). The electrochemical performance of GDEs fabricated using commercial catalysts, current collectors, and synthesized GDLs was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and potentiodynamic polarization measurements. The fabricated GDEs exhibited higher oxygen reduction current densities (228.2 mA cm −2 ) compared to commercial GDEs (132.7 mA cm −2 ). Copolymer GLDs exhibited an order of magnitude higher oxygen diffusion (39.5 × 10 −8 cm 2 s −1 ) in GDEs compared to commercial counterparts (1.84 × 10 −8 cm 2 s −1 ). Due to the high oxygen solubility of V4D4 and excellent hydrophobic behavior of PFHEA and PFEMA, their copolymers can effectively promote the diffusion of oxygen and restrict moisture intake, making them ideal materials for GDLs. Combining wellbalanced properties of siloxane and fluorinated polymer chemistries, the iCVD process is an excellent low-cost method for the fabrication of GDLs for metal−air battery applications.

Designing Organic and Hybrid Surfaces and Devices with Initiated Chemical Vapor Deposition (iCVD)

“…Gas diffusion layers (GDLs) in metal–air batteries synthesized by iCVD displayed higher oxygen permeability, higher diffusion, and reduced current densities compared to commercial GDLs. [ 103 ] Metal‐air batteries have garnered significant interest due to their high energy density and low weight. However, critical challenges remain related to the reversibility and lifetime of the GDLs, in which a gaseous reactant comes in contact with a liquid reaction medium.…”

Roll-to-Roll Vapor Deposition of Hydrophobic and Transparent Nano-Adhesive Polymeric Thin Films on Rigid and Flexible Substrates

“…Such a lengthy process has many disadvantages such as the use of aggressive solvents, long production times, requirement for extensive purification, and so forth. In recent decades, “all-dry” surface coating techniques emerged as alternative ways to produce the thin-film coatings of functional polymers in a solventless and one-step manner. − Coatings of various polymers possessing specific functionalities such as superhydrophobicity, superhydrophilicity, antimicrobial, antifogging, and so forth have been deposited on various substrates by vapor-based approaches. Among the different types of vapor deposition technologies, initiated chemical vapor deposition (iCVD) emerged as an efficient way of depositing functional polymers, considering the high deposition rates, conformality, large-area uniformity, and high functional group retention, which are all the desired parameters for an industrially applicable coating process. − In recent literature, there are examples of acrylic PSAs or PSA-related films deposited through iCVD.…”

ACS Editors’ Choice Virtual Collection from I&EC Research

“…We are delighted to collect together [] the 23 articles published in I&EC Research in 2021–2023 (to date) that received designation as ACS Editors’ Choice from ACS Publications. The articles included in this Virtual Collection deal with advances in catalysis (for dry reforming of methane, conversion of glucose to polyols, emission control, and solvent effects on hydroaminomethylation), energy storage, , and chemical recycling of plastics . There are several notable contributions within the realm of thermodynamics that examined CO 2 solubility in polymers, thermodynamics tools used in industry, and equilibria for ternary mixtures of formaldehyde, water, and methanol .…”