Oxygen Plasma-Mediated Microstructured Hydrocarbon Membrane for Improving Interface Adhesion and Mass Transport in Polymer Electrolyte Fuel Cells

High-Energy Electron Beam-Induced Enhanced Thermoelectric Performance and Irradiation Resistance of PEDOT: PSS

Electron beam (EB) irradiation, a powerful method for electronic and molecular structure regulation of polymer materials, has been proven to be an effective strategy to boost the electrical conductivity (σ) of PEDOT: PSS. However, the irradiation damage from chain scission and cross-linking has an adverse effect on the mechanical and thermal performance. Herein, we propose a convenient approach to enhance irradiation resistance property by adding a chemical oxidant, ammonium persulfate (APS), into PEDOT: PSS, in which irradiation-induced fragmentations can be reaggregated via initiating free radical polymerization through APS. The PEDOT: PSS films doped with 5 wt % APS were exposed to 10 MeV EB irradiation at doses ranging from 2.5 to 20 kGy. The electrical conductivity of PEDOT: PSS-APS films reached 596 S cm-1 at a dose of 2.5 kGy, 2 orders of magnitude higher than that of pure PEDOT: PSS films (4.94 S cm-1), while the Seebeck coefficient remained nearly constant. An optimal thermoelectric power factor (PF) of 16.75 μW m-1 K-2 was achieved. The 1000-fold increase in carrier concentration (n) can elucidate the enhancement in the PF despite the deterioration of carrier mobility. During irradiation, more effective cross-linking occurred in PEDOT: PSS-APS films than in pure PEDOT: PSS. Structural characterization and DFT computational results implied that the imine or protonated amine brought by APS could not only improve the molecular structure but also narrow the band gap, which helped charge transport. The chain fragments caused by chain scission during irradiation could be polymerized via APS into new molecular chains, which influenced the transportation of charge carriers and resulted in enhanced thermal stability and mechanical properties of PEDOT: PSS-APS films. This work provides a simple and innovative treatment to improve both the thermoelectric property and the irradiation resistance of conducting polymers.

Hydrocarbon Ionomeric Binders for Fuel Cells and Electrolyzers

Ionomeric binders in catalyst layers, abbreviated as ionomers, play an essential role in the performance of polymer-electrolyte membrane fuel cells and electrolyzers. Due to environmental issues associated with perfluoroalkyl substances, alternative hydrocarbon ionomers have drawn substantial attention over the past few years. This review surveys literature to discuss ionomer requirements for the electrodes of fuel cells and electrolyzers, highlighting design principles of hydrocarbon ionomers to guide the development of advanced hydrocarbon ionomers.

In Situ Construction of the Fe-Cu Hydroxide Interlocking Structure with Solution-Derived Cu/Ag Current Collectors for Flexible Symmetric Supercapacitors

The current collector serves as a crucial element in supercapacitors, acting as a medium between the electrode material and the substrate. Due to its excellent conductivity, a metal collector is typically favored. Enhancing the binding strength between the collector and the substrate as well as between the collector and the electrode material has emerged as a critical factor for enhancing the capacitance performance. In this study, a Ag film with a grass root-like structure was initially grown on a PI substrate through the surface modification and ion exchange (SMIE) process. This Ag interlocking structure contributes to strong binding between the PI substrate and Ag without compromising the mechanical properties of the Ag film. To further enhance the electrochemical properties at low scan rates, electroless-plated Cu was subsequently deposited on the Ag film to form the Cu/Ag current collector. Moreover, the Cu within the Cu/Ag current collector served as a precursor for the growth of FeOOH-Cu(OH)2 via a two-step in situ method. The resulting FeOOH-Cu(OH)2/Cu/Ag structure as a whole is binder-free. Supercapacitors employing symmetric FeOOH-Cu(OH)2/Cu/Ag structures were assembled, and their energy storage properties were investigated. The solution-based low-temperature process used in this study offers the potential for cost-effective and large-scale applications.

Double-Layer ePTFE-Reinforced Membrane Electrode Assemblies Prepared by a Reverse Membrane Deposition Process for High-Performance and Durable Proton Exchange Membrane Fuel Cells

To promote further commercialization of proton exchange membrane (PEM) fuel cells, developing a novel preparation method for high-performance and durable membrane electrode assemblies (MEAs) is imperative. In this study, we adopt the reverse membrane deposition process and expanded polytetrafluoroethylene (ePTFE) reinforcing technology to optimize the interface combination and durability of MEAs simultaneously for the preparation of novel MEAs with double-layer ePTFE reinforcement skeletons (DR-MEA). With the wet-contact between the liquid ionomer solution and porous catalyst layers (CLs), a tight 3D PEM/CL interface is formed in the DR-MEA. Based on this enhanced PEM/CL interface combination, the DR-MEA exhibits a significantly increased electrochemical surface area, reduced interfacial resistance, and improved power performance compared with a conventional MEA (C-MEA) based on a catalyst-coated membrane method. Furthermore, with the reinforcement of double-layer ePTFE skeletons and the support of rigid electrodes for the membranes, the DR-MEA demonstrates less mechanical degradation than the C-MEA after wet/dry cycle test, reflected in lower increase in hydrogen crossover current, interfacial resistance, and charge-transfer resistance and reduced power performance attenuation. With less mechanical degradation, the DR-MEA therefore shows less chemical degradation than the C-MEA after an open-circuit voltage durability test.