Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Proton Conducting”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Proton switching molecular magnetoelectricity

Abstract The convergence of proton conduction and multiferroics is generating a compelling opportunity to achieve strong magnetoelectric coupling and magneto-ionics, offering a versatile platform to realize molecular magnetoelectrics. Here we describe machine learning coupled with additive manufacturing to accelerate the design strategy for hydrogen-bonded multiferroic macromolecules accompanied by strong proton dependence of magnetic properties. The proton switching magnetoelectricity occurs in three-dimensional molecular heterogeneous solids. It consists of a molecular magnet network as proton reservoir to modulate ferroelectric polarization, while molecular ferroelectrics charging proton transfer to reversibly manipulate magnetism. The magnetoelectric coupling induces a reversible 29% magnetization control at ferroelectric phase transition with a broad thermal hysteresis width of 160 K (192 K to 352 K), while a room-temperature reversible magnetic modulation is realized at a low electric field stimulus of 1 kV cm −1 . The findings of electrostatic proton transfer provide a pathway of proton mediated magnetization control in hierarchical molecular multiferroics.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Unraveling the Mechanism of Water-Mediated Sulfur Tolerance via Operando Surface-Enhanced Raman Spectroscopy

While several proton-conducting anode materials have shown excellent tolerance to sulfur poisoning, the mechanism is still unclear due largely to the inability to probe miniscule amounts of sulfur-containing species using conventional surface characterization techniques. Here we present our findings in unraveling the mechanism of water-mediated sulfur tolerance of a proton conductor under operating conditions empowered by surface-sensitive, operando surface-enhanced Raman spectroscopy (SERS) coupled with impedance spectroscopy. Contrary to the conventional view that surface-adsorbed sulfur is removed mainly by oxygen anions, it is found that –SO 4 groups on the surface of the proton conductor are converted to SO 2 by a water-mediated process, as confirmed by operando SERS analysis and density functional theory (DFT)-based calculations. Furthermore, the combination of operando SERS performed on a model electrode and theoretical computation offers an effective approach to investigate into complex mechanisms of electrode processes in various electrochemical systems, providing information vital to achieve the rational design of better electrode materials.

25 ENERGY STORAGE↗
DOE OSTI2026

Benchtop Autonomous Electrochemical Characterization System for Combinatorial Thin-Film Solid Oxide Electrodes

The design of materials for electrochemical energy conversion is complicated by a vast search space of candidate materials and multifaceted property requirements: multicarrier conductivity, stability, and catalytic activity are all necessary but rarely intersect. Although self-driving laboratories are rapidly rising to address such material optimization problems, the required infrastructure for integrated, large-scale robotic facilities can be cost-prohibitive. Here we develop and evaluate a closed-loop measurement system for efficient screening of proton-conducting oxide electrodes for ceramic fuel cells and electrolyzers, building on top of an existing benchtop instrument and integrating techniques for rapid impedance measurement and automated analysis. This system exemplifies a “minimum viable” self-driving implementation that can deliver substantial benefits with relatively simple infrastructure. Combinatorial thin-film microelectrode libraries are characterized with a recently developed joint time-domain and frequency-domain impedance measurement technique, which provides an order-of-magnitude acceleration relative to conventional impedance spectroscopy. The distribution of relaxation times is extracted from impedance data and analyzed without human intervention. These results feed an active learning and Bayesian optimization process that learns to predict electrochemical impedance as a function of material composition, measurement temperature, oxygen partial pressure, and electrical bias, which further reduces the screening time by tenfold with optimized experimental sequences. We apply this system to Ba⁡(Co,Fe,Zr,Y)⁢O 3−𝛿 combinatorial libraries and evaluate its effectiveness for learning material property trends and optimizing expensive-to-evaluate properties such as activation energy. This offers insights into key methodological aspects of practical autonomous experimentation, including surrogate model validation, cost-aware acquisition functions, and high-throughput data interpretation. Our results demonstrate the efficacy of the system for rapidly gathering information, but also highlight real-world experimental challenges of thin-film degradation and numerical instability in surrogate models.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Revealing Phase Heterogeneity in Vertically Aligned Nanocomposites via Plan-View Electron Energy Loss Spectroscopy

Hydrogen utilization in clean energy technologies is challenged by limited storage and transport within materials, owing to the complex hydrogen kinetics at interfaces [1]. Understanding these interfacial mechanisms at the nanoscale is crucial for developing improved materials for hydrogen applications, particularly proton-conducting fuel cells (PCFCs). Vertically aligned nanocomposites (VANs) grown by pulsed laser deposition (PLD) offer a unique platform for investigating the interfacial effects on hydrogen transport due to their well-defined interfaces parallel to the direction of charge transport [2-4]. To investigate hydrogen transport, the two phases within the VANs were chosen as BaZr 0.9 Y 0.1 O 3-x (BZY), a known proton conductor, and Pr 0.1 Ce 0.9 O 2-x (PCO), a mixed ionic-electronic conductor [5]. This PCO-BZY VANs architecture allows the investigation of how the interface between a proton conductor and a mixed conductor influences hydrogen transport. However, because of the small size of hydrogen, it is difficult to discern the nature of its interactions with interfaces from bulk measurements at the macroscale, thus necessitating nanoscale measurements [6]. Electron energy loss spectroscopy (EELS) allows for nanometer-resolution probing of the local atomic structure and chemistry at the BZY/PCO interface. In this study, plan-view analysis of PCO-BZY VANs films was employed to characterize the structure and phase distribution of the VANs and investigate the interface between the nanostructures. The films were imaged using scanning electron microscopy (SEM) in the Hitachi S-4800 SEM, collecting secondary electron images using mixed upper and lower detectors. Then, plan-view transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) EELS were employed using a JEOL ARM300 microscope operated at 300kV with a Gatan K3 GIF Continuum detector to study the distribution of the BZY and PCO phases through the film. As a result, spectrum images were acquired at a dispersion of 0.18eV per channel and denoised afterward by principal component analysis (PCA) method.

Griffin, Elizabeth [Northwestern University, Evans↗
NASA NTRS2003

Rod/Coil Block Copolyimides for Ion-Conducting Membranes

Rod/coil block copolyimides that exhibit high levels of ionic conduction can be made into diverse products, including dimensionally stable solid electrolyte membranes that function well over wide temperature ranges in fuel cells and in lithium-ion electrochemical cells. These rod/coil block copolyimides were invented to overcome the limitations of polymers now used to make such membranes. They could also be useful in other electrochemical and perhaps some optical applications, as described below. The membranes of amorphous polyethylene oxide (PEO) now used in lithium-ion cells have acceptably large ionic conductivities only at temperatures above 60 C, precluding use in what would otherwise be many potential applications at lower temperatures. PEO is difficult to process, and, except at the highest molecular weights it is not very dimensionally stable. It would be desirable to operate fuel cells at temperatures above 80 C to take advantage of better kinetics of redox reactions and to reduce contamination of catalysts. Unfortunately, proton-conduction performance of a typical perfluorosulfonic polymer membrane now used as a solid electrolyte in a fuel cell decreases with increasing temperature above 80 C because of loss of water from within the membrane. The loss of water has been attributed to the hydrophobic nature of the polymer backbone. In addition, perfluorosulfonic polymers are expensive and are not sufficiently stable for long-term use. Rod/coil block copolyimides are so named because each molecule of such a polymer comprises short polyimide rod segments alternating with flexible polyether coil segments (see figure). The rods and coils can be linear, branched, or mixtures of linear and branched. A unique feature of these polymers is that the rods and coils are highly incompatible, giving rise to a phase separation with a high degree of ordering that creates nanoscale channels in which ions can travel freely. The conduction of ions can occur in the coil phase, the rod phase, or both phases.

Meador, Mary Ann B.↗
DOE OSTI2025

Synthesis of highly sulfonated 2,6-diphenyl-p-Phenylene oxide: A highly conductive membrane

Highly sulfonated aromatic polymers are desired for the possible highest performance of polymer electrolytes in fuel cells and electrolyzer applications. Here, we reported the method to prepare highly sulfonated 2,6-diphenyl-p-phenylene oxide (SP3O), a commercially available aromatic polymer, with the highest IEC of 4.42 meq/g. Three sulfonation reagents including chlorosulfonic acid (HSO3Cl), concentrated sulfuric acid (conc. H2SO4), and trimethylsilyl chlorosulfonate (TMSCS) were investigated for single and two-step sulfonation reactions. In addition, DMSO-assisted thermal crosslinking method was applied to prepare crosslinked SP3O membranes to improve their mechanical strength and film-forming ability. Proton exchange membrane from crosslinked SP3O displayed a proton conductivity as high as 250 mS/cm at 95 % RH and 60 °C.

Khomein, Piyachai↗
DOE OSTI2023

Unraveling the core of fuel cell performance: engineering the ionomer/catalyst interface

The biggest obstacle to the widespread implementation of polymer electrolyte membrane fuel cells (PEMFCs) is their cost, primarily due to the use of platinum catalysts. The high intrinsic catalyst activity exhibited on a rotating disk electrode (RDE) is rarely realized in a membrane electrode assembly (MEA), which is a long-standing challenge for PEMFCs and a cause of low catalyst utilization. To translate the high RDE performance of a catalyst into a MEA, the design of an ideal ionomer/catalyst interface is proposed: a thin, conformal ionomer film covers the maximum surface of a Pt nanoparticle and thus simultaneously maximizes catalyst utilization, (i.e., high mass activity and electrochemically active surface area) and O 2 diffusion rate (i.e., high current density performance) without compromising proton conduction. Building such an interface is a long-standing challenge due to the lack of interaction between the ionomer and catalyst particles, resulting in large ionomer agglomerates and inhomogeneous ionomer coverage over the catalyst nanoparticle, with consequent poor fuel cell performance. In this work, this ionomer/catalyst interface has been engineered, utilizing the electrostatic attraction between positively charged catalyst and negatively charged ionomer particles in a catalyst ink and preserved in a solid catalyst layer. As a result, this interface leads to previously unachieved proton exchange membrane fuel cell performance in terms of both catalyst utilization (75% vs. 45%) and peak/rated power density (i.e., 1.430/0.930 W cm -2 , H 2 /air, cathode Pt loading: 0.1 mgPt cm -2 ) for pure Pt catalysts, even better than those of Pt alloy catalysts. This work demonstrates the formation of an interface in the liquid phase (using ultra-small-angle X-ray scattering in combination with cryo-TEM, isothermal–titration–calorimetry) and the preservation of the interface in the solid catalyst layer (using TEM) and estimates the effective coverage and thickness of the ionomer film (using limiting current density, RDE and fuel cell performance).

25 ENERGY STORAGE↗
DOE OSTI2022

Revitalizing interface in protonic ceramic cells by acid etch

Protonic ceramic electrochemical cells hold the promise to be operated at intermediate temperatures below 600 °C. Although the high proton conductivity of the bulk electrolyte has been demonstrated, it cannot be fully utilized in electrochemical full cells due to unknown causes. A practical solution is thus urgently needed. Here we showed that it comes from poor contacts between the low-temperature processed oxygen electrode-electrolyte interface. We demonstrated that a simple acid treatment can effectively rejuvenate the high-temperature annealed electrolyte surface, resulting in reactive bonding between the oxygen electrode and the electrolyte and improved electrochemical performance and stability. This enables exceptional protonic ceramic fuel-cell performance down to 350 °C, with peak power densities of 1.6 W cm -2 at 600 °C, 650 mW cm -2 at 450 °C, and 300 mW cm -2 at 350 °C, as well as stable electrolysis operations at large current densities above 3.9 A cm -2 under 1.4 V applied voltage at 600 °C. Furthermore, our work highlights the critical role of interfacial engineering in ceramic electrochemical devices and offers new understanding and practices towards sustainable energy infrastructure.

08 HYDROGEN↗
DOE OSTI2020

Elucidating the Role of Ionomer in the Performance of Platinum Group Metal-free Catalyst Layer via in situ Electrochemical Diagnostics

The ionomer content in platinum group metal (PGM)-free polymer electrolyte fuel cell (PEFC) cathode catalyst layer (CCL) plays an important role in the electrode gas transport properties, proton conductivity, and hence, membrane electrode assembly (MEA) performance. In this work, the ionomer content in the CCL is varied, influencing electrode microstructure by altering porosity, tortuosity, as well as ionomer distribution and coverage of the catalyst particles. A novel technique consisting of a H 2 pump, combined with a Pt black sensor layer, is used to measure the bulk mass transport resistance of a series of PGM-free CCL prepared with different ionomer contents. The values for bulk electrode mass transport resistance are contrasted with electrode proton transport resistance in the cathode catalyst layer, establishing a clearly defined trade-off between two key performance limiting phenomena and identifying a need for novel PGM-free electrode fabrication strategies.

25 ENERGY STORAGE↗
NASA NTRS2003

Novel Ordered Crown Ether-Containing Polyimides for Ion Conduction

We report the synthesis and characterization of thermally-stable polyimides for use as battery and fuel cell electrolyte membranes. Dianhydrides used were 1,4,5,8- naphthalenetetracarboxylic dianhydride and/or 4,4'-(hexafluoroisopropylidene)diphthalic anhydride. Diamines used were anti-4,4-diaminodibenzo-l8-crown-6, 4,4'- diaminodibenzo-24-crown-8, 2,2-bis(4-aminophenyl)hexafluoropropane, and/or 2,5- diaminobenzenesulfonic acid. The polymers were characterized using electrochemical impedance spectroscopy (EIS), thermal analysis and X-ray diffraction. Polymers containing the hexafluoroisopropylidene (HFIP) group were soluble in common organic solvents, while polymers without the HFIP group were very poorly soluble. Sulfonation yields polymers that are sparingly soluble in aqueous base and/or methanol. Degree of sulfonation, determined by titration, was between one and three sulfonate groups per repeat unit. Proton conductivity was determined as a function of water content, with a maximum conductivity of l x 10(exp -2) per centimeter when fully hydrated. Crown ether-containing polymers exhibit a high degree of order that may be indicative of crown ether channel formation, which may facilitate Li(+) transport for use in battery membranes.

Irvin, Jennifer A.↗
DOE OSTI2026

How Proton Incorporation Reshapes Lattice Dynamics In BaSnO 3 ‐Type Proton Conductors

Proton conduction in acceptor-doped perovskites is fundamentally a vibronic process: mobile H + and D + do not move independently, but dynamically co-vibrate with the surrounding oxygen–metal framework. Direct experimental evidence for this behavior is presented using in situ 119⁢ 𝑆⁢𝑛 nuclear resonance vibrational spectroscopy (NRVS) on hydrated, deuterated, and dry 𝐵⁢𝑎⁢𝑆⁢𝑛 1−𝑥⁢ 𝑌 𝑥 ⁢𝑂 3−𝛿 . Hydration induces systematic redistributions in the Sn-projected phonon density of states (PDOS), including an upshift of the first spectral moment by about 0.4 meV, indicating a stiffening of the extended Sn–O network. H/D isotopic substitution leaves the Sn-projected PDOS largely unchanged, with only subtle isotope-dependent spectral reweighting, demonstrating that protonic degrees of freedom are not localized oscillators but are embedded in collective lattice modes. These results are rationalized using a classical coupled proton–phonon oscillator model that links the observed PDOS variations to changes in effective force constants and vibrational mass terms. The model captures how H + and D + participate in cooperative lattice dynamics rather than forming isolated OH/OD entities. Overall, NRVS probes proton–lattice coupling in ceramic proton conductors and quantitatively describes how protonic defects modulate host lattice dynamics to enable phonon-assisted long-range proton transport.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Cryo-EM structures of Escherichia coli cytochrome bo 3 reveal bound phospholipids and ubiquinone-8 in a dynamic substrate binding site

Two independent structures of the proton-pumping, respiratory cytochrome bo3 ubiquinol oxidase (cyt bo 3 ) have been determined by cryogenic electron microscopy (cryo-EM) in styrene–maleic acid (SMA) copolymer nanodiscs and in membrane scaffold protein (MSP) nanodiscs to 2.55- and 2.19-Å resolution, respectively. The structures include the metal redox centers (heme b, heme o 3 , and Cu B ), the redox-active cross-linked histidine–tyrosine cofactor, and the internal water molecules in the proton-conducting D channel. Each structure also contains one equivalent of ubiquinone-8 (UQ8) in the substrate binding site as well as several phospholipid molecules. The isoprene side chain of UQ8 is clamped within a hydrophobic groove in subunit I by transmembrane helix TM0, which is only present in quinol oxidases and not in the closely related cytochrome c oxidases. Both structures show carbonyl O1 of the UQ8 headgroup hydrogen bonded to D75I and R71 I . In both structures, residue H98 I occupies two conformations. In conformation 1, H98 I forms a hydrogen bond with carbonyl O4 of the UQ8 headgroup, but in conformation 2, the imidazole side chain of H98 I has flipped to form a hydrogen bond with E14 I at the N-terminal end of TM0. We propose that H98 I dynamics facilitate proton transfer from ubiquinol to the periplasmic aqueous phase during oxidation of the substrate. Computational studies show that TM0 creates a channel, allowing access of water to the ubiquinol headgroup and to H98 I .

bioenergetics↗
DOE OSTI2020

Hydrous Nickel–Iron Turnbull’s Blue as a High-Rate and Low-Temperature Proton Electrode

Proton batteries are emerging as a promising solution for energy storage; however, their development has been hindered by the lack of suitable cathode materials. Herein, a hydrous Turnbull’s blue analogue (TBA) of Ni[Fe(CN) 6 ] 2/3 ·4H 2 O has been investigated as a viable proton cathode. Particularly, it shows an extremely high rate performance up to 6000 C (390 A g –1 ) at room temperature and delivers good capacity values at a low temperature of -40 °C in an aqueous electrolyte. The excellent rate capability is also amenable to high mass loadings of 10 mg cm –2 . Such fast and low-temperature rate behavior likely stems from the fast proton conduction that is afforded by the Grotthuss mechanism inside the TBA structure. Furthermore, advanced characterization, including in operando synchrotron X-ray diffraction (XRD), and X-ray absorption near-edge structure (XANES) were employed to understand the changes of crystal structures and the oxidation-states of metal elements of the electrodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Design of non-fluorinated proton exchange membranes from Poly(Terphenyl fluorenyl isatin) with fluorene-linked sulfonate groups and microblock structures

Proton exchange membranes (PEMs) are essential components in energy storage and conversion devices, such as fuel cells and electrolyzers. Here, in this study, we developed a series of non-fluorinated PEMs from poly(terphenyl fluorenyl isatin) with fluorene-pendent disulfonate groups. These polymers feature a microblock structure composed of hydrophobic blocks, hydrophilic blocks, and alternating blocks, arising from the differences in reactivity, concentration, and solubility between the hydrophobic p-terphenyl and hydrophilic disulfonated fluorene monomers. As a result, the sulfonic acid groups are unevenly distributed along the polymer chains, forming densely charged regions (IEC = 3.52 meq/g) with large ion clusters and lightly charged regions (IEC = 2.16 meq/g) with small ion clusters. This microstructure, combined with the degree of sulfonation, significantly influences the overall properties of the membranes, including robust mechanical strength (47.1–63.2 MPa), high thermal stability (up to 270 °C), low swelling ratio (18–25% at 80 °C), and high proton conductivity (136–169 mS/cm in deionized water at 80 °C). The PFLSH60 membrane demonstrated comparable fuel cell performance to Nafion 212. Its hydrogen crossover current density was more than two times lower (0.86 mA/cm 2 for PFLSH60 compared to 1.83 mA/cm 2 for Nafion 212) under testing conditions of 80 °C and 100% RH. This significantly reduced crossover improves fuel utilization in fuel cell stacks. This work offers valuable insights into the design of robust, high-performance PEMs by systematically analyzing the relationships between membrane structure, properties, and performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Experimental Studies of Graphene-Coated Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

The two main technical limitations of direct methanol fuel cells (DMFCs) are the slow kinetic reactions of the methanol oxidation reaction (MOR) in the anode and the crossing over of unreacted methanol through the proton exchange membrane (PEM). It is a common practice to use Nafion membranes as PEMs, which have high ion exchange capacity. However, Nafion-based membranes also have high fuel permeability, decreasing fuel utilization, and reducing the potential power density. This article focuses on using graphene-coated (Gr-coated) PEMs to reduce fuel crossover. Protons can permeate across graphene, and thus, it can be employed in various devices as a proton conductive membrane. Here, we report the efficiency of Gr-coated Nafions. We tested performance and crossover at three different temperatures with four different fuel concentrations and compared it to a Nafion PEM that underwent the same test conditions. We found that the adhesion of Gr on to PEMs is insufficient for prolonging fuel cell operation, resulting in Gr delamination at high temperatures and higher fuel crossover values compared to lower temperature testing. Furthermore, the results for 7.5M methanol fuel show a reduction of up to 25% in methanol crossover, translating to a peak power density that increases from 3.9 to 9.5 mW/cm 2 when using a Gr-coated PEM compared to a Nafion PEM at 30 °C.

25 ENERGY STORAGE↗
DOE OSTI2020

Novel Ionomers and electrode structures for improved PEMFC electrode performance at low PGM loadings (Final Report)

In this project, the objective is to develop new ORR electrocatalysts on optimized supports which can exceed all of the Department of Energy (DOE) 2020 targets listed in DE-FOA-0001412 directly relevant to the subtopic. This project’s approach is to develop novel, electrode-specific ionomers, and integrate them with state-of-the-art NSTF electrocatalyst powder to develop a cathode electrode achieving >= 044 A/mg PGM mass activity, <=30% mass activity loss during metal cycling, and <=0.125 g PGM /kW performance under DOE testing protocols. Ionomer O 2 permeability and proton conductivity will be increased by up to 1.5X over the baseline 3M800 perfluorosulfonate (PFSA) ionomer to enhance cathode electrode performance. Integration of cathode NSTF powder into an ionomer-containing electrode will increase the surface enhancement factor (SEF) to >=40 cm 2 PGM /cm 2 GEO allowing NSTF containing cathodes to exceed DOE MEA robustness targets. This report summarizes this project’s progress towards meeting the stated objectives and includes a summary of significant findings, conclusions, and developments over the entire project period from Oct. 1 st 2016 – Jan. 31 st 2020. This work has overcome key operation robustness issues with classic NSTF electrodes, identified pathways to improved dispersed and dispersed NSTF cathode performance, developed novel ionomers with high bulk conductivity and oxygen permeability, demonstrated exceptional support-independent electrode activity, and significantly increased metal and support stability through ionomer development. At this point, Tufts, MTU and all 5 FCPAD national labs have been involved, and contributed to, the improvements, learning and achievements of this work. Over the course of this project, more than 50 grams of dispersed NSTF powder in 15 different configurations have been generated, paving the way for scaleup within 3M. These whiskers have been processed in multiple ways, including acid leaching, powder-annealed, and sonicated by various means. For Task 2, 27 different types of ionomers were tested, 19 of which were made for the first time during the course of this project. 377 electrode inks with both NSTF and metal-on-carbon catalysts with I/C ratios from 0.2 to 1.2 were generated and mostly coated on a 3M pilot manufacturing line resulting in more than 700 different electrode types.

08 HYDROGEN↗
DOE OSTI2026

Quantification of [MTBD][beti] loading and its effects on Pt/HSC electrode performance in hydrogen fuel cells

High surface area carbon-supported platinum catalysts (Pt/HSC) are widely used in polymer electrolyte membrane fuel cells but often suffer from limited proton and oxygen transport within porous domains. To address these challenges, we integrate the ionic liquid [MTBD][beti] into Pt/HSC catalyst layers using two deposition methods-one-pot and sequential deposition-to tune IL distribution within micropores and mesopores. A combination of ex situ and in operando techniques were employed to elucidate electrode structure-performance relationships across a range of IL loadings. Sequential deposition achieved more efficient pore filling and higher IL retention at lower IL:C ratios, enabling enhanced proton conductivity and protection of active sites. Compared to the IL-free Pt/HSC, IL-modified electrodes demonstrated up to 28% improvement in mass activity and enhanced high-current-density performance under low relative humidity, while maintaining comparable performance under humidified conditions. Electrochemical impedance spectroscopy and CO displacement experiments reveal that improvements are linked to reduced ionic resistance and lower sulfonate adsorption on Pt sites, rather than changes in electrochemical surface area. However, excessive IL loading leads to mass transport losses. These results highlight the importance of selective pore filling and efficient IL distribution in achieving kinetic gains without compromising ionic and gas transport.

08 HYDROGEN↗