Reduced Transport Resistance Research Articles

Structured mesh material with gradient surface wettability for high-power-density proton exchange membrane fuel cells

ABSTRACT A compact cell structure is highly desirable for next-generation high-power-density proton exchange membrane (PEM) fuel cell (>9.0 kW L−1). A novel integrated bipolar plate (BP) – gas diffusion layer (GDL) structure utilizing porous material is a promising configuration, which not only improves output power due to the reduced transport resistance but also reduces cell thickness. Herein, we propose a structured mesh material with gradient surface wettability for this cell structure, which is characterized by an ordered skeleton in the three-dimensional (3D) space with high structure design flexibility. It is experimentally found that the structured mesh material shows higher performance than serpentine and parallel flow fields. Meanwhile, 3D modeling work on an automobile fuel cell (cell area: 245.76 cm2) with the distribution zones of dot matrix structure for hydrogen, air and coolant flow, is conducted, and it is found that the structured mesh material effectively decreases the concentration and electric ohmic losses in comparison with the traditional “BP/flow field + GDL” structure, improving power density with uniform distribution characteristics. Moreover, the gradient wettability on the mesh surface helps promote the water detach the GDL and hold the residual liquid water in the top region, optimizing the water management.

Electrostatic Potential of Functional Cations as a Predictor of Hydroxide Diffusion Pathways in Nanoconfined Environments of Anion Exchange Membranes.

Nanoconfined anion exchange membranes (AEMs) play a vital role in emerging electrochemical technologies. The ability to control dominant hydroxide diffusion pathways is an important goal in the design of nanoconfined AEMs. Such control can shorten hydroxide transport pathways between electrodes, reduce transport resistance, and enhance device performance. In this work, we propose an electrostatic potential (ESP) approach to explore the effect of the polymer electrolyte cation spacing on hydroxide diffusion pathways from a molecular perspective. By exploring cation ESP energy surfaces and validating outcomes through prior ab initio molecular dynamics simulations of nanoconfined AEMs, we find that we can achieve control over preferred hydroxide diffusion pathways by adjusting the cation spacing. The results presented in this work provide a unique and straightforward approach to predict preferential hydroxide diffusion pathways, enabling efficient design of highly conductive nanoconfined AEM materials for electrochemical technologies.

Reducing transport resistance in highly concentrated fine-grained slurry pipelines by vibration-induced fluidization

Reducing the resistance in slurry pipeline systems is a major concern in dredging projects because of its high energy consumption, which can reach up to 80% of the total energy consumed. In this study, a resistance reduction method (a vibratory resistance reducer) for highly concentrated fine-grained slurry pipeline transport based on vibration-induced fluidization was introduced. Further, the major factors influencing the resistance reduction were quantitatively explored through slurry pipeline transport tests. The experimental results show that the proposed method significantly reduces resistance in the slurry pipeline. The resistance loss reduction rate increases with the vibration frequency and an optimal vibration frequency exists for the resistance reduction. Moreover, vibration-induced fluidization results in a higher resistance reduction for a smaller transport capacity of the pipeline. For silt and fine sand, coarser slurry particles have smaller optimal vibration frequency, and higher resistance reduction rate of slurry pipeline transport under a certain vibration frequency. Finally, using the experimental data, an empirical formula for estimating the resistance loss reduction rate of slurry pipeline transport using a vibratory resistance reducer was proposed.

Hydrophilic TiO2@MXene membrane for direct generation of monodisperse submicron water-in-diesel emulsion and its microexplosion performance

Hydrophilic membrane interfaces, especially that of particle-packed ceramic membranes, are generally not suitable for use as emulsification media for generating monodisperse water-in-oil emulsions. This is because their short adjacent pore distances tend to cause droplet coalescence. In this study, a facile in situ oxidation strategy was proposed to develop ceramic-based hydrophilic TiO2@MXene membranes for directly generating monodisperse submicron water-in-diesel emulsions using membrane emulsification technology at room temperature. Through the in situ oxidation process, numerous TiO2 nanoparticles were grown on the surface of MXene nanosheets to form a novel TiO2@MXene composite structure with a membrane pore size of 12.2 nm. This structure is characterized by abundant transport channels, remarkably robust stability, and high water permeance of 154.8 L m−2 h−1 bar−1. Because of the long horizontal distance between adjacent nanosheets and the substantially reduced transport resistance, water droplets can roll smoothly along the TiO2@MXene nanochannels and then converge with the diesel, thus reducing the risk of emulsion coalescence. The mean droplet size of the emulsions can be controlled from ∼100 to 500 nm by regulating the emulsification conditions. The optimal emulsions exhibited excellent monodispersity with an average droplet size of 157.2 nm and possessed relatively excellent long-term stability (up to 45 days). Moreover, the emulsions showed a positive microexplosion phenomenon during heating. The maximum microexplosion strength of the emulsions reached 6.31 m s−1 (at 20% water content), which provides a reliable theoretical basis for research on emulsified diesel as an alternative to traditional fuels.

Enhanced performance of thin-film nanocomposite membranes achieved by hierarchical zeolites for nanofiltration

Nanosized zeolite molecular sieves are increasingly explored for developing high-performance nanocomposite membranes, mainly because of their ordered pore structures and remarkable thermal stability. In this study, hierarchical nanosized aluminophosphate molecular sieves [AlPO-5 (AFI)] were synthesized as functional fillers to construct thin-film nanocomposite (TFN) membranes. Nanosized AlPO-5 was effectively positioned onto porous polysulfone supports via a filtration-assisted method, followed by in situ interfacial polymerization to construct a polyamide layer atop the modified supports. The synthesized nanosized AlPO-5 crystals have both intrinsic micropores and abundant intracrystalline mesopores. SEM and AFM analyses reveal that the introduction of AlPO-5 not only enhanced the surface roughness of TFN membranes with valley-shaped surface but also substantially decreased the thickness of a polyamide layer compared to nodular-shaped TFC membranes. These differences are mainly ascribed to retarded piperazine diffusion and positioned AlPO-5 nanoaggregates. The role of AlPO-5 loading in overall separation performance of TFN membranes was studied. The best-performing TFN membranes showed the highest water permeability of 23.2 L m−2 h−1 bar−1, nearly twice that of unmodified TFC membranes, while maintaining a high salt rejection of 97.5%. The thickened and roughened polyamide layer with reduced transport resistance as well as intrinsic abundant mesopores of AlPO-5 fillers mainly contribute to the enhanced water transport. This study highlights the usage of hierarchical zeolite molecular sieves to fabricate high-permeable polyamide membranes for elevated nanofiltration performance.

Construction of poly(vinyl alcohol)-based ionogels with continuous ion transport channels enables high performance ionic soft actuators

A superior PVA-based ionic actuator was developed by forming continuous ion transport channels via ion–dipole interaction at the phase interface, while strong adhesion of the electrode/ionogel reduced transport resistance, achieving high actuating properties.

Microstructuring of Electrodes for Li-Ion Batteries By Means of Laser Machining and Microembossing – a Promising Approach to Overcome Transport Limitations and to Improve Their Fast Charging Capability

In addition to costs, safety and durability, energy density and fast-charging capability are the key requirements for Li-ion batteries for automotive applications. To meet these requirements, new cell chemistries are being developed, such as silicon-containing anodes. Likewise, electrode designs with high mass loading, respectively high layer thickness and a high density are being researched. However, such high-energy electrodes exhibit significant transport resistances due to their design, which has a negative effect on the electrode kinetics and thus the fast-charging capability.In our presentation, we will use the example of NMC-based cathodes and graphite anodes to show how the electrode kinetics can be improved by systematically influencing the electrode microstructure and the electrode surface. Short and ultra-short pulsed near infrared laser processes as well as mechanical embossing methods using needle type tools are used. In doing so, near-surface “quasi 2D” modification and three-dimensional structuring of the electrodes active mass were investigated.We will demonstrate how a specific adjustment of the laser parameters e.g. energy per unit length allows a roughening of the electrode surface and a selective removal of the binder-conductive additive compound without damaging or significantly ablating the active material. This “quasi 2D” modification offers the advantage that the capacity is largely retained. Electrochemical analyses such as rate tests show an improvement of up to 25% in the fast-charging capability. Electrochemical impedance analyses using symmetrical cells underline these findings by revealing a reduced transport resistance. In tendency, the higher the laser energy input and surface roughness, the more pronounced the observed effects – with a loss of active material also being observed at high laser input.Comparatively, perforated (i.e. three-dimensionally microstructured) electrodes, are investigated. The results obtained are comparable to the surface-near modification. However, in the case of perforation by laser, about 10% of active material is removed, which is reflected in a corresponding loss of capacitance. Electrodes perforated by microembossing also show significantly improved electrode kinetics, but without material removal and capacity loss. This makes microembossing appear to be an interesting and alternative microstructuring process. Finally, the combination of both processes – “quasi 2D” plus 3D – is investigated to combine the beneficial effects of both.The differently processed electrodes were also subjected to various rapid aging tests such as 100 charge/discharge cycles with a current mode of C/3 as well as interspersed fast charging cycles. The modified graphite anodes exhibit a lower tendency to Li plating than unprocessed reference anodes, and the degradation is lower than for the reference electrodes. For instance, the perforated anodes exhibited a capacity retention of 96%.In addition to a significant improvement of the electrochemical performance, a clear enhancement of the electrolyte wetting is demonstrated. Droplet tests and rising height tests showed an improved wettability by a factor of 4 to 5, depending on the type of microstructuring.The process development and the electrochemical analyses were closely accompanied by microscopic and material analyses e.g. by means of white light interferometry, nano-CT, SEM and TEM as well as Raman spectroscopy to reveal the most important process-microstructure-property relationships.To sum it up, we believe that the presented microstructural modifications are very attractive – both, in terms of electrochemical performance as well as from a manufacturing point of view. Figure 1

Wetting-Induced Water Promoted Flow on Tunable Liquid-Liquid Interface-Based Nanopore Membrane System.

Membrane separation provides effective methods for solving the global water crisis. Contemporary membrane systems depend on interfacial interactions between liquid and solid membrane matrixes. However, it may lead to a limiting permeate flux due to the large flow resistance at hydrophobic liquid-solid interfaces. Herein, the liquid-liquid interface with improved interface energy is reversibly introduced in membrane systems to boost wetting and reduce transport resistance. A series of interfaces were systematically explored to reveal mechanisms of wetting and boosted flow performances, which are further supported by simulations. Findings of this study highlight that interfacial liquids with lower surface energies, lower viscosities, and higher solubilities can effectively improve water flow without sacrificing rejection performance, achieving by transforming a solid-liquid interface into liquid-liquid interface interaction. It provides a concept to design advanced membrane systems for water purification (e.g., desalination and oil-water separation) and energy conversion processes.

High-flux corrugated PDMS composite membrane fabricated by using nanofiber substrate

Polydimethylsiloxane (PDMS) is a benchmarked membrane material for pervaporation, gas separation, and nanofiltration, remaining challenges in achieving high-flux membrane. Herein, we proposed a high-flux PDMS membrane with corrugated morphology realized by simply coating PDMS solution on nanofiber substrate. It was demonstrated that the electrospun nanofiber substrate with highly interconnected and porous structures could generate a corrugated PDMS membrane layer with highly increased surface area and meanwhile remarkably reduce transport resistance of the membrane. By optimizing the pore structure of nanofiber substrate and reducing the membrane thickness to sub-micrometer, the corrugated PDMS membrane exhibited up to one order of magnitude higher permeation flux compared with state-of-the-arts PDMS membranes for pervaporation separation of ethanol/water mixtures. Specifically, using a 5 wt% ethanol/water mixture as feed at 60 °C, a total flux of 8.7 kg m −2 h −1 and a separation factor of 7.2 were obtained. This work provides a facile approach to develop nanostructured membranes with highly enhanced transport properties. ➢ Corrugated membrane surface is created by coating PDMS on nanofiber substrate ➢ Highly porous and interconnected nanofiber substrate reduce transport resistance ➢ Corrugated PDMS/nanofiber membrane show significantly enhanced pervaporation flux

Rheological properties and wall-slip behavior of cemented tailing-waste rock backfill (CTWB) paste

Cemented tailing-waste rock backfill (CTWB) can effectively improve the ecological environment of the mine. CTWB paste exhibits unique rheological and wall slip characteristics during pipeline transport, which has a significant impact on reducing transport resistance and extending transport distance. A numerical model that integrates material ratio and wall-slip was established by analyzing the rheological test results. COMSOL Multiphysics was used to numerically simulate the paste flow process and output the flow parameters distribution. The results show that CTWB is a yield-plastic fluid, and the shear-thickening phenomenon occurs at 67% and 69% solids content, respectively, and the critical shear rate value gradually increases with the SC. Increasing the coarse aggregate content significantly improves the paste fluidity, and the rheological parameters (plastic viscosity and yield stress) decrease linearly with coarse aggregate content. CTWB paste flow structure has an “equilibrium distance” at which slip velocity starts to stabilize. Tailing-waste rock (T/W) ratio, inlet velocity (IV), and solid content (SC) have a significant effect on the CTWB paste slip behavior. Slip contribution ratio (SR) tends to increase and then decrease with IV, and the process can be described by a quadratic function. Although the SR decreases gradually with the T/W ratio, it can be inferred that the optimal transportation effect is achieved at the T/W ratio is 5:5.

Nonuniformity of Transport Coefficients in Ultrathin Nanoscale Membranes and Nanomaterials.

The quest to reduce transport resistance in separations using nanomaterials has led to considerable interest in nanoscale adsorbents and ultrathin membranes. It is now established that interfacial resistance limits the performance of such nanosized materials; however, the origin of this resistance is uncertain. While it is associated with surface pore blockages and distortions in some materials, its existence even in ideal materials is largely putative. Here, we report equilibrium molecular dynamics (EMD) simulations with ideal zeolite-based nanosheets, indicating the transport resistance to be entirely distributed within the solid, without contribution from an interfacial effect. We demonstrate the presence of an internal entry region over which fluid decorrelation occurs, and in which the local transport coefficient inside the crystal is nonuniform and position-dependent, increasing to the uniform value in the bulk material at larger distances. Our EMD-based diffusivity profiles within the nanomaterial enable us to unequivocally determine the entry length, and reveal an internal excess resistance, frequently assumed to be an interfacial resistance, due to significant reduction of the internal transport coefficient in the entrance and exit regions. A decrease in the entry length with loading in PON zeolite nanosheets is seen. We demonstrate a reduction in external resistance in the external bulk chambers used in simulations, triggered by the interplay of incomplete decorrelation in the nanosheet and periodic boundary conditions imposed on the system comprising the nanosheet and surrounding bulk reservoirs when the nanosheet thickness is less than the entry length. Our analysis of the transport dynamics within the nanosheet demonstrates that, at least for ideal systems, decomposition of the inhomogeneous diffusivity-based internal resistance into an interfacial and a uniform transport coefficient-based internal contribution is not appropriate for finite-sized systems. Our results will enable the improved design of nanoscale membranes and materials for applications in separation and other processes.

Aza[5]helicene Rivals N‐Annulated Perylene as π‐Linker of D−π−D Typed Hole‐Transporters for Perovskite Solar Cells

AbstractThe superior role of helical π‐linkers is demonstrated for the design of donor−π linker−donor typed molecular semiconductors in perovskite solar cells (PSCs). Flat N‐annulated perylene (NP) and contorted aza[5]helicene (A5H) are side‐functionalized with methoxyphenyl and end‐capped with dimethoxydiphenylamine electron‐donor to afford two small‐molecule hole‐transporters J3 and J4. For methoxyphenyl functionalized π‐linkers, intermolecular π⋅⋅⋅π interactions in planar NP exist more extensively than those in helical A5H. However, for the dimethoxydiphenylamine derived hole‐transporters with high highest occupied molecular orbital energy levels, a part of the π⋅⋅⋅π interaction remains for J4 with A5H, while this desirable effect for charge transport is completely deprived for J3 with NP. Thus, the theoretically predicted hole mobility of J4 single‐crystal is even over two times higher than that of J3 one. Because of the larger size of the molecular aggregate, the hole mobility of the spin‐coated J4 thin film is also over three times as high as that of the J3 analog. Due to the reduced transport resistance and enhanced recombination resistance, PSCs with J4 exhibit a power conversion efficiency of 21.0% at standard air mass 1.5 global conditions, which is higher than that of 19.4% with J3 and that of 20.3% with spiro‐OMeTAD control.

UiO-66-NH2 incorporated dual-layer hollow fibers made by immiscibility induced phase separation (I2PS) process for ethanol dehydration via pervaporation

High performance dual-layer hollow fiber membranes have been developed for ethanol dehydration by incorporating a tiny amount (i.e., less than 0.3 wt%) of UiO-66-NH2 particles into cellulose triacetate (CTA)/Ultem® hollow fibers fabricated by the immiscibility induced phase separation (I2PS) process. Effects of particle loading, air gap, feed temperature, feed composition and heat treatment on membrane performance for ethanol dehydration were systematically studied. Positron annihilation spectroscopy (PAS) analyses were conducted to disclose the mechanisms of performance enhancement. Adding UiO-66-NH2 particles improves the permeation flux due to the reduced transport resistance and the enhanced affinity between water and the membranes. The hollow fiber (O-0.2-1.5) consisting of 0.2 wt% UiO-66-NH2 particles in the outer layer possesses the most outstanding separation performance among the newly developed hollow fibers. It has an ultra-high flux of 2667g/m2h (i.e., water permeance of 20.05 mol/m2h kPa) and its permeate comprises 95.00 wt% water, equivalent to a mole-based selectivity of 152 at 50 °C with a feed comprising 85 wt% water and 15 wt% ethanol. After annealing at 120 °C for 2h, the flux drops to 1977 g/m2h but the water concentration in permeate jumps to 98.07 wt%. A comparison with literature data verifies the excellent performance of the newly developed I2PS membranes. The membranes also show impressively stable performance throughout the 200h monitored period for ethanol dehydration. The newly developed membranes may have great potential for pervaporation dehydration of ethanol for industrial applications.

Constructing multidimensional conducting networks on LiCoO2 cathode for enhanced rate performance and cycle stability

The effects of different assemblies of Super P, carbon nanotubes (CNTs) and graphene as hybrid conductive additives on the rate performance and cyclic stability of LiCoO2 (LCO) cathode material were systematically investigated. The results indicated that adding graphene, CNTs or mixture of them into the conventional Super P conductive agent was effective to reduce the overall mass ratio of the carbonaceous conductive additive in the LCO electrode while significantly improving the rate performance and cycle stability. The best electrochemical performance was achieved on the electrode with 1 wt% (G + SP) and 1 wt% CNTs. Microstructural investigations indicated that a multidimensional conducting network had been constructed within this cathode, which provided efficient electronic and ionic transportation pathways, as evidenced by the reduced transport resistance and improved Li-ion diffusion dynamics. With this composition, a high discharge capacity of 118 mA h g−1 was obtained at a current density of 10 C (1400 mA g−1), and a high capacity retention of 92.3% was maintained after 100 cycles at 1 C.

Influence of Morphology on Transport Properties and Interfacial Resistance in Nanoporous Carbons

The drive for enhancing process efficiency by decreasing the system length scale to reduce transport resistance in nanomaterials brings into prominence the interfacial resistance, the relative impo...

Mixed-matrix carbon molecular sieve membranes using hierarchical zeolite: A simple approach towards high CO2 permeability enhancements

Membrane process is a robust technology for CO2/CH4 separation. To achieve the energy-efficiency necessary for a cost-effective membrane-based CO2/CH4 separation, high-performance membranes are often desirable. There are several approaches that can be undertaken to realize such membranes. In this study, we amalgamated three strategies: 1) filler design optimization by synthesizing hierarchical zeolite 5A comprising micro and mesoporous domains to strengthen the second strategy; 2) mixed-matrix approach by incorporating zeolite fillers to facilitate CO2 diffusion and reduce transport resistance through a Matrimid® matrix; and 3) membrane carbonization to induce thermal rearrangement, and create free volumes and pore apertures for a faster CO2 transport. These efforts afforded mixed-matrix carbon molecular sieve membranes with results confirming that our membrane at 30 wt% loading of hierarchical zeolite 5A was able to surpass the 2008 Robeson upper bound limit given a performance of 2450 barrers CO2 permeability and 19.3 CO2/CH4 selectivity. Notably, at this loading, the negative effect brought by the interfacial nanogaps between the filler and carbon matrix diminished, unleashing the potential of the mesopores in facilitating CO2 diffusion, which led to a two orders of magnitude enhancement in the CO2 permeability relative to the unfilled carbon molecular sieve membrane. Despite a decrease in the CO2/CH4 selectivity, the hierarchical zeolite 5A is effective in alleviating the intensity of the permeability-selectivity trade-off. Also, benchmarking of the filler effectiveness is first demonstrated using a new filler enhancement index, Findex. The largest Findex value in this study was 1.97. This attaches a label of “competent” to our hierarchical zeolite 5A filler at 30 wt% loading, demonstrating the success of our strategies.

Fuel Cell Electrodes Based on Functional Meso-Structured Arrays

State-of-the-art fuel cell catalyst layers consist of a random mixture of functional components (catalyst, ionomer, and pore) that are formed in an uncontrolled ink deposition process. The random nature of these structures makes it difficult to optimize the functional domains and hence causes severe mass transport limitations during high-power operation, resulting in a loss in performance and requiring that the fuel cell be oversized to maintain an acceptable level of performance. The ionomer binder adds an additional transport resistance and becomes significant at lower Pt loadings [1]. Decreasing this transport resistance would remove the main barrier to low-cost, ultra-high power density fuel cells. Rational design of the electrode structure in PEFCs could improve performance and reduce cost. By separating the different electrode functions into discrete electrode elements, each element can be optimized for specific functions. Arranging these optimized discrete elements in a controlled, low-tortuosity array configuration enables transport limitations to be reduced or eliminated. We have demonstrated this approach through fabrication of freestanding arrays of vertically-oriented ionomer channels with different aspect ratios, and incorporation of these channels into fuel cell electrodes where they serve as non-tortuous proton-transport highways (Figure 1). Providing effective proton transport through these low-tortuosity percolating highways allows the catalyst domain to have a lower ionomer/catalyst ratio, reducing transport resistance. Proof of concept was demonstrated by achieving a 15% increase in performance with channels with an aspect ratio of 8. Further work is underway to increase channel aspect ratio and improve integration of channels with surrounding catalyst layer, leading to further transport improvements and increases in performance. Fig. 1. Left: freestanding array of ionomer channels. Right: catalyst layer incorporating ionomer channels. References N. Nonoyama, S. Okazaki, A. Z. Weber, Y. Ikogi, and T. Yoshida, J. Electrochem. Soc., 158, B416 (2011). Acknowledgments This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium. Figure 1

New modules for membrane bioreactors: Improving fouling control

New hollow fiber membrane modules with air injectors coupled to their base are presented in this paper. The transport resistances were analyzed through permeation tests with yeast cells suspensions varying parameters such as surface air velocity and filtration pressure. Five different modules were investigated, and the lowest resistances were observed in the module with 64 holes in the air injector and packing density equal to 650m2m−3. The modules with 32 holes in the air injector and packing density of 650m2m−3 showed the best relation between the efficiency in reducing transport resistance and the aeration energy expenditure.

Maintenance of carbohydrate transport in tall trees.

Trees present a critical challenge to long-distance transport because as a tree grows in height and the transport pathway increases in length, the hydraulic resistance of the vascular tissue should increase. This has led many to question whether trees can rely on a passive transport mechanism to move carbohydrates from their leaves to their roots. Although species that actively load sugars into their phloem, such as vines and herbs, can increase the driving force for transport as they elongate, it is possible that many trees cannot generate high turgor pressures because they do not use transporters to load sugar into the phloem. Here, we examine how trees can maintain efficient carbohydrate transport as they grow taller by analysing sieve tube anatomy, including sieve plate geometry, using recently developed preparation and imaging techniques, and by measuring the turgor pressures in the leaves of a tall tree in situ. Across nine deciduous species, we find that hydraulic resistance in the phloem scales inversely with plant height because of a shift in sieve element structure along the length of individual trees. This scaling relationship seems robust across multiple species despite large differences in plate anatomy. The importance of this scaling becomes clear when phloem transport is modelled using turgor pressures measured in the leaves of a mature red oak tree. These pressures are of sufficient magnitude to drive phloem transport only in concert with structural changes in the phloem that reduce transport resistance. As a result, the key to the long-standing mystery of how trees maintain phloem transport as they increase in size lies in the structure of the phloem and its ability to change hydraulic properties with plant height.

Meso-Structured Array Electrode for Polymer Electrolyte Fuel Cells

Current state-of-the-art fuel cell cathodes rely on high loading of platinum (Pt) or Pt-alloy on high surface area carbon supports mixed with Nafion. The cost of the high Pt loading is still a hindrance to the commercialization of polymer electrolyte fuel cells (PEFCs) 1. The electrode structure consists of a random aggregation of the functional components (catalyst, ionomer, and pore space) that are formed in an uncontrolled ink deposition process. The random nature of these structures makes it difficult to optimize the functional domains and hence causes severe mass transport limitations during high-power operation, resulting in a loss in performance and requiring a higher loading and active area of Pt to maintain an acceptable level of performance. The ionomer binder adds an additional transport resistance and becomes significant at lower Pt loadings2. Decreasing this transport resistance would remove a significant barrier to low-cost, ultra-high power density fuel cells. Rational design of the electrode structure in PEFCs could improve performance and reduce cost. However, in current state-of-the-art fuel cells, each unit volume of electrode contains a random mix of components that must simultaneously provide catalytic activity, water transport, O2transport, electronic conductivity, and protonic conductivity. Since each unit must provide all functions, units cannot be optimized for individual functions. By separating the different electrode functions into discrete electrode elements, each element can be optimized for specific functions as shown in Figure 1a. Arranging these optimized discrete elements in a controlled, low-tortuosity configuration enables transport limitations to be reduced or eliminated. In previous work, Middlemen et al. showed under optimal conditions oriented catalyst layer structure can be fabricated but didn’t present any electrochemical evaluation 3. Komini Babu et al. fabricated vertically oriented Nafion nanofibers and deposited Pt via vapor deposition 4. The Nafion nanofiber electrode showed increase in performance compared to Pt sputtered on Nafion 115 electrode but lower in performance to Pt/C based electrode. In this work, we propose an alternate electrode structure to enable good transport behavior and high cell performance through controlled deposition of electrode components in an optimized, organized structural configuration. Figure 1b shows the SEM image of Nafion nanofibers for proton transport, fabricated by solution casting on a porous template. Providing effective proton transport through these low-tortuosity percolating highways allows the catalyst domain to have a lower ionomer/catalyst ratio, reducing transport resistance. Acknowledgments This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos.