Cathode Gas Diffusion Layer Research Articles

Simultaneous accelerated stress testing of membrane electrode assembly components in polymer electrolyte fuel cells

The durability of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles is important for the shift from passenger cars to heavy-duty vehicles. The components of a PEFC, namely the proton exchange membrane (PEM), catalyst layer (CL), and gas diffusion layer (GDL), contribute to the degradation of the fuel cell performance. In this paper, we propose a method for simultaneously evaluating the degradation rates of these components by combining electrochemical characterization with operando synchrotron X-ray radiography. The open-circuit voltage, electrochemically active surface area (ECSA), and water saturation were used as the degradation indicators for the PEMs, CLs, and GDLs, respectively. The results of two accelerated stress tests (loading and start-stop cycles) after 10,000 cycles showed that the increase in water saturation owing to the loss of hydrophobicity due to carbon corrosion in the cathode GDL occurred on the same timescale as the degradation in the PEM and cathode CL. Specifically, during the load cycle AST, the cathode CL degraded with a 26% reduction in the ECSA along with the cathode GDL degradation with a 10% increase in water saturation. This suggests that more efforts should be devoted to studies on the durability of GDLs for heavy-duty applications.

Two-Phase Fluid Dynamics in Proton Exchange Membrane Fuel Cells: Counter-Flow Liquid Inlets and Gas Outlets at the Electrolyte-Cathode Interface

Understanding the counter-flow of liquid inlet and gas outlet at the interface between the electrolyte and cathode gas diffusion layer (GDL) is crucial for water management in proton exchange membrane fuel cells. Existing studies typically overlook air outlets and assume a fixed liquid inlet direction. This study uses a volume of fluid method to model two-phase interactions in a T-shaped GDL and gas channel (GC) assembly, with GDL geometry derived from nano-computer tomography. Considering potential electrode deformations, such as local cracks and blockages, this research investigates the impact of the size and shape of liquid invasion on the liquid-gas behavior in the cathode GDL and GC using five liquid injection configurations. Simulations also incorporate GDL gas outlets, integrating them with a tailored liquid inlet setup. Results show that the injection site and configuration significantly affect water behavior in the GDL, affecting saturation, stabilization, and breakthrough, followed by drainage in the GCs. Comparisons of simulations with and without air outflow show distinct counter-flow interactions, highlighting variations in water distribution and discrepancies in two-phase transport across the GCs.

Effects of Sodium Chloride on PEMFC Durability at a Concentration Close to that of a Marine Environment

The marine application of proton exchange membrane fuel cells (PEMFCs) requires special attention due to sea salt aerosols and atmospheric pollutants, susceptible to degrade these systems and induce performance losses. To the best of our knowledge, this study is the first to identify the performance losses of PEMFCs due to sodium chloride (NaCl) pollution similar to that of the marine environment. A 641 h ageing test with a NaCl concentration in air of 120 μg.m‒3 was carried out on a five cells stack of 220 cm2. The results reveal a key mechanism for reversible performance loss, namely the deposition of salt particles in the channels and on the surface of the cathode gas diffusion layer (GDL). This can lead to the complete shutdown of a cell. Nonetheless, this contamination did not induce significant irreversible performance losses as the restarts of the stack cause the salt particles to dissolve. An overall degradation rate of 8 μV·h‒1, similar to that of the baseline without NaCl contamination, is observed.

Porosity and permeability optimization of PEMFC cathode gas diffusion layer based on topology algorithm

The gas diffusion layer (GDL) is a crucial component in proton exchange membrane fuel cells (PEMFCs), significantly affecting mass transport and overall cell performance. Due to the pronounced pressure gradients and uneven mass transfer between the inlet and outlet of the serpentine flow field, this study proposes the design of a GDL with a concentration gradient to optimize performance. Leveraging topological optimization algorithms, the research focuses on enhancing the mass transport properties and improving cell efficiency. The optimization process considers the pressure distribution, oxygen concentration, and water content within the serpentine flow field as boundary conditions. By optimizing the porosity and permeability of the GDL in different regions, the study aims to enhance the GDL's mass transport capabilities. Simulation results demonstrate that initializing the porosity at 1 provides superior optimization, significantly enhancing mass transfer and overall cell performance. Although increased permeability contributes to improved mass transport, its impact is less significant compared to porosity optimization. Therefore, GDL porosity is identified as the dominant factor in enhancing cell performance, while permeability adjustments play a secondary role.

Asymmetric gas diffusion layers for improved water management in PGM-free electrodes

Proton-exchange-membrane fuel cells (PEMFCs) offer a long-term, carbon-emission free solution to the energy needs of the transportation sector. However, high cost continues to limit PEMFC commercialization. Replacing expensive platinum group metal (PGM) catalysts with PGM-free catalysts could reduce cost, but the low active site density of PGM-free catalysts necessitates the use of thick electrodes that suffer from substantial mass transport losses. In these thick PGM-free electrodes, effective water management and oxygen transport are crucial to achieve high performance. In this work, we investigate the role of anode and cathode gas diffusion layer (GDL) configurations in controlling water management. Asymmetric GDL configurations, in which the anode GDL exhibits higher permeability than the cathode GDL, showed higher performance compared to conventional symmetric configurations. Computational modeling showed that the improved performance is mainly due to improved water management, resulting in lower liquid water saturation and faster oxygen transport in the cathode.

Effect of fiber curvature on gas diffusion layer two-phase dynamics of proton exchange membrane fuel cells

Both straight and curved carbon fibers are widely used in various commercial gas diffusion layer (GDL) fabrications. The effect of the different carbon fiber curvatures on two-phase flow dynamics within the cathode GDLs of proton exchange membrane fuel cells remains unclear. In this study, we investigate liquid transport in three types of GDLs with varying fiber curvatures using the two-phase volume of fluid simulations in OpenFOAM. For the first time, a rod periodic surface model is combined with a layer-by-layer fiber stacking strategy, to stochastically reconstruct GDL structures while incorporating crucial parameters from physical (experimental) GDLs. A grid independence study and model validation are conducted. Following pore network analysis of pore size distribution and connectivity, we study the time-varying GDL total and local water saturation and capillary pressure. Despite maintaining similar layer and bulk porosity, increased fiber curvature enhances pore connectivity but raises water saturation and capillary pressure, increasing the risk of flooding. Additionally, droplets in gas channels with straight-fiber GDLs are larger and have slower movement than those in curved-fiber GDLs. Fiber curvature inversely affects drainage capacity in GDLs and connected channels. With comparable water saturation and capillary pressure, curved-fiber GDLs exhibit lower discrepancies, suggesting improved uniformity in water distribution.

Numerical Simulation of Effects of Catalyst Layer Parameters on Heat Transfer in Proton Exchange Membrane Fuel Cells

A non-isothermal, two-dimensional, two-phase fuel cell agglomerate model is used, and studies are done on how platinum loading and catalyst layer thickness affect heat transfer in fuel cells. Results indicate that as the cathode platinum content and catalyst layer (CL) thickness rise, the electrical property is improved. The maximum power density corresponding to the platinum loading of 0.40 mg/cm2 increases by 8.92% compared with 0.20 mg/cm2, and the maximum power density corresponding to the CL thickness of 17.5 µm increases by 4.63% compared with 10.0 µm. Temperature variation trends in CLs from entry to exit and inside the cell along the thickness direction do not change. Furthermore, with the CL thickness as well as platinum content increasing, the temperature increment inside cathode gas diffusion layer as well as CL is more obvious, and temperature distribution uniformity within the cell deteriorates. The impact of platinum loading on the temperature in the cell is more obvious than that of CL thickness. In the selection about platinum content and thickness of CL, temperature distribution uniformity and electrical property should be weighed.

Comprehensive Analysis of Wettability in Waterproofed Gas Diffusion Layers for Polymer Electrolyte Fuel Cells.

In polymer electrolyte fuel cells (PEFCs), the gas diffusion layer (GDL) is crucial for managing the flooding tolerance, which is the ability to remove the water produced during power generation from the assembled cell. However, an improved understanding of the properties of GDLs is required to develop effective waterproofing strategies. This study investigated the influence of the polytetrafluoroethylene (PTFE) content on the pore diameter, porosity, wettability, water saturation, and flooding tolerance of waterproofed carbon papers as cathode GDLs in PEFCs. The addition of minimal PTFE (∼6 wt %) to carbon paper provided external waterproofing, whereas internal waterproofing was achieved at a higher PTFE content (∼13 wt %). However, excessive PTFE (∼37 wt %) led to macropore collapse within the carbon paper, reducing fuel cell performance. Although PTFE addition was expected to improve the flooding tolerance, operando synchrotron X-ray radiography revealed that the water saturation level in carbon paper increased with increasing PTFE content. These findings provide a benchmark for assessing whether GDLs meet the flooding tolerance requirements of PEFCs and may be applicable to waterproofed GDLs in electrochemical devices for water and CO2 electrolysis.

Liquid Water Visualization in the Pt‐Loading Cathode Catalyst Layers of Polymer Electrolyte Fuel Cells Using Operando Synchrotron X‐ray Radiography

Water management is important for addressing the challenges posed by next‐generation fuel cell electric vehicles. Although X‐ray imaging techniques are useful for probing the mechanism of water transport in the gas diffusion layer of polymer electrolyte fuel cells, they cannot be easily applied to the Pt‐loading catalyst layer because of its low X‐ray transmittance due to the high absorption coefficient of Pt. Herein, a method to realize the high‐resolution X‐ray imaging of a 30 μm‐thick cathode catalyst layer in polymer electrolyte fuel cells using synchrotron X‐ray radiography is proposed, thus bridging the above gap. The results of operando synchrotron X‐ray radiography measurements reveal that water accumulation in the cathode catalyst layer depends on the cell temperature, feed gas humidity, and cell voltage, while time‐slice analysis shows that the water accumulation rate in the cathode catalyst layer immediately after the power generation is faster than that in the cathode gas diffusion layer. The proposed imaging method can be used to evaluate the water storage capacity of the catalyst layer and thus deepen the understanding of flooding phenomena and cold‐start behavior at subzero temperatures.

Operando X-ray radiography of liquid water distribution in 100 mm polymer electrolyte fuel cell channels

Preventing the accumulation of water in the gas diffusion layer (GDL) proves effective in enhancing the performance of polymer electrolyte fuel cells (PEFCs). To understand the water transport phenomena in GDLs and channels of PEFCs, cell hardware for operando synchrotron X-ray radiography was developed with a 100 mm channel length, facilitating the separate quantification of liquid water in the cathode and anode GDLs. The presence of liquid water in the cathode and anode GDLs was confirmed during operation with a supply of dry gas in a counter-flow configuration. Furthermore, the amount of liquid water in the cathode and anode GDLs increased toward the cathode inlet, while the amount of water in the cathode and anode channel regions increased toward each outlet. The liquid water distribution in the GDLs along the channel direction can be attributed to water transport from cathode to anode (back-diffusion), decreasing toward the anode outlet. Therefore, conducting radiography experiments aligned parallel to the GDLs and perpendicular to the channel could provide valuable insights for a more comprehensive understanding of water transport in cells.

Examining Invasion‐Percolation Across the Cathode Layered Assembly in Polymer Electrolyte Membrane Fuel Cells: Oxygen Resistance, Wettability and Cracks

AbstractEfficient evacuation of water generated by oxygen reduction reaction is necessary to increase catalyst utilization in polymer electrolyte membrane Fuel Cells. However, analysis of two‐phase transport is challenged by the wide range of pore sizes present in the membrane electrode assembly (MEA), varying from 10–100 nm in the catalyst layer (CL), 10–1000 nm in the microporous layer (MPL) and 10 μm in the gas diffusion layer (GDL). In this work, a novel multiscale invasion‐percolation model accounting for the cathode CL, MPL and GDL is presented. Saturation in the macroporous GDL is modeled through an all‐or‐nothing invasion law (empty/filled), while a macroscopic description in terms of the capillary pressure curve is adopted for the MPL and the CL. The oxygen transport resistance across the cathode MEA is quantified using the computed saturation distributions. Among other conclusions, the results show that MPL addition is crucial to avoid local flooding at the CL/GDL interface, providing localized access points to the GDL rather than massively invading interfacial macropores. However, excessive MPL hydrophobicity can cause CL flooding. Water removal from the CL can be enhanced by using a more hydrophilic MPL, a hydrophobic CL or the addition of a moderate volume fraction of cracks. Oxygen transport can be further improved by modulating the arrangement of water in the GDL with patterned wettability, provided that the number of MPL cracks is low.

Coupled optimization of auxiliary channels and porosity gradient of GDL for PEMFC

In this study, we proposed a novel under-rib auxiliary channel and developed a systematic methodology combining computational fluid dynamics (CFD), an artificial neural network (ANN), and a particle swarm optimization (PSO) algorithm for the coupled optimization of the auxiliary-channel structure and gas diffusion layer (GDL) porosity gradient in a proton exchange membrane fuel cell (PEMFC). First, we developed a three-dimensional multiphase numerical model of a non-isothermal parallel flow-field PEMFC. ANN was then applied to obtain a mapping relationship between auxiliary channels structure, GDL porosity gradient and output performance of PEMFC with finite CFD data. Finally, PSO was employed to perform an optimization search to determine the optimal parameter pairing, resulting in a 16.7 % increase in maximum power density and a 20.6 % increase in the current operating range. In addition, the optimized PEMFC exhibited superior mass transfer and water removal capabilities, where the average oxygen concentration in the intermediate section of cathode GDL was increased by 33.3 % and the maximum liquid water saturation was reduced by 23.5 %. Moreover, the coupled optimization of the auxiliary channels and the GDL porosity gradient can increase power density by at least 8.7 % and current density by 9.1 % compared to single component optimization.

Two-phase flow in the gas diffusion layer with different perforation of proton exchange membrane fuel cell

ABSTRACT Gas diffusion layer (GDL) is an important pathway for water transport in the proton exchange membrane fuel cell. The presence of excessive liquid water in the cathode GDL will cause “water flooding” and block the reactant transport path to catalyst sites. Therefore, it’s critical to understand water transfer mechanism in GDL and propose novel strategy to improve water management. In this study, the effect of GDL with different perforation holes on liquid water transport behavior are investigated by volume of fluid method. The simulation model is validated by comparing with the reported data. The results show that the GDL with perforation holes will accelerate the liquid water breakthrough. Specially, the GDL with cylindrical perforation achieves the lowest breakthrough pressure, and most excellent water drainage capacity under various pressure drops. The gradient hydrophobic distribution in GDL will improve the water breakthrough path and drainage capacity. However, gradient hydrophobic treatment in GDL with conical perforations will result more water leakage along the though-plane direction. The simulation results will provide significant guidance for designing high performance GDL and improving the water management in proton exchange membrane fuel cell.

Comparative study on carbon corrosion characteristics of gas diffusion layer in PEMFCs under two accelerated stress tests

As a key component of proton exchange membrane fuel cell, the durability of gas diffusion layer (GDL) is directly related to the overall life of fuel cell. Carbon corrosion is a critical factor influencing the durability of GDL, damaging its pore structure and reducing its hydrophobicity, thus affecting the internal water management of fuel cells. At present, although there are many accelerated stress testing (AST) methods for studying carbon corrosion, there is a lack of indicators between these methods to comprehensively compare and analyze the corrosion of GDL. Herein, two ASTs, i.e., steady-state durability testing at a constant-potential of 1.4 V (vs. RHE) and dynamic testing of a voltage triangular-wave of 1–1.5 V (vs. RHE), are used to assess the durability of cathode GDL. The results reveal that the variation rates of pore volume and hydrophobicity of GDL after 6000 cycles of triangular-wave AST are faster than those after 24 hours of constant-potential AST. By comparing the variation rates of oxygen mass transfer resistance and mass transfer impedance (Rmt) of GDL, it is found that the corrosion rate of triangular-wave AST is 6.75 times higher than that of constant-potential AST under the same corrosion degree.

Effects of gas diffusion layer thickness on PEM fuel cells with composite foam-rib flow fields

Gas diffusion layers (GDLs) play a crucial role for the performance of proton exchange membrane fuel cells (PEMFCs). The utilization of composite foam-rib flow fields (CFRFFs) can alter the reactant gas transfer pattern, hence improving the efficiency of under-rib reactant gas transfer and water drainage. The impact of the cathode and anode GDL thicknesses (hc,GDL and ha,GDL) on the performance of CFRFF design is investigated by three-dimensional multiphase non-isothermal numerical simulation in this study. The results indicate that for the conventional rib flow field (CRFF) design, there is an optimal hc,GDL for optimal cell performance, while for the CFRFF design, as hc,GDL becomes thinner, the cell performance increases, and the trend is dominated by the variation of the oxygen concentration. Under a thin GDL, the rib width of the CRFF design should be as small as possible to minimize concentration polarization loss, while the rib width of the CFRFF design can be slightly larger. Furthermore, by decreasing the thickness of ha,GDL in both the CRFF and CFRFF designs, there is an increase in the dissolved water content in the ionomer of the cathode CL and a subsequent decrease in the Ohmic polarization loss.

Effects of cathode gas diffusion layer porosity and contact angle distributions along through-plane direction on the performance of polymer electrolyte membrane fuel cell

In the present work, a numerical model for polymer electrolyte membrane fuel cell (PEMFC) has been employed to investigate the effects of porosity and contact angle distributions of the porous layer on the performance of PEMFC. The three-dimensional, two-phase, and non-isothermal flow solver considers heat transfer, electrochemical reaction, and liquid water saturation. Various cases with different cathode gas diffusion layer (GDL) porosities are performed. The results showed that a better performance is achieved when the GDL porosity is increased because of the reduced mass transport resistance of oxygen. The effects of the porosity distributions on the PEMFC performance were examined by comparing the predictions from the cases with non-uniform porosity and uniform porosity in the cathode GDL. It was shown that the current density of the cases with non-uniform porosity is higher than that of the uniform porosity case when the operation voltage is low. This is due to the fact that non-uniform porosity distributions in the cathode GDL enhance the reactant transport. When the operation voltage is high, the current densities of the cases with non-uniform porosity and uniform porosity are almost the same. Moreover, the influence of contact angle distributions in cathode GDL was explored. Various cases with gradient-decreasing, gradient-increasing, and uniform constant contact angles from GDL/channel interface to GDL/catalyst layer interface were studied. It was found that the case with gradient-increasing contact angle has a better performance due to the larger capillary pressure difference to remove more water. The poor performance of the case with gradient-decreasing contact angle is related to the phenomenon of flooding in the catalyst layer.

Development and Evaluation of the Joining Process of Gas Diffusion Layer and Membrane Electrode Assembly for PEM Fuel Cells

To achieve the goal of decarbonizing the heavy-duty transport sector, polymer electrolyte membrane (PEM) fuel cells need to be commercialized, and manufacturing processes must be optimized to meet the demands of industrial upscaling. By joining the anode and cathode gas diffusion layers (GDL) to the 5-layer membrane electrode assembly (MEA), the number of repeating units for the subsequent stacking process can be reduced from four to two. Hence, the stacking process time based on pick-and-place operations can be reduced by almost half. In the joined state, the relatively rigid GDL can also protect the fragile CCM from potential material damage caused by handling processes during stacking. Both literature and patent screening were conducted on possible joining options between the GDL and the 5-layer MEA. A low viscosity UV-activated adhesive was selected for the systematic investigation of the joining process. In order to achieve a highly precise and repeatable adhesive dispensing process within the scope of a roll-to-roll (R2R) MEA assembly system, a semi-automatic test rig was designed and built to bond the GDL to the 5-layer MEA. Various criteria for evaluating adhesive joint were analyzed and pre-selected, taking into account the economic factor, the quality of the joint, and the influence on downstream processes. A pre-activation strategy was deployed to successfully compensate for the adhesive absorption effect of the GDL due to its porous structure. A parameter combination of mass flow rate, joint design, applied pressure and curing strategy was found, where the adhesive bond between the GDL and the subgasket was sufficient for further manufacturing processes. With the developed joining process and the test rig, it is possible to create industrial process-like conditions and transfer the results to an industrial R2R MEA assembly process.© 2024 The Authors, Published by Elsevier B.V.5

In situ 3D X-ray imaging of water distribution in each layer of a membrane electrode assembly of a polymer electrolyte fuel cell.

In situ 3D computed tomography imaging with statistical analysis successfully revealed the water accumulation and drainage characteristics in the stacked gas diffusion layers (GDLs) and membrane electrode assembly (MEA) of a polymer electrolyte fuel cell. Efficient water drainage at the interface between the cathode GDL and MEA was confirmed upon supplying oxygen to the cathode.

Numerical Simulation of Local Entropy Generation of Oxygen Transport in Cathode Diffusion Media of PEFC

To further improve the power density and efficiency of polymer electrolyte fuel cells (PEFCs), it’s necessary to review the conventional flow fields consisting of porous electrodes and gas channels and reduce the overpotentials due to the electrochemical reaction and mass transport. In the past works, the voltage loss in fuel cells had been generally classified into the activation, ohmic and concentration polarizations and evaluated comprehensively. However, the factors of the energy loss should be identified in more detail to design the better electrode/channel structure, because the interaction of the heat and mass transfer, ionic and electronic transport and electrochemical reaction occurs complicatedly in porous electrodes. Several researchers [1-2] focused on entropy that is a physical property representing the thermodynamic irreversibility and evaluated the energy losses in fuel cells and electrochemical devices from the view of entropy generation. Especially, Charoen-amornkitt et al. [2] has attempted to design the diffusion field in a reaction-diffusion system with the use of a combination of entropy generation analysis and topology optimization. The analysis of entropy generation enables to identify the dominant process causing the overpotential in PEFCs and contributes to design the optimum electrode/channel structure minimizing the energy loss. This study introduced the evaluation technique using entropy generation into the conventional two-phase flow simulation for the gas diffusion layer (GDL) of a PEFC and succeeded to numerically estimate the distribution of entropy production rate due to the oxygen diffusion in the cathode GDL. Furthermore, the author investigated the effect of land-channel configuration on the local entropy generation of oxygen transport within the GDL in detail and discussed how to design the electrode/channel structure reducing the entropy generation.Fig. 1 presents the numerical results of the two-phase flow simulation and the entropy generation analysis in the cathode GDL. The two-phase model used in this study was developed by Natarajan and Nguyen [3]. The model domain consists of the flow channel, both lands, GDL and catalyst layer in the cross section of the cathode. Figs. 1(a) and 1(b) denote the distributions of the oxygen concentration (mole fraction) and the entropy production rate due to the oxygen diffusion, respectively. In the simulation, the fuel cell was operated for 200 s at the temperature of 80 oC and the constant current density of 1.0 A/cm2. The pressure and humidification of air supplied to the cathode were set to 1 atm and 80 %RH. As shown in Fig. 1(a), the oxygen concentration is lowered under the land because of its insufficient supply. The result of entropy generation analysis in Fig. 1(b) revealed that the entropy production rate due to the oxygen diffusion becomes remarkably high under the boundary between the flow channel and land that causes its large concentration gradient. To reduce the entropy generation in this area, it’s necessary to design the electrode/channel structure alleviating the gradient of oxygen concentration.

Control of Liquid Water Transport in Cathode of PEFC Using Wettability-Patterned Electrodes

During the operation of polymer electrolyte fuel cells (PEFCs), the product water that accumulates in the cathode electrode blocks the oxygen transport to the reaction sites and causes severe performance degradation. This phenomenon, known as “flooding,” is one of the critical issues to be solved for achieving high efficiency and high power density. To alleviate water flooding, it’s necessary to design an electrode/channel structure that could actively remove liquid water from the porous electrode. Zhang et al. [1] reported that the wettability patterning of a gas diffusion layer (GDL) enables it to provide the liquid water pathway in the cathode electrode. Furthermore, Nishida et al. [2] demonstrated that the hydrophilization of cathode channel walls promotes water removal from the GDL to the flow channel. This study fabricated a wettability-patterned GDL impregnated with a hydrophilic silica-based solvent and newly proposed an electrode/channel structure combining the patterned electrode and hydrophilized flow channel. The effect of its structure on the liquid water distribution within the cathode GDL of an operating PEFC was also investigated using X-ray imaging.The authors fabricated the experimental fuel cell with an effective electrode area of 1.8 x 1.6 cm2. The membrane electrode assembly (MEA) was sandwiched between two carbon separators with a single-serpentine flow field (number of channels: 7, channel width: 1.0 mm, depth: 1.0 mm, total length: 88.5 mm). Fig. 1 shows the regions measured by X-ray imaging in the cross-sectional view of the cathode. Since the cathode GDL is irradiated with an X-ray beam in the in-plane direction, the through-plane distributions of water can be observed in the GDL. The measurement regions were set under the 4th channel and under the land between the 3rd and 4th channel. The GDL in the cathode was impregnated with the silica-based solvent in the range of 0.3 mm width x 10 mm length x 0.1 mm depth. The hydrophilized region was positioned along the right sidewall of the 4th channel. The channel walls of the cathode were also coated with the same hydrophilic solvent. Fig. 2 represents the distribution of water saturation in the (a) uncustomized and (b) wettability-patterned GDL. The current density was increased stepwise from 0.14 to 1.02 A/cm2 for 8 min at room temperature and non-humidified condition. All images were captured at t=6 min after starting the operation. Dry hydrogen (stoichiometry: 1.5@2.0A/cm2) and oxygen (stoichiometry: 3.0@2.0A/cm2) were supplied to the anode and cathode, respectively, in a counter-flow arrangement. As shown in Fig. 2(b), it was noted that the water saturation around the hydrophilized region was effectively reduced due to the in-plane water suction. The patterned GDL partially impregnated with the highly hydrophilic solvent enables to induce the product water from the hydrophobic to hydrophilic region, resulting in the reduction of flooding. To further accelerate the through-plane water transport from the hydrophilized region in the GDL to the channel sidewall, it’s essential to introduce a difference in their wettability and optimize their combinations.