Ionic Conductivity over Metal/Water Interfaces in Ionomer‐Free Fuel Cell Electrodes

Hu, Leiming; Zhang, Muxing; Babu, Siddharth Komini; Kongkanand, Anusorn; Litster, Shawn

doi:10.1002/celc.201900124

Cited by 15 publications

(10 citation statements)

References 42 publications

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“…Recently, a proton conduction mechanism at the surface of an ionomer‐free Pt electrode was proposed ( Figure a). [ 177 ] The proton conduction properties were observed via the surface‐adsorbed water film on the extended Pt electrode. It was postulated that the conductivity in the lower potential region is related to H adsorption on the surface, while the conductivity in the higher potential region is related to the oxide coverage, H adsorption enables proton transport in the low potential regimes, while the surface oxide results in a negatively charged surface at high potential regimes that provide the proton conduction pathway.…”

Section: Optimization Of 3d Pt Architectures For High‐performance Fuementioning

confidence: 99%

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Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

Kim

et al. 2020

Advanced Materials

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oxidizing agent (oxygen). [4,5] Fuel cells are considered likely by many to play a central and integral role in future renewable energy developments. However, reducing their cost has been a significant challenge, and is critical for promoting future studies and accelerating market growth. [6-8] Currently, noble Pt materials are the most favored electrocatalysts for the electrochemical reactions at both the anode and cathode in fuel cells. The cathodic oxygen reduction reaction (ORR) rate is substantially slower than the anodic hydrogen oxidation reaction by several orders of magnitude. When properly tailored in electrodes, Pt materials provide fast reaction kinetics, good electrical conductivity, and high chemical stability in strongly acidic electrolytes. [9-11] Conventional electrocatalyst structures generally employ fine Pt powders (2-3 nm) supported on high surface area carbon (Pt/C). However, as the number of large scale energy applications continues to increase, the high required Pt loading (typically ≈0.5 mg cm −2 for commercial electrodes) and high cost of this precious metal (≈$1000 per troy ounce) pose significant barriers to the widespread use of fuel cells containing Pt materials. The quantity of Pt required to achieve the targeted electrode performance significantly contributes to the high cost of fuel cell systems. [12-14] In recent decades, significant efforts have been devoted to investigating the principles underlying the electrocatalyst layer, A new direction for developing electrocatalysts for hydrogen fuel cell systems has emerged, based on the fabrication of 3D architectures. These new architectures include extended Pt surface building blocks, the strategic use of void spaces, and deliberate network connectivity along with tortuosity, as design components. Various strategies for synthesis now enable the functional and structural engineering of these electrocatalysts with appropriate electronic, ionic, and electrochemical features. The new architectures provide efficient mass transport and large electrochemically active areas. To date, although there are few examples of fully functioning hydrogen fuel cell devices, these 3D electrocatalysts have the potential to achieve optimal cell performance and durability, exceeding conventional Pt powder (i.e., Pt/C) electrocatalysts. This progress report highlights the various 3D architectures proposed for Pt electrocatalysts, advances made in the fabrication of these structures, and the remaining technical challenges. Attempts to develop design rules for 3D architectures and modeling, provide insights into their achievable and potential performance. Perspectives on future developments of new multiscale designs are also discussed along with future study directions.

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Section: Optimization Of 3d Pt Architectures For High‐performance Fuementioning

confidence: 99%

Section: Optimization Of 3d Pt Architectures For High‐performance Fuementioning

confidence: 99%

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

Kim

et al. 2020

Advanced Materials

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“…As the operating temperature of a PEMFC is lower than other types of fuel cell, the water generated in the catalytic layer (CL) may exist in liquid form. Water is essential for PEMFCs, because protons can only efficiently cross the membrane when it is sufficiently hydrated [ 4 ]. However, there is also has a negative impact on cell performance when the liquid water in the membrane electrode assembly (MEA) is excessive [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

Effects of Cathode GDL Gradient Porosity Distribution along the Flow Channel Direction on Gas–Liquid Transport and Performance of PEMFC

et al. 2023

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The gas diffusion layer (GDL) is an important component of proton exchange membrane fuel cells (PEMFCs), and its porosity distribution has considerable effects on the transport properties and durability of PEMFCs. A 3-D two-phase flow computation fluid dynamics model was developed in this study, to numerically investigate the effects of three different porosity distributions in a cathode GDL: gradient-increasing (Case 1), gradient-decreasing (Case 3), and uniform constant (Case 2), on the gas–liquid transport and performance of PEMFCs; the novelty lies in the porosity gradient being along the channel direction, and the physical properties of the GDL related to porosity were modified accordingly. The results showed that at a high current density (2400 mA·cm−2), the GDL of Case 1 had a gas velocity of up to 0.5 cm·s−1 along the channel direction. The liquid water in the membrane electrode assembly could be easily removed because of the larger gas velocity and capillary pressure, resulting in a higher oxygen concentration in the GDL and the catalyst layer. Therefore, the cell performance increased. The voltage in Case 1 increased by 8% and 71% compared to Cases 2 and 3, respectively. In addition, this could ameliorate the distribution uniformity of the dissolved water and the current density in the membrane along the channel direction, which was beneficial for the durability of the PEMFC. The distribution of the GDL porosity at lower current densities had a less significant effect on the cell performance. The findings of this study may provide significant guidance for the design and optimization of the GDL in PEMFCs.

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“…[ 20–28 ] The problem of providing effective proton transport is particularly crucial in ionomer‐free catalyst film electrodes, where strategies developed to augment proton conduction can result in compromises between proton and oxygen transport, limiting electrode performance. [ 21,27,29–33 ]…”

Section: Introductionmentioning

confidence: 99%

Coaxial Nanowire Electrodes Enable Exceptional Fuel Cell Durability

et al. 2023

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Polymer‐electrolyte‐membrane fuel cells (PEMFCs) hold great promise for applications in clean energy conversion, but cost and durability continue to limit commercialization. This work presents a new class of catalyst/electrode architecture that does not rely on Pt particles or carbon supports, eliminating the primary degradation mechanisms in conventional electrodes, and thereby enabling transformative durability improvements. The coaxial nanowire electrode (CANE) architecture consists of an array of vertically aligned nanowires, each comprising an ionomer core encapsulated by a nanoscale Pt film. This unique design eliminates the triple‐phase boundary and replaces it with two double‐phase boundaries, increasing Pt utilization. It also eliminates the need for carbon support and ionomer binder, enabling improved durability and faster mass transport. Fuel cell membrane electrode assemblies based on CANEs demonstrate extraordinary durability in accelerated stress tests (ASTs), with only 2% and 5% loss in performance after 5000 support AST cycles and 30000 catalysts AST cycles, respectively. The high power density and extremely high durability provided by CANEs can enable a paradigm shift from random electrodes based on unstable platinum nanoparticles dispersed on carbon to ordered electrodes based on durable Pt nanofilms, facilitating rapid deployment of fuel cells in transportation and other clean energy applications.

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Ionic Conductivity over Metal/Water Interfaces in Ionomer‐Free Fuel Cell Electrodes

Cited by 15 publications

References 42 publications

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

Effects of Cathode GDL Gradient Porosity Distribution along the Flow Channel Direction on Gas–Liquid Transport and Performance of PEMFC

Coaxial Nanowire Electrodes Enable Exceptional Fuel Cell Durability

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