Exchange Membrane Fuel Cell Catalyst Research Articles

Preliminary Electrochemical Analysis of Carbon Nanoparticles from Candle Soot

Nanoparticles (NPs) generated by candle soot are of interest due to their potential applications. Because of their electronic properties, carbon-based zero-dimensional, one-dimensional, and two-dimensional nanomaterials such as graphene, fullerene, carbon nanotubes, and carbon nanofibers are extensively studied (1).However, synthesis of these nanomaterials is complex and expensive. Candle soot also contains fluorescent carbon NPswhich can be used for the preparation of fluorescent makers (2). The potential applications of candle soot NPs include energy storage [e.g., can be used for supercapacitor electrode material (3)], and conversion [fuel cells (4)]. Candle soot can be an excellent source of carbon NPs. In this presentation, we cover some challenges associated with carbon NPs, such as (a) instability of NPs due to agglomeration with time and increase in temperature and (b) separation and isolation of NPs. Thus, we focus on stabilization of NPs, isolation and characterization of NPs and to study electronic, optical, and electrochemical properties to determine whether they are promising candidate in the field of energy conversion.Candle soot formation depends on various parameters like substrate material, deposition time, flame temperature, wick dimension, and flame height (5). We developed a protocol for the collection of candle soot. With this proposed protocol, the carbon NPs generated from candle soot ranges from 50 nm to larger particle size which is confirmed by dynamic light scattering (DLS) technique shown in Fig. 1, and transmission electron microscope (TEM). We will include the electrochemical analysis such as investigation of oxidation/reduction processes to determine fundamental thermodynamic parameters of standard potential in organic solvents and aqueous solutions. References Jariwala, V.K. Sangwan, L.J. Lauhan, T.J. Marks, M.C. Harsam, Carbon nanomaterials for electronics, optoelectronics, photovoltaics, and sensing, Chem. Soc. Rev., 43 (2013), 2824-28.J. Campbell, M.J. Andrews, K.J. Stevenson, New nanotech from an ancient material: Chemistry demonstrations involving carbon-based soot, J. Chem. Educ., 89 (2012) 1280-1287.Zhang, D. Wang, B. Yu, F. Zhou, W. Liu, Candle soot as a supercapacitor electrode material, RSC. Adv., 4 (2014), 2586-2589.Khalakhan, R. Fiala, J. Laukova, P. Kus, A. Ostroverkh, M. Vaclavu, M. Vorokhta, I. Matolinova, V. Matolin., Candle Soot as an efficient support for proton exchange membrane fuel cell catalyst, Fuel Cell., 16 (2016) 652-655.N. Sahoo, B. kandasubramanian. An experimental design for the investigation of water repellent property of candle soot particles, Mater. Chem. Phys.,148 (2014), 134-142. Figure 1

Electrochemical Performances of PtCrCo Alloy/Nitrogen-Doped Activated Carbon for Proton Exchange Membrane Fuel Cell Catalyst

Proton Exchange Membrane Fuel Cell is a promising green energy conversion machine. However, some drawbacks, such as Pt corrosion on the cathode side, the high price of Pt, Nafion membrane, and the need for the high precision assembly process, limit their commercialization. In this study, PtCrCo alloy which is supported by nitrogen-doped activated carbon was synthesized by facile method to increase electrochemical performance as a cathode catalyst and reduce Pt catalyst usage. Nitrogen-doped Activated Carbon/PtCrCo/Nitrogen-doped Carbon (NAC/PtCrCo/N) catalyst was investigated to analyze the effect of increasing the composition of nitrogen-doped activated carbon in the synthesis process on the morphology and electrochemical performances of the catalyst. Polyaniline (PANI) as Nitrogen precursor was added to Activated Carbon (AC) powder with ratio of AC to PANI; 1:0, 3:1, 1:1, 1:3, as called AC, NAC1, NAC2, and NAC3 respectively. The catalyst synthesis process is carried out with the four activated carbon supports. Material characterizations were carried out using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller (BET), Cyclic Voltametry (CV), and Linear Sweep Voltametry (LSV). The XRD measurement shows that the addition of nitrogen doping tends to reduce the diffraction peak intensity of nitrogen-doped activated carbon compared to the pristine carbon. The doping also increases the surface area of the activated carbon as measured by the BET method. Nitrogen doping increases the conductivity and the addition of alloys can add better stability and catalytic activity for cyclic voltammetry results of the four catalysts cannot be calculated. The NAC3/Pt-Cr-Co/N electrocatalyst exhibited the highest initial potential at ~1 mAcm-2 of 0.997 V compared to the other four samples. On the other hand, AC/Pt-Cr-Co/N catalyst has the highest current density value of 22.156 mAcm-2.

(Digital Presentation) Synthesis of Proton Exchange Membrane Fuel Cell Catalyst and Optimization of Membrane Electrode Assembly Preparation Parameters

Reducing platinum content in proton exchange membrane fuel cells (PEMFCs) is one of the most essential development directions to secure the economic viability of PEMFC. Efforts are being made to synthesise new, more active catalysts and to optimise PEMFC assembly parameters. (1–4)The study aimed to synthesise 60 wt% Pt/C catalyst and optimise catalyst loading on the electrodes, gasket thickness and coating strategy.The catalyst was synthesised by depositing Pt nanoparticles on carbon black (Ketjenblack EC-300J) using ethylene glycol as a reducing agent and solvent (5–7). The studied catalyst was characterised by thermogravimetric analysis, X-ray diffraction and N2 sorption analysis. The synthesized catalyst material contained approximately 60 wt% of Pt, and the average platinum crystallite size was under 3 nm. The catalyst had a micro-mesoporous structure with a specific surface area of 320 m2 g−1.For electrochemical characterisation, the measurements were performed in H2/air PEMFC. Using an ultrasonic coating system, the catalyst was deposited on the Nafion membrane or gas diffusion layer. A suitable gasket thickness was found using electrochemical measurements. The catalyst loading was varied on the anode between 0.05 and 0.50 mg cm−2 and on the cathode between 0.40 and 1.00 mg cm−2, leaving the catalyst loading constant on the non-variable electrode. Electrodes thickness depended linearly on the catalyst loading. The results showed that electrochemically active surface area does not depend on catalyst loading. Varying catalyst loading on the anode did not show a decrease in electrochemical activity; thus, the anode catalyst loading could be reduced to 0.05 mg cm−2. However, the electrochemical activity decreased at low cathode catalyst loadings. It was found that the cathode catalyst loading can be reduced to 0.60 mg cm−2.Under optimised conditions, the electrochemical activity of the investigated material was excellent. The PEMFC current density was 0.81 A cm−2 at 670 mV, the maximum achieved power density 0.80 W cm−2 and the electrochemically active surface area 56 mPt 2 gPt −1. Acknowledgements This work was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011) and the Estonian Research Agency project (personal research support group grant project No. PRG676). References R. Alink, R. Singh, P. Schneider, K. Christmann, J. Schall, R. Keding, and N. Zamel, Molecules, 25, E1523 (2020).Á. Kriston, T. Xie, D. Gamliel, P. Ganesan, and B. N. Popov, Journal of Power Sources, 243, 958 (2013).J. Lee, C. Seol, J. Kim, S. Jang, and S. M. Kim, Energy Technol., 9, 2100113 (2021).H. A. Gasteiger, J. E. Panels, and S. G. Yan, Journal of Power Sources, 127, 162 (2004).Y. Shao, S. Zhang, R. Kou, X. Wang, C. Wang, S. Dai, V. Viswanathan, J. Liu, Y. Wang, and Y. Lin, Journal of Power Sources, 195, 1805 (2010).W. Li, C. Liang, W. Zhou, J. Qiu, Zhou, G. Sun, and Q. Xin, J. Phys. Chem. B, 107, 6292 (2003).R. Kou, Y. Shao, D. Mei, Z. Nie, D. Wang, C. Wang, V. V. Viswanathan, S. Park, I. A. Aksay, Y. Lin, Y. Wang, and J. Liu, J. Am. Chem. Soc., 133, 2541 (2011).

(Digital Presentation) Synthesis of Proton Exchange Membrane Fuel Cell Catalyst and Optimization of Membrane Electrode Assembly Preparation Parameters

The oxygen reduction catalyst was synthesized by depositing Pt nanoparticles on carbon black using ethylene glycol as a reducing agent. The synthesized catalyst material contained approximately 60 wt% of Pt, and the average Pt crystallite size was under 3 nm. The catalyst had a micro-mesoporous structure with a specific surface area of 320 m2 g−1. Electrochemical characterization was performed in H2/air fuel cell. The catalyst was deposited on the Nafion membrane or gas diffusion layer using an ultrasonic coating system. The thickness of Teflon gaskets as well as hot pressing conditions were optimized. Lowering catalyst loading on the anode did not show a decrease in electrochemical activity up to 0.05 mg cm−2. However, it was found that the cathode catalyst loading can be reduced only up to 0.60 mg cm−2.

Quantification and evolution on degradation mechanisms of proton exchange membrane fuel cell catalyst layer under dynamic testing conditions

The catalyst layer is one of the core components of the Proton Exchange Membrane Fuel Cell (PEMFC). Studying its degradation mechanism is very important to improve the durability of PEMFC. Therefore, the degradation of the catalyst layer after the 100 h, 225 h, and 650 h durability tests are studied quantitatively in this paper. The results show that the agglomeration of Pt particles is the main reason for the degradation of the catalyst layer in the first 100 h, accounting for 80%. Catalyst dissolution and the loss of proton connectivity caused by the ionomer are the main factors for the degradation of the catalyst layer between 225 and 650 h, which increases from 23% in the initial stage to 46%. In addition, the corrosion degree of the carbon support inside the catalyst layer gradually intensified with the test time. This study reveals the dominant degradation mechanism of the catalyst layer in different degradation stages and the evolution of the whole degradation process, which has important guiding significance for the structural design of the catalyst layer for long-life fuel cells.

Effect of micro-cracks on the in-plane electronic conductivity of proton exchange membrane fuel cell catalyst layers based on lattice Boltzmann method

Micro-cracks commonly occur on the catalyst layers (CLs) during the manufacturing of catalyst coated membranes (CCMs). However, the crack shape parameters effect on CLs in-plane (IP) electronic conductivity λs is not clear. In this work, the relationship between crack parameters and the λs is obtained based on the two-dimensional (2D) multiple-relaxation time (MRT) lattice Boltzmann method (LBM). The LBM numerical model is validated by the normalized λs experiment applied on three different home-made cracked CLs, and the parameter study focus on crack width, length, quantity and phase angle are carried out. The results show that the decrease of λs has different sensitivity |k| to the parameters above. The crack width has little effect on λs decrease, and the |kw| is 0.038. However, crack arm length and quantity show more significant impact, which |kl| and |kN| are 0.753 and 0.725, respectively. The CLs with different crack propagation directions show significant anisotropy on λs, and a 53.53% decrease in λs is observed between 0° and 90° crack phase angle change. To manufacture a high electronic conductivity CL, crack initiation and migration mitigation are highly encouraged.

Graphene-Derived Carbon Support Boosts Proton Exchange Membrane Fuel Cell Catalyst Stability.

The lack of efficient and durable proton exchange membrane fuel cell electrocatalysts for the oxygen reduction reaction is still restraining the present hydrogen technology. Graphene-based carbon materials have emerged as a potential solution to replace the existing carbon black (CB) supports; however, their potential was never fully exploited as a commercial solution because of their more demanding properties. Here, a unique and industrially scalable synthesis of platinum-based electrocatalysts on graphene derivative (GD) supports is presented. With an innovative approach, highly homogeneous as well as high metal loaded platinum-alloy (up to 60 wt %) intermetallic catalysts on GDs are achieved. Accelerated degradation tests show enhanced durability when compared to the CB-supported analogues including the commercial benchmark. Additionally, in combination with X-ray photoelectron spectroscopy Auger characterization and Raman spectroscopy, a clear connection between the sp2 content and structural defects in carbon materials with the catalyst durability is observed. Advanced gas diffusion electrode results show that the GD-supported catalysts exhibit excellent mass activities and possess the properties necessary to reach high currents if utilized correctly. We show record-high peak power densities in comparison to the prior best literature on platinum-based GD-supported materials which is promising information for future application.

Ionomer Distribution Strategy of Anion Exchange Membrane Fuel Cell Catalyst Layer in Terms of Interaction between Catalyst Slurry Components

Anion exchange membrane fuel cells (AEMFCs) have been intensively studied in recent years to replace proton exchange membrane fuel cells (PEMFCs). The acid-to-alkali transitions have the potential to lower overall system costs because it allows the non-precious metal catalysts and inexpensive metal stack hardware. Significant strides have been made in materials science in the last few decades, particularly the development of high IEC-containing anion exchange membrane (AEM) and ionomer (AEI) possessing high OH- conductivity, enabling comparable cell performance to that of PEMFC. In addition, the discovery of high HOR activity of PtRu by oxophilic and/or electronic effects, and reducing ionomer poisoning, provided an opportunity to further advance the cell performance of AEMFC. However, despite the remarkable development of materials, modest AEMFCs still have inadequate power performance (< 0.5 W cm-2) even using the precious catalysts, which stems from a lack of understanding of the catalyst layer (CL) design.CL consists of a catalyst and an ionomer, where the chemical energy of the fuel is converted into electrical energy in triple-phase-boundaries (TPBs). TPB is an electrochemically active site where catalyst (electrons), ionomer (H+ or OH-), and reactant gases were concurrent. In order to realize a high-performance fuel cell, the TPB should be high enough to utilize the capabilities of the catalyst, and the ideal state would be to maximize the contact area between the ionomer and the catalyst while minimizing the loss of CL porosity. Accordingly, the structure of the CL is one of the key factors that directly affect the performance of the fuel cell and is in great account.CL is fabricated from a slurry containing a catalyst, ionomer, and dispersing solvent, whose structure is determined by the complex interactions between slurry components. Therefore, fine-tuning of comprehensive interaction (catalyst/ionomer, catalyst/solvent, and ionomer/solvent) is the core technology in CL design, and an in-depth understanding of each interaction is also essential. In this regard, we recently presented the rational design of the CL by controlling AEI size, distribution via a solvent selection of the catalyst slurry. Specifically, the larger the solubility parameter (excluding the hydrogen bonding term) of the organic solvent mixed with water, the smaller the dispersed AEI size, leading to an even distribution of the AEI in the CL. This induces a high electrochemical surface area of the CL, making it possible to achieve high performance AEMFC from the low current region. However, nevertheless, we found that the distribution of AEI in the AEMFC catalyst layer was still not completely uniform through various types of electron microscopy analysis. In particular, when the morphology of the AEMFC CL was compared with the Nafion ionomer (commonly used in PEMFC field) as a reference, AEI caused lower porosity by clogging the pores of Pt/C nanoparticles. For this reason, we found that AEMFCs had lower performance than Nafion-based PEMFCs, despite their high ORR activity under alkaline conditions.Molecular dynamics (MD) and density functional theory (DFT) simulation analyzes show that AEI has a particularly low interaction with carbon compared to Nafion, and for this reason, we found that AEI aggregates with each other rather than evenly distributed on the Pt/C surface. We used QPC-TMA as AEI in this study and confirmed that commercialized AEI (FAA-3 and XA-9) also form low CL porosity and pore-closing characteristics. This result suggests that low interaction between AEI/carbon is a universal property of current levels of AEI. Therefore, when designing an ionomer to improve the performance of AEMFC, high interaction with carbon should be considered as another important variable.

Magnéli TiO2 as a High Durability Support for the Proton Exchange Membrane (PEM) Fuel Cell Catalysts

Proton exchange membrane fuel cells (PEMFCs) cathode catalysts’ robustness is one of the primary factors determining its long-term performance and durability. This work presented a new class of corrosion-resistant catalyst, Magnél TiO2 supported Pt (Pt/Ti9O17) composite, synthesized. The durability of a Pt/Ti9O17 cathode under the PEMFC operating protocol was evaluated and compared with the state-of-the-art Pt/C catalyst. Like Pt/C, Pt/Ti9O17 exhibited exclusively 4e− oxygen reduction reaction (ORR) in the acidic solution. The accelerated stress tests (AST) were performed using Pt/Ti9O17 and Pt/C catalysts in an O2-saturated 0.5 M H2SO4 solution using the potential-steps cycling experiments from 0.95 V to 0.6 V for 12,000 cycles. The results indicated that the electrochemical surface area (ECSA) of the Pt/Ti9O17 is significantly more stable than that of the state-of-the-art Pt/C, and the ECSA loss after 12,000 potential cycles is only 10 ± 2% for Pt/Ti9O17 composite versus 50 ± 5% for Pt/C. Furthermore, the current density and onset potential at the ORR polarization curve at Pt/C were significantly affected by the AST test. In contrast, the same remained almost constant at the modified electrode, Pt/Ti9O17. This demonstrated the excellent stability of Pt nanoparticles supported on Ti9O17.

Nonconformal Particles of Hyperbranched Sulfonated Phenylated Poly(phenylene) Ionomers as Proton-Conducting Pathways in Proton Exchange Membrane Fuel Cell Catalyst Layers

Characteristic poor electrochemical kinetics, high ionic resistance, and high mass transport resistance within the catalyst layer (CL) are chief among parameters that cause poor performance of proton exchange membrane fuel cells (PEMFCs) utilizing hydrocarbon-based proton-conducting ionomers. Herein, the design and addition of nondimensionally swellable, nonconformal, hyperbranched sulfo-phenylated poly(phenylene) ionomer particles (HB-sPPT-H+) are reported to introduce a direct pathway for proton conduction in hydrocarbon ionomer-based CLs, resulting in an eight times reduction in ionic resistance of the CL, a 71% increase in catalyst mass activity, and a >90% increase in power at 0.6 V (H2/air) compared to state-of-the-art hydrocarbon ionomer-based CLs. The benefits of incorporating HB-sPPT-H+ ionomer particles are also shown when employed in perfluorosulfonic acid (PFSA) ionomer-based PEMFCs. These results dispel a commonly held conception that hydrocarbon ionomers possess limitations of gas permeability and electrochemical activity and open up previously unexplored avenues of ionomer development for nonfluorous, wholly hydrocarbon PEMFCs.

Electrospray Deposition: A Breakthrough Technique for Proton Exchange Membrane Fuel Cell Catalyst Layer Fabrication

This Spotlight article presents the state-of-the-art of electrospray deposition technique applied to the fabrication of proton exchange membrane fuel cell (PEMFC) components, mainly focusing on catalyst layers in gas diffusion electrodes. The atomization of a suspension of particles over a substrate under the influence of a strong electric field results in the growth of a film with macroporous morphology and many interesting properties. This so-called electrospray deposition has reported many noteworthy beneficial effects for the fabrication of the catalyst layers of gas diffusion electrodes of PEMFCs. The electrosprayed catalyst layers prepared from suspensions of catalyst particles and ionomers present a dendritic macroporous morphology with superhydrophobic character that improves the water management inside the cell and increases the performance by ∼20% with respect to standard electrodes prepared by airbrushing. Other interesting effects observed with electrosprayed catalyst layers are increased catalyst utilization and water absorption capabilities of the ionomer, improved performance under nonhumidified conditions, and a reduction in catalyst degradation. In addition, the electrospray deposition decreases platinum losses during fabrication thanks to the attractive electrostatic forces between the ion mist and the substrate compared with regular ink-based spray methods.

Platinum supported on pristine and nitrogen-doped bowl-like broken hollow carbon spheres as oxygen reduction reaction catalysts

The development of active and durable proton exchange membrane fuel cell catalysts with high loading (ca. 40%) is critical for the commercialization of hydrogen fuel cells. Herein we report on the synthesis of a novel Pt/C catalyst using a novel bowl-like broken hollow carbon sphere (and N-doped sphere) support (carbon shell thickness ~ 4.6 nm). Highly dispersed Pt nanoparticles (dPt ~ 4 nm) were deposited on both supports and within the carbon shell. The Pt particles in the pores were exposed on both sides of the shell, while the shell porosity ensured pore confinement of the Pt. Both catalysts exhibited high electrochemical surface areas (60–65 m2 g−1) and cycling durability (6000 cycles) that was superior to a commercial benchmark Pt/C catalyst. These studies indicate that high loadings of confined small Pt particles on both sides of thin interconnected carbons can lead to high oxygen reduction reaction activities and durability.Graphic abstract

Effects of ionomer and dispersion methods on rheological behavior of proton exchange membrane fuel cell catalyst layer ink

The catalyst layers of proton exchange membrane fuel cells are usually fabricated by (1) mixing catalyzed carbon black, ionomer solution, and solvents to form an ink, (2) coating this ink by spraying or transferring from decal to a membrane or gas diffusion layer, and (3) drying. During the mixing stage, dispersion methods, such as ball milling and sonication, are employed to homogenize the ink and prevent agglomeration of solid ingredients. The present study focused on the first step of fabricating the catalyst layer and conducting a rheological investigation on catalyst inks. The viscosity and thixotropy of inks that were prepared by ball milling and sonication, respectively, were measured, and some major factors affecting the change in the viscosity were analyzed. The catalyst layer inks exhibited pseudoplastic fluid behavior, which was clearly non-Newtonian, and their viscosity decreased with stress rate. The results indicated that the ionomer solution plays a decisive role in the dispersion of carbon-supported catalysts. Hence, homogeneous ink cannot be formed without the ionomer solution. The viscosity of the ink was dependent on the solid content ratio and the dispersion method used, while the dispersion time and amplitude were less critical. Ball milling and sonication methods result in inks with different rheological characteristics. Rheological data indicate that the thixotropic recovery of the ink prepared by ball milling is faster in comparison to that prepared by sonication.

A practical method to characterize proton exchange membrane fuel cell catalyst layer topography: Application to two coating techniques and two carbon supports

The coating technique and the type of carbon support can strongly affect the surface topography, the homogeneity and the thickness of the catalyst layers of Proton Exchange Membrane fuel cells. These features can in turn strongly modify the local diffusion properties of the layer and the final cell performance, but literature about catalytic layers does not often address such issues. This work aims at studying the topography of proton exchange membrane fuel cell catalyst layers by means of 3D characterization methods. For that purpose, two types of slurries, made of NafionⓇ and carbon black or a carbon xerogel, have been coated on a KaptonⓇ sheet by film-casting and by spray-coating. The surface topography of the samples was characterized by contact profilometry and 3D laser scanning microscopy. The data obtained with both methods were processed in order to obtain accurate 3D representations of the surface of the layers. Contact profilometry allows to perform measurements over the entire surface of the sample (5 cm × 5 cm). Layers obtained by film-casting turn out to be very smooth, but also thinner at the edges of the coating. For layers prepared by spray-coating, the reproducibility and the homogeneity are improved; however, the surface displays a higher roughness. With 3D laser scanning microscopy measurements, only a small part of the sample was analyzed (0.25 cm2) with a high definition, allowing to characterize more precisely the surface topography. The comparison of both techniques has been enriched by the simulation of the profilometer tip motion at the surface of the observed 3D microscopy profile, giving insight into the observed differences. The 3D microscopy measurements proved to be more accurate, but not representative of the whole sample, especially for less homogeneous layers prepared by film-casting.

Pore-scale study of pore-ionomer interfacial reactive transport processes in proton exchange membrane fuel cell catalyst layer

Abstract Understanding interactions between constituent distributions and reactive transport processes in catalyst layer (CL) of proton exchange membrane fuel cell is crucial for improving cell performance and reducing cell cost. In this study, high-resolution porous structures of cathode CL are reconstructed, where all the constituents in CLs are resolved. A pore-scale model based on the lattice Boltzmann method is developed for oxygen diffusion in pores and ionomer, as well as electrochemical reaction at the Pt surfaces. Particularly the model considers the pore-ionomer interfacial transport processes with distinct characteristics of sharp concentration drop, large diffusivity ratio and interfacial dissolution reaction. After validated by interfacial transport processes with analytical solutions, the pore-scale model is applied to reactive transport processes inside complex CL nanoscale structures. Pore-scale results reveal that pore-ionomer interfacial transport processes generate extremely high local transport resistance, significantly reducing the total reaction rate. As volume fraction of carbon increases, the value of the optimum ionomer content generating the best cell performance decreases, while the value of the optimum ionomer content resulting in the lowest performance loss under low Pt loading reduces. The two values generally are different. The pore-scale model helps to understand reactive transport processes and to optimize the CL structures.

Influence of dispersion media on Nafion® ionomer distribution in proton exchange membrane fuel cell catalyst carbon support

Abstract Interface between the Nafion® ionomer on the high surface area carbon used as catalyst support in the polymer electrolyte membrane fuel cell (PEMFC) electrodes has been studied through a combination of microscopic, spectroscopic and electrochemical techniques. Different support/ionomer interface structures have been developed by varying the dispersion media for ink preparation while keeping the solid composition of the ink invariant. Structural characterizations such as elemental mapping, thermogravimetric analysis and Raman/Infrared spectroscopy of the dried inks reveal significant impact of the dispersion media on the distributions of the ionomer/support phases. Further, variation of the double layer capacitance (DLC) of the ionomer/support inks coated on gold electrodes with the scan rate during cyclic voltammetry measurements has been studied to evaluate the ionomer/support interface performance. Substantial impact of the dispersion media has been observed on the scan rate/DLC profiles for the inks. Low ratios of the DLC values at scan rates of 1000 and 100 mV/s have been observed for the ionomer/carbon support inks having partially inhomogeneous ionomer/carbon distribution. Finally, infrared spectroscopy suggested different interactions of the –SO3 group with the support carbon for the inks prepared using different types of dispersion media.

Liquid Water Uptake and Contact Angle Measurement of Proton Exchange Membrane Fuel Cell (PEMFC) Electrodes

In this work, capillary rise experiments were performed to assess the wetting properties of free-standing proton exchange membrane fuel cell catalyst layers (CLs) with several ionomer chemistries (equivalent weight -EW- ranging from 540 to 1115). The samples were attached to a micro-balance and then immersed into liquid water to (i) measure the mass gain from the liquid uptake and (ii) estimate the (external) contact angle to water. The results showed that the ionomer EW had an impact on the CL wettability. Specifically, a highly hydrophobic behavior was observed at high ionomer EW (i.e., 1115): 173° contact angle to water. More hydrophilic behavior was observed at low ionomer EW (i.e., 540): 107° contact angle to water. For an intermediate range of ionomer EW (i.e., from 620 to 1100), minimal variation in the CLs wetting properties was observed at an average contact angle of 160°.

PEDOT/C Composites used as a Proton Exchange Membrane Fuel Cell Catalyst Support: Role of Carbon Amount

AbstractCarbon‐based support materials are mostly used in proton exchange membrane fuel cells (PEMFCs); however, they often suffer from degradation under the operating conditions. In this context, conducting polymers and their composites stand out as a good alternative support material thanks to their chemical stability, high electrical conductivity, and higher oxidation‐resistant properties, which fulfills the requirements for possible utilization as electrocatalyst in PEMFCs. This study reports the preparation of poly(3,4‐ethylenedioxythiophene)/carbon (PEDOT/C) composite‐supported Pt nanoparticles for PEMFC electrodes. First, PEDOT/C composites were prepared using different carbon amounts by in situ chemical oxidative polymerization of EDOT monomer on carbon particles. Then, Pt nanoparticles (about 20 % loading) were obtained by using a microwave irradiation technique as it is fast, inexpensive, energy and time saving, and ecofriendly. The successful synthesis was confirmed by XRD, TEM, and thermogravimetric analysis investigations. The surface area and pore structure of the PEDOT/C supports was also investigated by using the BET technique. The ex situ and in situ electrochemical analyses were performed by using cyclic voltammetry and PEMFC performance tests. The obtained results for the fuel cell open the way for the use of PEDOT/C composite support materials as electrocatalysts for fuel cells.

A multiscale approach to accelerate pore-scale simulation of porous electrodes

Abstract A new method to accelerate pore-scale simulation of porous electrodes is presented. The method combines the macroscopic approach with pore-scale simulation by decomposing a physical quantity into macroscopic and local variations. The multiscale method is applied to the potential equation in pore-scale simulation of a Proton Exchange Membrane Fuel Cell (PEMFC) catalyst layer, and validated with the conventional approach for pore-scale simulation. Results show that the multiscale scheme substantially reduces the computational cost without sacrificing accuracy.

Candle Soot as Efficient Support for Proton Exchange Membrane Fuel Cell Catalyst

AbstractCandle soot deposited from the candle flame was used as a catalyst support for an anode catalyst in a proton exchange membrane fuel cell. The results showed that Pt/soot hybrids prepared by magnetron sputtering of 5 nm platinum films on candle soot exhibit very high mass activity in the fuel cell, which is more than one order of magnitude higher than that for commercial catalyst. The elementary preparation, high surface‐to‐volume ratio, good conductivity and hydrophobicity make candle soot a promising type of the support for PEMFCs catalyst.