bluuebunny/crossref_metadata_2025_split huggingface dataset:
Towards Improved Cold-Start Capability of PEFCs: Patterned Gas Diffusion Layers
Authors: Liu Wenmei , Lee Jongmin , Schmidt Thomas J. , Boillat Pierre 
Published: September 2023

Polymer electrolyte fuel cells (PEFCs) are electrochemical energy converters with high efficiency and zero pollutant emissions. The unassisted cold-start of PEFCs at -30 °C is one of the major challenges for automotive applications due to the freezing of supercooled water generated by the cathodic oxygen reduction reaction (ORR). Once triggered by the nucleus in cathode gas diffusion layers (GDLs), ice propagates through the active area, leading to oxidant gas blockage and cold-start failure1.
The cold-start capability of PEFCs can be improved by preventing ice propagation, especially in GDLs. In our previous work2,3, after the GDLs were segmented by polytetrafluoroethylene (PTFE) into two regions, the PEFC kept operating for another 30 minutes after the first freezing event in one region. Nevertheless, the PTFE barrier limited the active area as well as the heat and electric conductivity of PEFCs. In contrast, patterned GDLs allow water cluster separation without the abovementioned limitations. The improvement of water management and cell performance under technical operating conditions was demonstrated4. Yet, the cold-start capability with patterned GDL needs to be further investigated.
This work studies the effect of patterned GDLs on the water-ice phase transition and cold-start capability of PEFCs. First, non-isothermal differential scanning calorimetry (DSC) measurements were conducted to determine the onset freezing temperature distribution of supercooled water in patterned GDLs, taking into account various properties such as coating load and pattern size. It was observed that independent freezing events occurred in patterned GDLs in all cycles, as several freezing/exothermic peaks can be seen in Figure
1b. In contrast, ice propagated immediately in untreated GDL, as only one freezing peak was observed in all cycles (Figure 1d). By computing the integral of the heat flux curve, we obtained the corresponding cumulative icing ratio over 60 cycles, as presented in Figures 1a and 1c. The effective prevention of ice propagation is only observed in patterned GDLs. Second, to assess the cold-start capability, statistical isothermal cold-start measurements were conducted using a 4.4 cm2 differential cell, with the cell temperature held at -7.5 °C, -10 °C, -15 °C, and 20 °C. In summary, nonconcurrent freezing events in patterned GDLs indicate that the use of patterned GDLs significantly improved the cold-start capability of PEFCs under isothermal subfreezing conditions.
The findings of this work enhance the understanding of the cold-start dependence on the GDL and contribute to the development of unassisted freeze-start technology for PEFCs and the expansion of PEFCs applications.

Figure 1
Evaluation of Phosphoric Acid Leaching in PBI Membranes for High-Temperature PEM Fuel Cells By Ex-Situ and Operando Characterization Methods
Authors: Chen Jianuo , Perez-Page Maria , Holmes Stuart 
Published: September 2023

High-Temperature PEM Fuel Cells (HT-PEMFCs) based on PA-doped-PBI membranes have become a promising sustainable power generation system due to their high proton conductivity, high tolerance to hydrogen impurities, thermal stability and high utilization of waste heat [1]. Unlike low-temperature fuel cells based on perfluorosulfonic acid polymers (Nafion), HT-PEMFCs do not need water to act as a proton conductor, instead a hydrogen-bonded matrix is established between PA and PBI, negating the need for humidification in the system. As a result, the proton conductivity of the PA-doped PBI membrane is related to its PA loading. When PA is added to the PBI membrane, each PBI repeat unit can only bond with two PA molecules, leading to higher doping levels due to PA distributed in the PBI matrix in a free state. This extra PA leaches from the membrane to the electrodes during cell operation [2] resulting in several problems, the reduction of the proton conductivity of the membrane, blocking of the pathway for the gases to and from catalytically active sites and drive the migration of Pt-based catalyst, resulting in an increase in both mass and charge transfer resistances [3].
To prevent acid leaching out of the membrane and the subsequent negative effects on the fuel cell performance, Single Layer Graphene (SLG) has been incorporated as barrier material between the PEM and cathode/anode. SLG acts as sieve material to block all atoms and molecules from passing through with the exception of protons improving the performance and the long-term of the HT-PEMFC [4]. However, although the electrochemical characterization proves this enhancement, the mechanism of the phosphoric acid migration and the effect of the SLG on the leaching is still unknown.
In this work, different techniques, X-rat CT [4, 5]y, Raman microscopy [5] and µ-XRF, have been used to evaluate the PA leaching under ex-situ and in-operando conditions to study the mechanism of the migration of the acid and to prove that the electrochemical improvement is due to SLG has a positive effect in the HT-PEMFC.

References:

[1] Y.-L. Ma, et al., Journal of the Electrochemical Society 151(1) (2003) A8.
[2] S. Galbiati, et. al., International journal of hydrogen energy 38(15) (2013) 6469-6480.
[3] S.H. Eberhardt,et al., Journal of the Electrochemical Society 162(3) (2015) F310.
[4] Chen, J, et al. Nano Energy, 93 (2022) 106829
[5] Bailey, J, et al. Journal of Power Sources 509 (2021) 230347.

Figure 1
Boron-Activating Ruthenium from Organic-Free Synthesis Process: A Hydrogen Oxidation Reaction Catalyst for Anion Exchange Membrane Fuel Cells
Authors: Cui Yingdan , Wang Yian , Liu Guimei , Yang Fei , Zhu Shangqian , Wu Hsiwen , Mustain William Earl , Shao Minhua 
Published: September 2023

Using fossil fuels, power generation is always accompanied by environmental pollution. However, hydrogen-oxygen fuel cells, using H2 generated from renewable energy, can provide electricity with zero emissions, meeting the significant demands. Proton exchange membrane fuel cells (PEMFCs), though commercialized, are hindered by the high cost due to relying on expensive Pt. By contrast, as the potential alternative, anion exchange membrane fuel cells (AEMFCs), have attracted more and more attention as they can provide the benefit of using low-cost cathode catalysts while still having high power density. Although the oxygen reduction reaction (ORR) on the cathode can be well achieved by platinum group metal (PGM)-free catalysts in an alkaline environment, the high loading of Pt for the anode is still needed for high power output caused by the sluggish hydrogen oxidation reaction (HOR) kinetics. As the cheapest PGM, Ru with lower HOR activity is often added as an activity promoter to reduce the Pt loading. Recently, more efforts have been put into using exclusively Ru as the main catalysis active site, but the synthesis methods are often complex and involve toxic organics.
In this project, boron-activated Ru supported on carbon was developed for HOR catalysis in alkaline media. The B-Ru/C was synthesized by a simple organic-free method, making it possibly attractive for industrial application. This method adopted water as the only solvent and boric acid as the boron source to avoid the toxic problem and the tedious removal step of organics. It produced uniformly dispersed Ru nanoparticles in smaller particle sizes with a boron-rich environment verified by TEM and STEM images. Compared to Ru/C or Ru/BC, B-Ru/C not only has a higher electrochemical active surface area (ECSA) but also reached a much higher ECSA-normalized exchange current density which means boron does promote the activity of Ru. From the XPS spectra, the more significant peak shifts of Ru3p and B1s in B-Ru/C relative to Ru/C and BC indicate that the boron-ruthenium interaction is more robust in B-Ru/C than in Ru/BC. A theoretical simulation was conducted further to understand the mechanism of the HOR activity enhancement. From an electrochemical perspective, the B-Ru/C had a very high exchange current density in ex-situ tests and was also studied as an anode in operating AEMFCs. We believe this cost-effective Pt-free HOR catalyst with excellent performance prepared through an organic-free process can contribute to the industrial application of AEMFCs in the future.
Acknowledgments
This work is supported by the Research Grant Council (HKUST C6011-20G).
(Invited) Size, Composition Effects and Active State Formation of Nanostructured Cobalt and Iron-Cobalt Oxide-Based Catalysts during Oxygen Evolution Reaction
Authors: Roldan Cuenya Beatriz 
Published: September 2023

The efficient water electrolysis is a key technology to establish a CO2-neutral, electrochemical (green) hydrogen production. Nonetheless, the electrocatalysts’ near-surface structure during the anodic oxygen evolution reaction (OER) is still largely unknown, which hampers knowledge-driven optimization. Here, we provide quantitative near-surface structural insights into oxygen-evolving CoOX(OH)Y nanoparticles by tracking their size-dependent catalytic activity down to 1 nm and their structural adaptation to OER conditions combining operando X-ray absorption spectroscopy and density functional theory calculations. We uncover a superior intrinsic OER activity of sub-5 nm nanoparticles and a size-dependent oxidation leading to a near-surface Co-O bond contraction and charge redistribution during OER.
I will also report on the role of Fe in the performance of Co-oxide-based electrocalysts. By comparing epitaxial Co3O4(111), Co1+δFe2-δO4(111) (|δ|<=0.2), and Fe3O4(111) thin film electrocatalysts combining quasi in-situ preparation and characterization in ultra-high vacuum (UHV) with electrochemistry experiments. Interestingly, Co1+δFe2-δ O4(111) was found to be up to five times more active than Co3O4(111) and Fe3O4(111) with the activity depending acutely on the Co/Fe concentration ratio. Under OER conditions, all three oxides are covered by oxyhydroxide but the characteristics of this overlayer, including its thickness, stability, structural and chemical evolution was found to depend on the Fe content.
High-Throughput Activity Screening of Oxygen Reduction and Oxygen Evolution Catalysts
Authors: Park Jaehyung , Myers Deborah J. 
Published: September 2023

High-throughput techniques are being actively studied to expedite the evaluation of the electrocatalytic activity of newly developed materials. These techniques include the use of optical sensing or electrochemical array cells in stagnant or hydrodynamic aqueous electrolytes [1-2]. A new high-throughput electrochemical cell has been developed utilizing multiple glassy carbon working electrodes with dimensions comparable to those of a conventional ring-disk electrode (RDE) that are inserted into a channel flow cell (Figure 1) comprised of two PEEK blocks separated by a gasket that defines the electrolyte channel depth. This cell enables evaluation of the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) activity as a function of the potential of multiple catalyst samples simultaneously that are deposited on the glassy carbon electrodes using standard methods used for RDE electrodes (e.g., using a hand-held micropipette). As shown in Figure 1, a common reference electrode is located in the lower cell block across an electrolyte channel from the working electrodes and a common counter electrode is located in the electrolyte outlet. Electrolyte flow has been simulated to ensure that the electrolyte is evenly distributed throughout the shallow flow channel with uniform laminar electrolyte flow and identical flow rate for all working electrodes. The new cell is coupled with a Bio-logic multichannel Potentiostat (VSP) that allows the use of multiple working electrodes simultaneously with a common counter electrode and common reference electrode. The catalyst activity and stability results obtained with the new cell have been verified by comparison with RDE measurements for the same catalysts.

Acknowledgments

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the Electrocatalysis Consortium (ElectroCat). Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.

References

[1] Gregoire, J.M., et al., Scanning droplet cell for high throughput electrochemical and photoelectrochemical measurements. Review of Scientific Instruments, 2013. 84(2).
[2] Reddington, E., et al., Combinatorial electrochemistry: A highly parallel, optical screening method for discovery of better electrocatalysts. Science, 1998. 280(5370): p. 1735-1737.

Figure 1
Hydrogen Reconversion from Ammonia through Anion Exchange Membrane Electrolysis
Authors: Kanaan Riham , Affonso Nóbrega Pedro Henrique , Beauger Christian 
Published: September 2023

Nitrogen-based compounds, especially ammonia, is a promising alternative for the storage and transport of renewable hydrogen over long distances [1]. Considering ammonia as a hydrogen carrier will require studying the conversion (ammonia to hydrogen) and reconversion steps (hydrogen to ammonia). The reconversion of ammonia can take place through electrolysis under alkaline conditions [2] and needs the development of more efficient catalysts. For this, we started studying the electro-oxidation of ammonia in an anion exchange membrane electrolyser over platinum-based and PGM free electrodes with KOH as electrolyte. We have prepared several catalysts, carbon supported platinum, platinum-iridium, and nickel nanoparticles using the polyol technique. Commercial carbon supported platinum nanoparticles was used as catalyst for the cathodes. Catalyst coated substrates (CCS) were then prepared by spraying a catalytic ink over stainless-steel fiber paper for the anode side. The formulation of the ink requires optimizing parameters such as the type of ionomer (nafion, sustanion) and the ratio of ionomer to carbon. Anodes obtained have been assembled with anion exchange membranes and commercial cathodes for ammonia electro-oxidation in single cell. We have compared the performance of these different membrane electrodes assemblies (MEAs) to commercially available ones integrating nickel-iron-cobalt based anodes. The performance of MEAs was analyzed based on polarization curves, cyclic voltammograms and impedance spectroscopy data. Different testing conditions were investigated by varying the ammonia concentration from 0.1 to 1 M, the temperature from 25 °C to 60°C, and the KOH concentration from 0.1 to 5 M.
References:
[1] N. Morlanés et al., “A technological roadmap to the ammonia energy economy: Current state and missing technologies,” Chem. Eng. J., vol. 408, 2021, doi: 10.1016/j.cej.2020.127310.
[2] N. M. Adli, H. Zhang, S. Mukherjee, and G. Wu, “Review—Ammonia Oxidation Electrocatalysis for Hydrogen Generation and Fuel Cells,” Journal of the Electrochemical Society, vol. 165, no. 15. pp. J3130–J3147, 2018, doi: 10.1149/2.0191815jes.
Valorization of Naturally Abundant Low-Value Peat into Highly Active Non-Platinum Group Metal Oxygen Reduction Catalysts
Authors: Teppor Patrick , Jäger Rutha , Nerut Jaak , Koppel Miriam , Aruväli Jaan , Volobujeva Olga , Lust Enn 
Published: September 2023

As society continues to adopt an increasingly eco-friendly stance, the efficient usage of natural resources needs to be maximised. For instance, energy obtained from biomass covers roughly a tenth of the global demand. This biomass can instead be used as a carbon source to produce value-added materials such as tnon-platinum group metal (NPGM) oxygen reduction catalysts, which are desperately sought after as global demand for fuel cells continues to rise [1,2]. For example, peat is an extremely abundant biomass material in Estonia covering roughly 20% of the country [3]. Herein, the viability of using peat-based catalysts as oxygen reduction catalysts in alkaline media was investigated.
The peat sourced from a local peatland was processed and modified with inexpensive iron and nitrogen precursors through the common double-pyrolysis and acid washing synthesis procedure into peat-based NPGM catalysts. Additionally, zinc chloride was used as a pore forming agent. The influence of several principal synthesis parameters, e.g. precursor compound type and amount, on the physical and electrochemical properties of these materials was investigated using various characterization methods.
The NPGM catalysts obtained from naturally abundant peat were highly microporous systems due to the inclusion of zinc chloride in the synthesis mixture. High onset (~0.93 V vs RHE) and half-wave potential (~0.83 V vs RHE) values were obtained for most of the materials in activity screening experiments conducted with a rotating disc electrode setup using 0.1 M KOH. However, using an excessive amount of the nitrogen precursor in the synthesis proved to be detrimental to the obtained activity. The high activity of the obtained peat-derived catalysts was further investigated in a rotating ring disc electrode setup where the influence of the studied synthesis parameters on the oxygen reduction reaction selectivity was more evident.

Acknowledgments

This work was supported by the EU through the European Regional Development Fund under projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR “Nanomaterials - research and applications” (3.2.0304.12-0397), NAMUR+ core facility funded by the Estonian Research Council (TT 13), PRG676 “Development of express analysis methods for micro-mesoporous materials for Estonian peat derived carbon supercapacitors” (01.01.2020–31.12.2024) and PUT1581 (1.01.2017–31.12.2020).

References

F. Jaouen, D. Jones, N. Coutard, V. Artero, P. Strasser, A. Kucernak, Johns. Matthey Technol Rev. 2018, 62, 231.

E4tech, 2022, The Fuel Cell Industry Review 2021.

M. Orru, H. Orru, Est. J. Earth Sci. 2008, 57, 87.
(Invited) Electrocatalytic Synthesis of Ammonia and Urea
Authors: Costa Figueiredo Marta 
Published: September 2023

Many industrial chemical processes involve a high-energy demand (often still derived from fossil fuels), toxic reactants, and the production of high amounts of waste. A good example is the production of ammonia and urea via the Haber-Bosh and Bosch-Meiser processes, respectively. These two nitrogen-containing compounds are mostly used in the fertilizer industry and with the increase in the world population, their production is expected to increase. Additionally, NH3 itself is responsible for 2% of the annual world energy consumption and has a carbon footprint of 1.5 tons of CO2 per ton of NH3 [1]. Therefore, the development of more efficient, less hazardous technologies that are based on renewable energies to produce valuable N- containing compounds, has become one of the most challenging topics for chemical synthesis. By using electrochemical methods for the synthesis of ammonia and urea, toxic and dangerous chemicals can be replaced with clean electrons. Furthermore, the efficiency and selectivity of the reactions can be tuned by the applied potential, and more importantly, the energy used can come from renewable sources like wind or solar [2].
In this talk, I will show the recent advances from our group in the development of catalysts for the electrocatalytic synthesis of ammonia and urea (as for example Cu2O and CuRh) and the reaction mechanism when using nitrate as a substrate [3].

References:

[1] S. Giddey, et al, Int. J. Hydrogen Energy, 38 (2013) 14576–14594
[2] Frontana-Uribe, B. A. et al; Green Chem. 2010, 12 (12) 2099– 2119
[3] D. Anastasiadou, Y. van Beek, M. C. Figueiredo, in preparation.
Selective Separation between Ammonium and Potassium in a Membrane-Separated Magnesium-Based Electrochemical Process
Authors: Akbari Amir , Logan Bruce E. , Greenlee Lauren F 
Published: September 2023

Increasing trends in global food and water demands alongside growing environmental concerns press the need for developing new wastewater management strategies. Modern wastewater treatment facilities should provide nutrient recovery and recycling, localized production capabilities, and low energy consumption. Magnesium-based electrochemical wastewater treatment processes are one technology option with the potential to address these needs by providing opportunities for simultaneous recovery of valuable resources from waste streams. In this system, phosphate and ammonium coprecipitate with the magnesium released from the sacrificial anode, producing struvite, NH4MgPO4, as a fertilizer. This technology also eliminates the disadvantages of the commonly used chemical precipitation method of struvite recovery, including magnesium salt dosing, and adding base to the system for pH control, due to in situ magnesium corrosion and hydroxide production at the magnesium anode surface.
In this presentation, we specifically focus on a membrane-separated electrochemical process with a solid magnesium electrode. A complex synthetic water matrix including key ions such as ammonium, potassium, and phosphorus with other background salts was made for the anodic chamber to simulate animal liquid manures. Sodium sulfate solution was used as the supporting electrolyte on the cathodic chamber. Two different cation exchange membranes (CEMs) were placed between the two compartments to separate the anolyte from the catholyte. All experiments were conducted under OCV (no external energy input), and ion concentrations in each chamber were tracked over time using ion chromatography to perform kinetic study. The produced precipitates from each experiment are collected and have been characterized by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX) to identify the morphology and purity of the produced solid precipitates. Furthermore, X-ray diffraction (XRD) and Fourier-transform infrared spectrometry (FT-IR) were used to exactly identify the nature of the precipitates. Experimental results indicate that magnesium electrode corrosion under OCV in the anolyte will decrease ammonium separation through the CEM to the catholyte compared to potassium.