bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium Borohydride Oxidation on Pt and/or Pd-Based Electrodes in Hydrogen Peroxide Direct Borohydride Fuel Cells (H2O2-DBFCs)
Authors: Hjelm Rachel Marielle Emily , Garsany Yannick , Atkinson Robert W. , Stroman Richard O'Neil , Swider-Lyons Karen , Lafforgue Clémence , Chatenet Marian 
Published: February 2020

Direct borohydride fuel cells (DBFCs) may offer high energy density due to the potential release of 8 electrons when borohydride (BH4
-) has been fully oxidized (overall reaction: BH4
- + 8OH- à BO2
- + 6H2O + 8e-). However, the borohydride oxidation reaction (BOR) is complex producing several reaction intermediates and solid borates1, and may compete with the heterogeneous hydrolysis of BH4
- to produce H2, which can be lost. In consequence, the full 8-electron oxidation reaction may be practically inaccessible. Incomplete BOR is largely due to transport of intermediate species away from the electrocatalyst before complete oxidation can occur. The escape of incompletely oxidized species leads to BH4
- and intermediate species concentrations (including H2) which vary as the fuel solution progresses through the fuel cell flow field 2. For this reason, the optimal catalyst layer composition and porosity are likely different at the fuel inlet vs outlet, making the catalyst layer and overall cell design a challenge.
In this study, the direct electrooxidation of sodium borohydride (NaBH4) is investigated within a liquid flow-through DBFC having a catalyst composition which varies from inlet to outlet. Electrochemical and spray coating deposition are used to form catalyst layers composed of a gradient of both thin-film and carbon-supported catalysts. The efficacy of the fuel cell design is evaluated electrochemically to understand which catalyst layer system maximizes fuel diffusion, minimizes hydroxide and hydrogen adsorption, and facilitates the removal of borate from the catalyst layer.
The characteristics of catalyst layer structure/composition before and after testing, and electrochemical efficiency for BOR are observed using several analytical techniques including scanning electron microscopy (SEM), X-Ray energy dispersive spectroscopy (X-EDS), Braunauer-Emmett-Teller sorptometry (BET), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS).
(1) Olu, P. Y.; Bonnefont, A.; Rouhet, M.; Bozdech, S.; Job, N.; Chatenet, M.; Savinova, E. Electrochim. Acta
2015, 179, 637.
(2) Stroman, R. O.; Jackson, G. S. J. Power Sources
2014, 247, 756.
Influence of SnO2 Orientation on Electrocatalytic Activities of Pt/SnO2 Model Electrodes for Methanol Oxidation
Authors: Miyazaki Kohei , Nagase Takahide , Fukutsuka Tomokazu , Abe Takeshi 
Published: February 2020

As an electrocatalyst in fuel cells, carbon-supported platinum (Pt/C) catalysts are widely used, but there are some problems in the degradation of carbon support and CO poisoning of Pt surface. To mitigate these problems, oxides supports are considered to be an alternative support for Pt catalysts. Oxide supports have some advantages to improve the long-term stability and the CO tolerance of electrocatalysts, but the detailed mechanism of oxide supports has not yet been unveiled. In this study, we fabricated Pt/SnO2 model electrodes with controlling SnO2 crystalline orientation.
Pulsed laser deposition (PLD) technique was used for fabricating the SnO2 support oxides. Single crystals of aluminum and titanium oxides were used as a support for SnO2 thin film fabrication. Platinum nanoparticles were deposited on SnO2 film with the arc plasma deposition. Fabricated model electrodes were characterized with X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Electrochemical measurements were performed in an aqueous solution with methanol and perchloric acid. CO stripping voltammetry was also carried out to investigate CO tolerance of model electrodes.
XRD patters show SnO2 thin films had surface orientation of (101), (100), and (110). XPS spectra also show the deposited Pt nanoparticles were metallic and had identical positive shift (~ 0.3 eV). The activities for methanol oxidation were in the following order: Pt/SnO2 (101) > Pt/SnO2 (100) > Pt/SnO2 (110). CO stripping voltammograms also showed similar activities for CO oxidation. Detailed influence and mechanism of surface orientation on catalytic activities will be discussed in the meeting.
Electrocatalysts for Ethanol and Methanol Oxidation Prepared by Ion Beam Assisted Deposition of Platinum and Rare Earths Metals on Carbon Fiber Paper Catalyst Carriers
Authors: Poplavsky Vasily , Dorozhko Alexandr , Matys Vladimir 
Published: February 2020

Active layers of electrocatalysts were prepared by ion beam assisted deposition (IBAD) of platinum and one of rare earth metals (Ce, Gd, Dy, Yb) on the carbon based Toray Carbon Fiber Paper TGP-H-060 T (TorayCFP) and AVCarb® Carbon Fiber Paper Р50 (AVCarbCFP) catalysts carriers with the aim of electrocatalysts production for direct methanol and ethanol oxidation fuel cells (DMFC, DEFC) with polymer membrane electrolyte. Formation of layers in IBAD mode, by means of the deposition of metal and mixing of precipitating layer with the substrate by accelerated (U = 5 kV) ions of the same metal, was carried out. In this process, a neutral fraction of metal vapor and ionized plasma of vacuum pulsed electric arc discharge were used. According to scanning electron microscopy, electron probe microanalysis, X-ray fluorescence analysis and Rutherford backscattering spectrometry investigations atoms of deposited metals, carbon substrates, and oxygen as impurity enter into the composition of layers. The thickness of the prepared catalytic layers is ~30 nm; content of platinum atoms in the layers – ~2×1016 cm–2, or much less than 0.05 mgPt/cm2. Properties of the prepared electrocatalysts were investigated by cyclic voltammetry in 1M CH3OH + 0.5M H2SO4 and 1M C2H5OH + 0.5M H2SO4 solutions. It was established that the prepared electrocatalysts show activity in the processes of electrochemical oxidation of methanol and ethanol. The inclusion of the rare earth metal in the composition of formed layers enhances the activity of electrocatalysts in a multistage process of oxidation of alcohols. Moreover the activity of prepared electrocatalysts in the oxidation of more complex molecules of ethanol is higher than the activity in oxidation reaction of methanol. The advantages of proposed IBAD method are as follows: possibility of forming a cohesive catalytically active layer on a carbon substrate at low platinum consumption; one stage of deposition of each of metals a comparison against multistage traditional chemical methods of catalysts preparation.

Figure 1
Development of Stable Precious Metal-Free Cathodes in Alkaline Fuel Cells
Authors: Grimmer Ilena , Gebetsroither Florian , Pichler Birgit , Grandi Maximilian , Kalal Peter , Iseard Barry , Aronsson Robert , Schenk Alexander , Hacker Viktor 
Published: February 2020

The Alkaline Fuel Cells (AFC) have been well developed in the 1960s for on-board power supply for Apollo missions to the moon. Later, in 1990s, the Polymer Electrolyte Membrane Fuel Cell (PEMFC) replaced the AFC due to their advantages such as a lighter and more compact system attributed to solid membranes as electrolyte. However, AFC systems have now reached new attention due to the necessity of using inexpensive non-precious metal catalysts, which is one of the greatest advantages of alkaline media.
In this work, precious metal-free oxide catalysts are investigated regarding their performance and long-term stability. Electrodes containing these precious metal-free catalysts are designed, manufactured and in-situ characterized in AFC half-cell tests and single-cell measurements.
The main focus lies on increasing the long-term stability of cathodes in alkaline media.
Cathodes are manufactured and tested in half-cells for 10,000 h. Tests are performed at different operating conditions: gases (O2, synthetic air, and ambient air), gas flow and temperature are varied. The influence of the operating conditions on the degradation rate and the stability of the cathodes are evaluated accordingly.
Furthermore, single cell tests are conducted with non-noble metal anodes, thereby achieving a precious metal-free AFC. Especially the activation processes are investigated.
In order to preserve cathode performance, the anode activation is performed separately. Afterwards, the two electrodes are assembled in a custom-made test cell and characterized in fuel cell operation.
For comparison of the performance of this precious metal-free AFC, single cells with platinum based catalysts are operated in parallel test cells. The results of the test series will be presented at the meeting.
(Invited) Probing the Activity of Transition Metal Oxide Nanoparticles Towards the Oxygen Reduction Reaction
Authors: Fermin David , Celorrio Veronica , Calvillo Laura , Russell Andrea E , Granozzi Gaetano 
Published: February 2020

Complex transition metal oxides such as perovskites have been extensively investigated in the context of oxygen electrocatalysis.1,2 These materials represent a vast family of compounds with electronic properties sharply dependent on their composition, crystal phase and oxygen content. Consequently, the establishment of structure-activity relationships is of paramount importance in the search of highly active and chemically stable electrocatalysts for alkaline fuel cells. Indeed, the strongly correlated nature of electrons in these materials, as opposed to metallic phases, introduces a high degree of complexity for material screening from first-principle calculations. We have recently examined a range of lanthanide perovskites (LaBO3, with B: Co, Fe, Cr, Mn and Ni) synthesised by a versatile synthetic method capable of generating nanoparticles with a high degree of phase purity.3 We have shown that Mn based oxides show over two orders of magnitude higher activity than any other perovskite towards the 4-electron oxygen reduction reaction (ORR);3,4,5 a difference significantly larger than recognised in previous studies.2,6

In this contribution, we will investigate the origin of the exceptional activity of Mn based perovskites. Our key hypothesis centres around the fact that Mn sites undergo changes in their redox state at potentials close to the formal ORR potential. These redox transitions are key in the oxygen bond breaking step and the overall reactivity of the material. Our studies are underpinned by detailed analysis of the bulk and surface structure employing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and in-operando X-ray absorption spectroscopy (XAS). We will also show that the intrinsic activity of these materials can be strongly affected by the nature of the A-site7 and the temperature of oxide phase formation.
References:
1- A. Grimaud et al. Nat. Mater. 2016, 15, 121
2- J. Suntivich et al. Nat. Chem. 2011, 3, 647
3- V. Celorrio et al. ChemElectroChem 2016, 3, 283
4- V. Celorrio et al. Catal. Sci. & Technol. 2016, 6, 7231
5- V. Celorrio et al. J. Phys. Chem. C. 2016, 120, 22291
6- K.A. Stoerzinger, ACS Catalysis 2015, 5, 6021
7- V. Celorrio, MRS Commun. 2017, DOI: 10.1557/mrc.2017.22
Effect of pH on the Activity of Hydrogen Oxidation Reaction/Hydrogen Evolution Reaction over PtRu Bimetallic Catalysts
Authors: Nash Jared , Zheng Jie , Xu Bingjun , Yan Yushan 
Published: February 2020

Hydrogen proton exchange membrane fuel cell (PEMFC) powered automobiles have become commercially available, but are still too expensive. Hydroxide exchange membrane fuel cells (HEMFCs) offer the possibility of cheaper non-precious metal catalysts. However, the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) are significantly slower in base than in acid for Pt, Pd, Ir, and Rh1-4. PtRu shows higher HOR/HER activity than Pt5, 6, so understanding the mechanism of the HOR/HER on PtRu is key to developing non-precious metal catalysts for HEMFCs. Using the rotating disk electrode, bimetallic PtRu showed a minimum in the HOR/HER activity, pH relationship (Figure 1). The hydrogen binding energy and the hydroxide binding energy measured from the hydrogen underpotential desorption peak and the CO stripping peak, respectively, did not change significantly with pH. Leaching Ru from the catalyst, it was found that the HOR/HER activity of PtRu remains approximately constant while the Ru content is reduced. When a small amount of Ru is leached from the surface, the activity increases and only after a significant amount of Ru has been removed from the surface/near surface of the catalyst does the activity change. This suggests that the HOR mechanism is not the bifunctional mechanism. The charge transfer coefficient, α, decreases with the Ru content going from 0.8 to 0.5. Fitting the kinetic data with the dual pathway model7 shows that below pH 11, the Heyrovsky and Volmer reaction barriers are comparable and above pH 11, the Volmer step becomes rate determining. It is proposed that Ru can align more oxygen species on the surface giving water a more favorable orientation for the Volmer step to proceed, which results in an increase in activity.

References:

1. Sheng, W., et al., Nature communications
2015,
6.
2. Zheng, J., et al., Science Advances
2016,
2 (3).
3. Durst, J., et al., J Electrochem Soc
2015,
162 (1), F190-F203.
4. Sheng, W., et al., J Electrochem Soc
2010,
157 (11), B1529.
5. Wang, Y., et al., Energy Environ. Sci.
2014,
8 (1), 177-181.
6. Wang, J. X., et al., Scientific Reports
2015,
5, 12220.
7. Elbert, K., et al., ACS Catal
2015, 6764-6772.

Figure 1
Morphological and Compositional Effects of Electrochemically Fabricated Cobalt Phosphide on Water Electrolysis
Authors: Kim Junhyeong , Kim Hyunki , Kim Jung Hwan , Ahn Sang Hyun 
Published: February 2020

Recently, development of alternative energy for future has been under investigation to prevent environmental pollution caused by the huge use of fossil fuels. Among them, hydrogen is known as a clean energy source which does not emit pollutants. Effective hydrogen production using water electrolysis is one of the promising methods due to the simple procedure and high purity of product. However, its high cost limits the practical application of water electrolysis owing to the highly loaded platinum which is known as the best active catalyst for hydrogen evolution reaction (HER) To solve this problem, transition metals based compounds have been investigated as catalysts for HER.
In this study, the cobalt phosphide was fabricated on the carbon paper by using electrodeposition method. The morphology and composition of cobalt phosphide was controlled by bath composition and deposition potential/time. The morphology and composition of prepared CoPx catalyst was characterized by field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Furthermore, transmission electron microscopy was utilized to examine the crystal structure and surface composition of CoPx catalyst at the surface. All electrochemical measurements to explore the HER activity were conducted by using conventional three electrodes cell system with N2-purged 0.5 M H2SO4 electrolyte. The HER catalytic activity and electrochemical surface area of CoPx was measured by using cyclic voltammetry. Especially, the electrochemical surface area was estimated by double layer capacitance measurement varying the scan rates. As a result, it was revealed that the intrinsic HER activity of prepared CoPx catalyst has significant relationship with their morphology and composition. Furthermore, the developed catalyst was adopted as hydrogen-evolving electrode for proton exchange membrane water electrolyzer (PEMWE).
A Novel Fabrication Technique for Electrodes of PEM Water Electrolyzers
Authors: Bühler Melanie , Klose Carolin , Hegge Friedemann , Lickert Thomas , Thiele Simon 
Published: February 2020

State-of-the-art polymer electrolyte membrane water electrolyzers (PEMWEs) are assembled via sandwiching a catalyst coated membrane (CCM) between porous transport layers (PTLs). In this work we investigate electrodes deposited directly on PTLs. Together with the novel fabrication technique ‘direct membrane deposition’ (DMD, Fig 1a-c) - already successfully tested for PEM fuel cells [1,2] – this approach is supposed to lead to high performance MEAs for PEMWE. In DMD the fuel cell is assembled as two half-cells with the gas diffusion layers (GDLs) serving as the base for directly depositing the catalyst and the membrane layer. With this technique contact resistances and mass transport in PEM fuel cells were shown to be substantially improved and a reduction of the noble metal loading was enabled [3].However for the application of DMD a smooth and crack-free electrode surface is required [4]. Since state-of-the-art PTLs like Titanium fiber or powder sinter materials at the anodic side exhibit relatively large pores compared to the size of catalyst particles, the fabrication of a smooth catalyst layer on top of the PTL is the first step to establish the DMD method for PEMWEs (Fig. 1d). In this work we present our latest results on this novel topic and show current challenges and perspectives.
References
[1] M. Klingele et al.: Journal of Materials Chemistry A 3 (2015) 11239 - 11245.
[2] S. Vierrath et al.: Journal of Power Sources 326 (2016) 170 - 175.
[3] M. Breitwieser et al.: Electrochemistry Communications 60 (2015) 168 - 171.
[4] M. Breitwieser et al.: Journal of Power Sources 351 (2015) 145-150.

Figure 1
Membrane Electrode Assembly Design with Various Bifunctional Catalysts in Reversible Anion Exchange Membrane Fuel Cells
Authors: Zhao Shuai , Gupta Shiva , Wu Gang , Xu Hui 
Published: February 2020

Reversible anion exchange membrane fuel cells (AEMFCs) have been widely considered as both energy conversion and energy storage devices due to their low cost and high-energy storage capacity, especially when combined with renewable resources. The oxygen electrode reactions have long been one of the primary limiting factors of AEMFCs because of their sluggish kinetics and high overpotential. In our previous study, bifunctional non-platinum group metal (PGM) electrocatalysts for oxygen reduction and evolution reactions have been developed to lower the overpotential on the oxygen electrode, using hybrid structure of metal oxide supported on advance carbon nanotubes [1], transition metal derived graphene tubes [2] or structurally modified transition metal oxides. In this study, the membrane electrode assemblies (MEAs) of reversible AEMFCs using these non-PGM catalysts were designed exclusively, to be applied in real operating environment.
In addition to hardware and cell component down-selection, catalyst layer composition and distribution with different combination of anion exchange membranes and ionomers were optimized extensively by varying parameters including ionomer/catalyst ratio, catalyst ink solvent, mixing method, deposition method and annealing condition. Both catalyst-coated membrane (CCM) and gas diffusion layer (GDE) configurations were compared. Figure 1 shows the highlights of fuel cell and electrolyzer performance improvements. Fig. 1a indicates higher fuel cell internal resistance but better mass transfer in GDE configuration than that in CCM configuration. Fig. 1b demonstrates that electrolyzer performance was improved at elevated temperature through lowering the resistivity of membrane electrode. Fig. 1c provides the optimized ionomer/catalyst ratio for nickel cobalt oxide in electrolyzer mode. Fig. 1d presents the significant enhancement of anion conductivity in the electrolyzer cell with the assistance of KOH solution. This work may provide systematic design perspectives for bifunctional non-PGM catalyst-based MEA fabrication used for reversible AMFCs.
Figure 1. Fuel cell and electrolyzer performances of reversible AEMFC with under different configurations, temperatures, ionomer/catalyst ratios and electrolyte compositions.

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-EE0006960.

References:

[1] Zhao, Shuai, et al. "Highly durable and active Co3O4 nanocrystals supported on carbon nanotubes as bifunctional electrocatalysts in alkaline media." Applied Catalysis B: Environmental 203 (2017): 138-145.
[2] Gupta, Shiva, et al. "Highly Active and Stable Graphene Tubes Decorated with FeCoNi Alloy Nanoparticles via a Template‐Free Graphitization for Bifunctional Oxygen Reduction and Evolution." Advanced Energy Materials 6.22 (2016).

Figure 1
AEM Electrolysis Progress and Impact on the Cost of Hydrogen
Authors: Ayers Katherine E , Capuano Christopher B , Wiles Luke 
Published: February 2020

Membrane (PEM)-based electrolysis provides an ideal near-term technology to address the growing energy storage demands as intermittent renewable energy becomes more prevalent. While proton exchange membrane (PEM) systems are often viewed as preferred solutions to legacy KOH systems due to the lack of corrosive electrolyte, small footprint, and dynamic operating range due to the ability of the PEM systems to generate hydrogen at differential pressure, they still present capital cost challenges. In particular, the platinum group metal catalysts and valve metals for separator and flow field construction required for stability in the acidic environment become a significant cost driver at scale.
Alkaline exchange membrane (AEM)-based electrolysis is therefore viewed as a potential replacement to the current PEM systems as a means of driving down the high capital cost. This cost reduction is accomplished by replacing the typical high cost catalyst and materials of cell construction with lower cost metals that would corrode in the acidic PEM environments, but are stable in the alkaline chemistries. In theory, this approach is highly promising, but testing of the current state-of the art has shown the technology gaps between the two platforms in terms of stability, durability, and operating electrical efficiency. Modeling has shown that savings realized in capital cost are typically off-set by an increase in operating expense resulting from the lower activity of the non-PGM catalysts and poor conductivity of the AEM. Additionally, thermal instability of the AEMs require stacks to be operated at lower temperatures than a typical PEM system, impacting conductivity further and slowing kinetics.
The addition of liquid electrolyte to the water feed has been shown by some groups to be effective in reducing cell operating potentials and providing overall voltage stability. However, this solution adds management and additional maintenance of handling the caustics typically used. Efforts at Proton have shown significant improvements in operation under milder conditions, showing some potential to achieve targets required to compete with incumbent technology. In this talk, some of the advancements achieved and how these have impacted the cost of the hydrogen will be discussed. An example of this improvement is shown in the figure below, where collaborative ionomer research and partnering with a commercial entity for scale-up of catalyst synthesis have translated into an immediate improvement over targets previously established. Additionally, cost models will be compared to show the path needed to establish equivalence with current PEM systems and what is required to go beyond.

Figure 1