bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phosphorus-Enhanced Oxygen Reduction Activity and Stability of Commercial Pt/C
Authors: Lu Bang-Au , Tian Na , Zhou Zhi-You , Sun Shi-Gang 
Published: February 2020

In fuel cell technologies, the sluggish kinetics of oxygen reduction reaction (ORR) on the cathode is the main obstacle, and it is thus urgent to develop high-performance catalysts. Recently, the role of surface Pt-OH in the ORR has drawn much attention and the highly active ORR catalysts reported recently show much less surface Pt-OH coverage than pure Pt does. Previously, lots of work have focused on tuning the surface electronic structure of platinum-based catalysts, controlling its interaction with reactants, and thus affects the efficiency.
In this work, we report that Phosphorus adsorption of moderate coverage could substantially enhance the activity and stability of commercial carbon supported Pt electrocatalyst towards oxygen reduction reaction. Compared to pure Pt/C, P-decorated commercial Pt/C exhibited weakened oxygen affinity on the surface, and 8-times higher specific activity and 7-times higher mass activity at 0.9 V. Furthermore, compared to commercial Pt/C, we observed that the stability of phosphorus-decorating commercial Pt/C can be enhanced dramatically. The mass activity loss of phosphorus-decorating commercial Pt/C is only 10%, much smaller than that of Pt/C (51%) after 10,000 potential cycles between 0.6-1.0 V. This study may provide a strategic design of Pt-based efficient ORR catalysts for fuel cells.

Figure 1
The Dual Role of Graphene As a Catalyst Support and Protection Cap for Monolayer Pt Catalysts
Authors: Abdelhafiz Ali , Vitale Adam , Alamgir Faisal M 
Published: February 2020

Production of cost-effective polymer electrolyte membrane (PEM) fuel cell materials has been of a great interest over the past decade. At the cathode side, the oxygen reductionreaction (ORR) is the key reaction, for which Pt remains the most widely used catalyst. In order to leapfrog the current limits to Pt use, three main targets have to be achieved. First, is an enhancement of the catalytic activity per Pt atom; second, is a reduction of Pt loading; and third is an increase the catalyst longevity. Here, we demonstrate the dual role of single graphene layer, both as a growth platform and as a protective cap for 2D Pt monolayers catalysts, where all three targets can be achieved.
Using iterative under potential deposition (UPD), monolayers layers of Pt catalyst are grown on top of a monolayer graphene sheet, supported on 50 nm (111) Au substrate. X-ray absorption spectroscopic (XAS) and transmission electron microscopy (TEM) analysis show that Pt monolayers growth is dictated by the graphene-teplated epitaxy. Intimate contact between Pt/graphene induces a localized compressive strain on Pt monolayers ranges 3-10% with an overall compressive strain of 3.5% according to extended x-ray absorption fine structure (EXAFS) analysis. In addition, cyclic voltammetry (CV) analysis shows Pt monolayers fully wetting ~100 mm2area of graphene under-layer with only a ~1 nm ultra-thin layer of Pt, while avoiding ripening as shown through TEM images. Atomic Force Microscopy (AFM) analysis demonstrates that Pt monolayers prefer to follow Frank-van der Merwe growth (i.e. layer-by-layer growth mode) rather than Volmer-Weber growth (i.e. island growth mode), where root mean square (rms) of surface roughness remains quite similar while increasing Pt loading is increased.
Pt/graphene hybrid catalysts show superior catalytic activity for ORR relative to the graphene-free counterparts. A combination of the graphene-imposed compressive strain and electron transfer, push the Pt d-band center up, lowering the overpotential needed for ORR to occur. The graphene/Pt hybrid also show superior activity towards ORR for all shallow Pt mass loadings relative to graphene-free cases, which can be attributed to the interface strain. Due to their intimate epitaxial contact, graphene and Pt, therefore, form a new hybrid catalyst that outperforms Pt. Furthermore, the graphene/Pt cap hybrid shows the graphene protecting Pt MLs from both dissolution and from ripening, with almost no Pt loss after 1000 fuel cell operating cycles. Our demonstration of a graphene-Pt hybrid opens the door for graphene/metal or metal/graphene architectures with potential applications in, and not limited to, energy, thermo-electric and electronics field.

Figure 1
Synthesizing Highly Active and Stable Electrocatalyst for PEMFC through Composite the Carbon-Titanium Dioxide
Authors: Ji Yunseong , Jeon Yukwon , Cho Yong il , Hwang Ho Jung , Jeon Oksung , Kwon Oh Chan , Kim Jeong Pil , Shul Yong Gun 
Published: February 2020

Fuel cell is one of the most promising electrochemical energy conversion devices which withholds many advantages; high efficiency, high power density, rapid start up, any significant pollutant, etc. Especially, polymer electrolyte membrane fuel cell (PEMFC) has been shown a lot of attention due to its high power density and relatively good portability. Commonly, Pt/C catalyst used as PEMFC catalyst because it has high surface area, high electrical conductivity, and appropriate pore structure. However, carbon support materials suffer from degradation in a harsh operation conditions. Generally, carbon corrosion is occurred on the surface and it makes vacancies under the Pt nanoparticles. This mechanism gives rise to agglomeration and sinter of Pt particles via Ostwald ripening. Consequentially, carbon corrosion brings decreases of the electrochemical surface area (ECSA) and hinder long-term operations. Thus, electrochemically stable support materials need to be developed. Recently, some researchers focus on the metal oxide support as promising materials due to their excellent mechanical strength and inherently higher corrosion resistivity. In these alternative material candidates, TiO2 support shows an excellent durability under severe acidic condition, which provides the possibility to directly use as a support. However, hindrances such as low electrical conductivity, catalytic activity and surface area limits direct usage of TiO2 as a catalyst support. In order to improve these drawbacks, we designed the new catalyst. TiO2 nanofibers are prepared by electrospinning method and platinum nanoparticles are deposited on the support by microwave-assisted polyol method. Lastly, CNT was winded around the catalyst surface to boost up the electrical conductivity. The newly designed CNT-Pt/TiO2 nanocatalyst shows well made a 3D network. As a results, the CNTs are placed on the TiO2 surface as an electric conducting pathway. Furthermore, we found a modified Pt electronic structure that takes advantage of the strong synergetic interactions of TiO2 nanofibers, Pt nanoparticles and winded-CNT. This structure influences on a decrease of the d-band vacancy of Pt due to electron transfer from the support, resulting in an improved oxygen reduction reaction. Therefore, the CNT-Pt/TiO2 nanofiber composite shows superior performance and durability, which is definitely distinguishable at high temperature condition of 120 oC, RH 40% compare to the commercial Pt/C.
(Invited) Catalyst Design for Oxygen Reduction Reaction: Platinum Monometallic, Binary and Ternary Nanocatalyst
Authors: Baranton Stève , Lankiang Styven , Dru Delphine , Bigarré Jannick , Buvat Pierrick , Coutanceau Christophe 
Published: February 2020

Improving design and/or reducing noble metal content in electrocatalysts for fuel cell electrodes while maintaining and/or increasing proton exchange membrane fuel cell (PEMFC) performance in terms of durability and power density are crucial challenges for PEMFC mass market applications.
The formation of platinum alloys with transition metals represents a promising way for improving the activity of Pt-based catalysts [1-3]. Pt based alloys have indeed often demonstrated higher electrocatalytic activity towards ORR than pure platinum.
On the other hand, the structure and morphology of the catalyst [4] also play very important roles in the electrocatalytic efficiency for ORR.
In this context, the present study aims at systematically comparing the catalytic activity and the selectivity towards the ORR of binary and ternary catalysts based on Pt, and Au in order to determine the effects of alloyed metals, in terms of kinetics and selectivity. For this purpose, monometallic Pt/C, binary PtxM1-x/C and ternary PtxAuyMz/C (with M a transition metal) nanocatalysts supported on carbon have been first synthesized by a wet chemical method allowing the synthesis of the whole range of alloys and comprehensively characterized. The morphologies, compositions and structures of the particles were characterized by physical methods (thermogravimetric analysis, transmission electron microscopy, X-ray diffraction, atomic absorption, X-ray photoelectron spectroscopy). Electrochemical active surface areas and surface compositions were estimated by cyclic voltammetry. Electrocatalytic activity and selectivity of catalysts were studied by rotating disc and rotating ring disc electrodes.

Acknowledgement:

The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement #325327 (SMARTCat project) and from the ADEME (French Environment and Energy Management Agency) for its financial support through the EXALAME project.
[1] M.T. Paffet, J.G. Beery, S. Gottesfeld, J. Electrochem. Soc. 135 (1988) 1431–1436.
[2] C. Wang, M. Chi, D. Li, D. van der Vliet, G. Wang, Q. Lin, J. F. Mitchell, K. L. More, N. M. Markovic, V. R. Stamenkovic, ACS Catal. 1 (2011) 1355–1359.
[3] T. Toda, H. Igarashi, H. Uchida, M. Watanabe, J. Electrochem. Soc. 146 (1999) 3750–3756.
[4] D. Alloyeau, C. Mottet, C. Ricolleau, Nanoalloys, London: Springer-Verlag; 2012.
Optimization of Pt Catalyst for Anode/Cathode of PEMFC via Magnetron Sputtering
Authors: Ostroverkh Anna , Dubau Martin , Johanek Viktor , Kus Peter , Khalakhan Ivan , Vaclavu Michal , Fiala Roman , Ostroverkh Yevhenii , Matolin Vladimir 
Published: February 2020

In this study, the performance of the thin film Pt catalyst with loading in the range of 1–200 µg/cm2 prepared by magnetron sputtering was investigated for both anode and cathode sides of a proton exchange membrane fuel cell (PEMFC) in H2/O2 and H2/air modes (see example of anode study in Fig.1). Standard microporous layers comprising carbon nanoparticles and Teflon PTFE and FEP supported gas diffusion layer, as well as their modifications by magnetron deposition of carbon in N2 atmosphere (leading to CNx) followed by plasma etching were used as substrates for Pt deposition (Fig.1 right).
The choice of CNx interlayer was motivated by the higher resistance of the CNx structure as compared to pure C which was determined by a mass-spectrometry analysis of PEMFC exhaust at different cell potentials. Benefits of lower absolute carbon etching rate and at least 0.25 V lower corrosion threshold were found for CNxon both sides of the PEMFC (see Fig. 2 for cathode results).
The anode catalysts with various Pt loadings on all the substrates were tested and compared with a standard state-of-the-art commercial Pt/C reference anode with respect to their efficiency for hydrogen oxidation reaction (HOR; see Fig. 1). Performance up to 1.3 W/cm2 in pure H2 and O2 was achieved for anodes containing Pt loading of 2–10 µg/cm2 on CNx substrate. It is comparable to the performance of a standard commercial Pt/C anode with loadings 200–400 µg/cm2.
The same experiments as for HOR were performed for and oxygen reduction reaction (ORR). In this саsе, cathodes with various Pt loadings were tested. The maximum performance up to 0.54 W/cm2 in pure H2 and O2 was found for cathodes with Pt loadings in the range of 20–100 µg/cm2. The Pt loading of 100 µg/cm2 was found as the limit thickness for the magnetron sputtered thin film, further increase of Pt content leads to efficiency decrease of PEMFC. When PEMFC is switched from H2/O2 to the H2/air, the power is decreased 2.0 to 2.2-times relative to the reference Pt/C powder electrodes and 2.8 to 3.0-times on thin film Pt electrodes.
We have also performed 450-hour durability tests in a pulsed regime of 30min open voltage + 30 min under 400 mA/cm2 load, as well as in the regime of stable 400 mA/cm2load for both anode and cathode sides of the PEMFC with Pt loadings of 2 µg/cm2 and 20 µg/cm2.
Based on our research, the PEMFC with best Pt utilization was found for MEA based on a combination of anode with 2 µg Pt per cm2 and cathode with 10 µg Pt per cm2, yielding the total power density 0.45 W/cm2 for as little as 12 µg/cm2 of total noble metal content.

Figure 1
A Study of Carbonate Formation Kinetics and Morphological Effects Observed on OH- Form of Pfaem When Exposed to Air Containing CO2
Authors: Divekar Ashutosh G , Park Andrew Michael , Owczarczyk Zbyslaw R. , Seifert Soenke , Pivovar Bryan S , Herring Andrew M 
Published: February 2020

For AEMFC OH- form of membrane reacts with CO2 when exposed to air leading to loss in conductivity. The data published by Yanagi et.al.[1] suggest that OH species reacts to form Carbonate/bicarbonate in few minutes and after 2 h the membrane only consists of carbonate and bicarbonate. Although this is an important data to consider the reaction kinetics, morphological properties and equilibrium concentrations are still unknown at different environmental conditions. We have attempted to study the CO2 kinetics and its transient effect on conductivity, water-uptake (or lambda) and morphology when the OH- form of PFAEM membrane is exposed to air which has approx. 400 ppm of CO2. The kinetics was studied by exposing the membrane to controlled environment and titrating it using Warder and Winkler titration methods. We have studied transient change in small angle x-ray scattering patterns when the films are exposed to air at different conditions to study the change in d-spacing of the ionic domains. From SAXS analysis it can be concluded that the intensity of spectrum drops over time and the time of equilibration is higher at higher humidity. It takes few hours for the conductivity to drop to carbonate/bicarbonate level. Ultimately we want to understand the effect of CO2 on membrane from every aspect and possibly help us think about strategies to mitigate the problem.

Keywords: Anionic exchange membrane, Carbonate,bicarbonate,carbon-dioxide, small angle x-ray scattering
Ref:
[1]Yanagi and Fukuta, ECS transactions,16(2008).

Figure 1
Structure and Performance of Fe-N-C PGM-Free Cathode Catalysts Derived By Polymerization-Pyrolysis and Sacrificial Support Method
Authors: Chen Yechuan , Gokhale Rohan Rajeev , Serov Alexey , Artyushkova Kateryna , Atanassov Plamen 
Published: February 2020

Recently numerous metal-nitrogen-carbon type cathode electrocatalysts for fuel cell have been synthesized via different approaches [1]. Among these methods, sacrificial support method (SSM) has been developed at UNM group to prepare iron-nitrogen-carbon (Fe-N-C) platinum group metal free (PGM-free) catalysts for oxygen reduction reaction (ORR) [2-6]. Based on this method, we adopted polymerization pyrolysis (PP) to synthesize novel porous Fe-N-C ORR catalysts.
Pyrolyzing polymers has been widely investigated with different nitrogen contained candidate selection, such as polypyridine [7] and polyaniline [8]. However, it is the first time to synthesize ORR catalyst via pyrolyzing C-N-C backbone pyridine based polymers. By introducing ammonia persulfate into water with well dispersed 2-amino-6-methylpyridine (26AMP) or 2,6-diaminopyridine (26DAP) and silica, well nitrogen-carbon bonded polymers could be prepared. FTIR spectra show that there is no amino group absorption, indicating a thorough three dimensional polymerization. The followed pyrolysis with iron salt, HF washing and second ammonia processing lead to a final nanoporous composite.
These different PP catalysts all have good electrochemical performance. 26AMP based materials have high half-wave potentials in both base and acidic environment, no matter silica is used in polymerization (in situ) or just mixed with polymer before pyrolysis (ex situ). All four 26AMP and 26DAP based materials have competitive peroxide yield, achieving the 2% target of Department of Energy [https://energy.gov/eere/fuelcells/durability-working-group].

Figure 1
Interface-Controlled Synthesis of Platinum-Free Anode Catalyst for Fuel Cells Application
Authors: Ding Wei , Tao Sicheng , Wei Zidong 
Published: February 2020

The ever-growing concerns about global warming and energy security demand the expansion of renewable energy sources as viable alternatives to fossil-fuel-based technologies. In all of these concepts, hydrogen is the key energy carrier and, despite several hurdles that still need to be overcome. Two reactions that will inevitably reign over the hydrogen economy are the HOR and its reverse, the HER. The HOR predominantly finds application in fuel cells, while the HER features in various electrolysers. However, the sluggish kinetics of HER and HOR in a basic environment causes high overpotential and associated large energy consumption, which greatly hinders practical application of alkaline electrolysis and alkaline fuel cell. As a typical example, though platinum (Pt) is generally believed as one of the best electrocatalysts for HER and HOR, its catalytic activity is about two orders of magnitude lower in alkaline environment compared with that in acidic electrolyte. Therefore, it is extremely crucial to synthesize a new HOR catalyst with low cost and high activity for HOR in alkaline environment to replace Pt in FCs.
The key to develop a highly active Pt-free HOR catalysts in alkaline environment is constructing a catalytic interface with suitable hydrogen (H) and hydroxyl (OH) binding energies (HBE). Such interface can promote the desorption of Had intermediate and depress adsorption of hydroxyl species. Herein, we report a synthetic method of Ru NPs with strong oxidation resistance and high activity for HOR in alkaline media, by using TiO2 to construct an interface with controlled H and OH binding energy. Our results show that the low-cost RuTiO2/C catalyst exihits an excellent HOR catalytic activity for HOR which is much better than that of Pt based catalysts. This opens a new way to tuning the catalyst interface for the preparation of high performance HEMFC anode catalysts.

Figure 1
Electrochemical De-Hydrogenation of Liquid MCH at Room Temperature
Authors: Badar Saifullah , Kanou Manabu , Nakata Yuki , Nam Hyunjeong , Zenitani Yuji 
Published: February 2020

Hydrogen is a potential candidate for energy carrier role with high gravimetric energy density of 33kWh/kg. However, owing to its low volumetric energy density, 0.003kWh/l at STP, which is very small compared to common fuels, it poses logistical barriers in its widespread use. Conventional methods of hydrogen storage and transportation include compression up to pressures near ~80MPa or liquefaction by cooling down to temperatures below -253˚C. Another promising method of hydrogen storage is to chemically store in the form of organic hydrides. One such organic hydride is methyl-cyclo hexane (MCH), which is liquid at standard temperature and pressure and can be reversibly hydrogenated and de-hydrogenated for storage and extraction of hydrogen, respectively.
Extraction of hydrogen from MCH through dehydrogenation is an endothermic process (ΔH=204.8kJ/mol), so to favor hydrogen production the reaction is carried out at high temperatures. Conventionally, this is carried out in chemical plant sized reactors at temperatures near ~350˚C [1]. Maintaining such a high temperature in small scale energy devices increases the cost and complexity. Hence it is difficult to carry out dehydrogenation locally within the energy devices which utilize the thus extracted hydrogen. A low temperature (<120˚C) and low pressure (~1atm) dehydrogenation process able to be carried out in small scale devices can herald widespread use of MCH as a hydrogen carrier. This will promote hydrogen as a viable option to conventional fuels.
In this study, we have demonstrated the dehydrogenation of MCH at room temperature and pressure using polymer electrolyte membrane (PEM) based electrochemical cell. By applying a potential across the membrane electrode assembly (MEA), consisting of carbon supported catalyst electrode as anode and cathode, hydrogen evolution was observed at cathode side with the supply of MCH at the anode. Quinones have been used as reaction mediator to lower the electrode potential required for the dehydrogenation of liquid MCH to below the water electrolysis potential (1.23V). Formation of toluene as a dehydrogenation by-product at anode was also confirmed using gas chromatography mass spectrometry (GC-MS) analysis. Effect of temperature variation and anode reactant flow rate has been investigated.
References

F. Buonomo, D. Sanfilippo, F. Trifirò, in: G. Ertl, H. Knözinger, J. Weitkamp (Eds.), Handbook of Heterogeneous Catalysis, vol. 5, VCH, Weinheim, 1997, p. 2140
(Invited) From Discovery through to Commercialization: Federal Support
Authors: Madsen Lynnette D 
Published: February 2020

As a Program Director at the National Science Foundation (NSF) working in the Mathematical and Physical Sciences Directorate, most efforts deal with supporting the discovery aspects of science – creating/revealing new materials or phenomena, improving the understanding of scientific underpinnings, and/or establishing new techniques and approaches. However, many NSF programmatic funding opportunities have an option to link to industrial partners through a mechanism called Grant Opportunities for Academic Liaison with Industry (GOALI). Also, there are centers across NSF that foster partnerships with industry; some include mandates to do so. The locus on going beyond discovery to applications at NSF lies within the Engineering Directorate, particularly in the Division of Industrial Innovation and Partnerships (IIP).
NSF is not alone in these undertakings; many Federal agencies have such efforts. The recently released 2016 National Academies report, Triennial Review of the National Nanotechnology Initiative (https://doi.org/10.17226/23603) summarizes many of these efforts to address technology transition. The Nanotechnology Innovation and Commercialization Ecosystem (NICE) Working Group chartered by the Nanoscale Science, Engineering, and Technology (NSET) Subcommittee (https://www.nano.gov/about-nni/working-groups) is interested in further identification of activities to improve technology exchange across the 20 Federal departments and independent agencies engaged in the National Nanotechnology Initiative (NNI).
This region between discovery and commercialization is often described in some circles as the Valley of Death – however, the National Institutes of Health discusses stages from basic science research through four translational phases: humans, patients, practice, and community where each occurs in conjunction with clinical trials. The assortment of programs available reflects the different agency missions, their attention to pinpointing specific hurdles in the process, and the importance of realizing economic benefits from the research. One example, the Small Business Technology Transfer (STTR) program, fosters technology transfer through cooperative R&D between research institutions and small businesses. Participating organizations include the Department of Defense (DOD), Department of Energy (DOE), Department of Health and Human Services (HHS), National Aeronautics and Space Administration (NASA) and NSF. Another example, Innovation Corps (I-Corps), teaches grantees to identify valuable product opportunities that can emerge from academic research, and offers entrepreneurship training facilitated by domain experts. Both NSF and NIH participate. These and other model programs will be discussed.