bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pentavalent Metal Doped TiO2 As Corrosion-Resistant Electrocatalyst Supports in Polymer Electrolyte Membrane Fuel Cells
Authors: Kodali Mounika , Asset Tristan , Herrera Sergio , He Cheng , Sankarasubramanian Shrihari , Matanovic Ivana , Ramani Vijay , Atanassov Plamen 
Published: February 2020

Although being an extremely promising technology, proton exchange membrane fuel cells (PEMFCs) commercialization is still hindered by several challenges, such as the cathode (where the oxygen reduction reaction – ORR – occurs) catalyst activity and stability. Pt nanoparticles homogeneously distributed over carbon-based supports are state of the art catalyst materials at the cathode. However, carbon supports are particularly susceptible to electrochemical corrosion at high potentials. Hence, support materials with an higher stability are needed [1]. Pt supported on TiO2 shows an improved corrosion resistance for ORR compared to carbon supported catalysts [2]. However, the low intrinsic conductivity of TiO2, as well as the high cost of Pt, require further materials optimization before these technologies can hit the market. Here, we present our results on the modification of the electronic structure of TiO2 by doping with pentavalent metals such as Ta, Nb, W, and Mo to improve the conductivity of the support, as well as stabilize Pt on the support surface.
DFT calculations were performed to understand the band structure of doped M:TiO2 (4 at%, M= Ta, Nb, W, Mo) which shows that these materials will be n-type semiconductors, characteristic of defective or nonstoichiometric oxides [3]. The density of d-states for the Pt supported on M:TiO2 was calculated and compared to that of unsupported Pt as shown in Figure 1, evidencing a shift in the d-band center towards lower values (i.e. for M = Ta (-2.34 eV) < Nb (-2.32 eV) < W (-2.30 eV) < Mo (-2.28 eV)). Shift in the d-band center to lower values reduces the strength by which Pt supported on M:TiO2 binds oxygen, hence increasing its reactivity toward the ORR. Based on these results, we predict Ta:TiO2 will not only possess improved conductivity, but also facilitate ORR reduction similarly to Pt alloyed with Co and Ni [4]. Then, we applied those principles to synthesize, and characterize for the ORR, M:TiO2 supported Pt electrocatalysts.
References:
[1] X. Yu and S. Ye, J. Power Sources., 172(1), 145–154, (2007).
[2] S. Bagheri, N. Muhd Julkapli, and S. Bee Abd Hamid, Sci. World J., 2014, 1–21, (2014).
[3] C. He, S. Sankarasubramanian, I. Matanovic, P. Atanassov, and V. Ramani, ChemSusChem., (2019).
[4] V. Stamenkovic et al., Angew. Chem. Int. Ed., 45(18), 2897–2901, (2006).

Figure 1
Development of Fe/N-Doped Carbon Nanotubes As a Stable Non-Precious Electrocatalyst for Oxygen Reduction Reaction
Authors: Xia Dongsheng , Yang Xin , Kang Feiyu , Li Jia , Gan Lin 
Published: February 2020

Heteroatom-doped carbon materials, particularly carbons co-doped with single atomic transition metals (e.g. Fe) and nitrogen, have emerged as one of the most competitive non-precious electrocatalysts for the cathodic oxygen reduction reaction (ORR) in proton-exchange-membrane fuel cells to replace precious platinum (Pt) catalyst. Most carbon-based non-precious electrocatalysts, however, were built on conventional carbon materials such as activated carbon and more recently metal-organic-framework-derived carbon, both of which feature essential drawbacks of carbon corrosion and low electron conductivity due to their low extent of graphitization.1-2

We report here the direct synthesis of well-defined CNTs co-doped with a high density of Fe-Nx active sites (denoted as Fe-N/CNT) through a solid-phase catalytic growth approach, where Fe precursor catalyzed the growth of CNTs from melamine sponge precursor under NH3 atmosphere and simultaneously doped in-situ into the CNT walls with nitrogen. The atomic structure and electrocatalytic properties of the Fe-N/CNT electrocatalysts were characterized by aberration-corrected scanning transmission electron microcopy, Mößbauer spectroscopy, electrochemical analysis and density functional theory calculations. We further design and synthesis a hierarchical Fe-N/CNT electrocatalyst where primary Fe-N/CNTs are enwrapped with secondary Fe-N/CNTs in order to increase the proportion of the Fe-N/CNT active site. The optimized Fe-N/CNT catalyst featured with a high degree of graphitization and high density of Fe-Nx catalytic sites, demonstrating both high ORR activity and remarkable stability in both half-cell test and a single hydrogen fuel cell membrane-electrode-assembly test.
Reference:
[1] Lefevre M, Proietti E., Jaouen F., Dodelet J. Iron-based catalysts with improved oxygen reduction activity in polymer electrolyte fuel cells. Science, 324, 71-74 (2009).
[2] Chen, YJ. Ji SF., Wang D.S., Li Y.D., Angew Chem Int Ed, 56, 6937-6941 (2017)
[3] Xia D.S., Wang R.Z., Wei Y.P., Gan L., Kang F.Y. Melamine-sponge-derived non-precious fuel cell electrocatalyst with hierarchical pores and tunable nitrogen chemical states for exceptional oxygen reduction reaction activity. Materials Today Energy, 9, 271-278 (2018)
Contamination of Metal Impurities during Hydrogen Evolution/Oxidation Reaction
Authors: Weber Daniel Jochen , Dosche Carsten , Oezaslan Mehtap 
Published: February 2020

One of the most promising fuels in the near future will be hydrogen which should produce only by water
electrolysis.1 Although the kinetics of the hydrogen oxidation/evolution reaction (HOR/HER) on platinum
are extremely fast in acidic media, its catalytic performance tremendously drops by two order of magnitudes
in alkaline media.2

To obtain kinetic parameters of electrochemical reactions, e.g. HOR/HER or oxygen reduction reaction
(ORR), rotating disc electrode (RDE) experiments are the main tool in electrochemistry nowadays.
Although the RDE experiments can be performed very easily, fast and cost-efficiently in the labs, reliable
and reproducible evaluation of catalytic performances of materials remain still a critical challenge. In
particular, various sources of impurities need to take into account and to be eliminated prior to
electrochemical measurements. Not till then, structure-activity relationship of electrochemical reactions can
successfully be uncovered. In this study, we discuss possible contamination on polycrystalline platinum
during HER/HOR in various alkaline electrolyte solutions (KOH, NaOH and LiOH). We evidently show
that the observed contamination is not caused by the used hydrogen (quality of 99.999% vs. 99.9999%) or
by glass corrosion which can be avoided by frequently exchange of electrolyte solution. More importantly,
we point out that trace metals stemmed from commercially available used electrolyte salts quickly deposit
on a pure platinum surface during the initial HOR/HER polarization measurements and dramatically
decrease the electrochemically active Pt surface area (HUPD). In addition, we determined the losses of
HUPD over a broad temperature range in KOH, NaOH and LiOH. Interestingly, by chronoamperometric
investigations on a platinum foil followed by surface-sensitive X-ray photoelectron spectroscopy (XPS)
analysis we could detect qualitatively metal impurities originated from the electrolyte solution. We provide
a chronoamperometric method for further purification of electrolyte solution to reduce the contamination
and thus the HUPD losses after the HOR/HER. In this talk, we show critical approaches and solutions
which enable reliable and reproducible HOR/HER activity measurements on platinum in alkaline media.
References
1. M. T. M. Koper, Nature chemistry, 5, 255 EP - (2013).
2. J. Durst, A. Siebel, C. Simon, F. Hasché, J. Herranz and H. A. Gasteiger, Energy Environ. Sci.,
7(7), 2255–2260 (2014).
Electrodeposition of Graded Metal Coatings on Spherical Mandrels
Authors: Peters Vanessa N. , Horwood Corie , Bhandarkar Neal , Stadermann Michael , Bunn Thomas 
Published: February 2020

Inertial confinement fusion energy research at the National Ignition Facility (NIF) requires the fabrication of hollow metal spherical capsules for the laser-driven fusion reaction. These sub-millimeter diameter capsules must have perfect coating uniformity and a specific gradient density, achieved by plating two metal elements with graded composition. We are investigating electrodeposition to produce hollow metal spheres as opposed to other deposition techniques (i.e. physical vapor deposition, film casting, etc.), because electrodeposition coats faster, more smoothly, with good thickness uniformity, and better grain size control.
Electroplating metals on spheres presents its own specific challenges; the spherical samples must make contact with the electrified cathode, but must also remain in motion during plating to ensure an even coating. Additionally, electroplating on hollow spheres also involves the challenge of keeping the sphere submerged in the electrolyte. These issues were mitigated by enclosing the mandrel in an electrified cage which the electrolyte is flowed through, resulting in intermittent contact of the mandrel with the cathode and continuous flow of fresh electrolyte to the mandrel surface while plating.
We have developed several approaches for electroplating alloys[1] and density gradients on metal spherical mandrels. We will present results from a parametric study that improved coating uniformity, obtained desired thickness, and achieved the required density gradients during electrodeposition.
[1] C. Horwood, M. Stadermann, T.L. Bunn, Metal Alloy ICF Capsules Created by Electrodeposition, Fusion Sci. Technol. 73 (2018) 335–343. doi:10.1080/15361055.2017.1387458.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM Release# LLNL-ABS-748349
Noble Metal Decorated Anodic TiO2 Nanotubes: Excellent (Electro)Catalyst
Authors: Krbal Milos , Sopha Hanna , Zazpe Raul , Prikryl Jan , Ng Siowwoon , Macak Jan M. 
Published: February 2020

The synthesis of highly-ordered nanostructures of valve metal oxides has recently attracted huge scientific and technological interest motivated by their possible use in many applications. The most established member of this group of materials is nanoporous Al2O3, which has been prepared two decades ago by anodic oxidation of Al into perfectly ordered, honeycomb-like porous structures employing suitable electrochemical conditions [1]. Owing to the flexibility of the pore diameter/length and the relative ease of the Al2O3 dissolution, its porous membranes have been since than widely used as template material of choice for a range of materials [2-4].
Self-organized TiO2 nanotube layers have received the highest attention after Al2O3 motivated by its range of applications, including photocatalysis, water splitting, solar cells and biomedical uses. Very significant research efforts have led to reproducible synthesis of self-organized TiO2 nanotube layers by means of anodic oxidation, during which the starting Ti substrate is converted into a highly-ordered nanotubular layer by anodization in suitable electrolytes [5-8]. Many new applications can be derived upon modification of the nanotubes by decoration, filling or coating by secondary materials [9].
Atomic layer deposition (ALD) has been shown to be an effective technique to coat TiO2 nanotube layers homogenously with secondary materials or to decorate them with noble metals [9]. The resulting structures offer many advantages and opportunities in various applications. TiO2 nanotubes in particular appeal as highly ordered electron-conductive supports for noble metal particles.
This presentation will focus in detail on the decoration of the nanotube layers of different aspect ratios by noble metals using ALD. We will show and discuss our recent catalytic results on water splitting [10] and electrocatalytic results on the oxidation of methanol [11].
References:

H. Masuda, K. Fukuda, Science, 268 (1995) 1466.

K. Nielsch, F. Müller, A.-P. Li, U. Gösele, Adv.
Mater. 12 (2000) 582.

H. Asoh et al., J. Electrochem.Soc. 148 (2001) B152.

J. Kolar, J. M. Macak, K. Terabe, T. Wagner, J. Mater. Chem. C, 2 (2014) 349.

J. M. Macak, H. Tsuchiya, P. Schmuki, Angew.
Chem. Int. Ed. 44 (2005) 2100.

J.M. Macak et al., Curr. Opin. Solid State Mater. Sci. 1-2 (2007) 3.

K. Lee, A. Mazare, P. Schmuki, Chem. Rev. 114 (2014) 9385.

J.M. Macak, S. P. Albu, P. Schmuki, Phys.
Stat. Sol. (RRL) 1 (2007) 181.

F. Dvorak et al., Appl. Mater. Today 14 (2019) 1.

J. Yoo et al., Electrochem. Commun. 86 (2018) 6.

V.C. Anitha et al., J. Catal. 365 (2018) 86.
Electrolytes Based on Nanoscale Organic-Inorganic Hybrid Materials (NOHMs)
Authors: Cantillo Nelly M. , Bruce Maria , Hamilton Sara Triana , Foister Shane , Park Ah-Hyung , Zawodzinski Thomas A. 
Published: February 2020

The potential use of nanoparticle organic hybrid materials (NOHM) as electrolytes in redox flow batteries is being explored. NOHMs are composite particles formed by polymers grafted (either ionically or covalently) onto surface-modified inorganic nanoparticles. Such structure has great potential to capture and carry nonpolar electroactive species.1

In this work, the protonation behavior, and the effect NOHM structures have on metal cation uptake is evaluated. Both NOHMs considered in this analysis comprise silica cores ionically grafted with polymer tails. The polymer tails correspond to polyethylimine for the NOHM-I-PEI, and to polyetheramine with a sulfonic acid linker for the NOHM-I-HPE.
Cyclic voltammetry was used to investigate the interaction of the copper species as the concentration of the NOHM of interest increases (Figure 1). NOHM-I-PEI showed inhibition of the oxidation and reduction peaks as the NOHM concentration increased, suggesting the formation of the cuprammonium complex. The formation of this complex was also explored via acid-base titration and UV-Vis.
On the other hand, the dynamics of neat and NOHM-based fluids was explored via NMR. DOSY was used to explore the diffusion coefficients of the pure polymers and the NOHMs.

References

1. Y. Park, C. Petit, P. Han, and A. H. Alissa Park, RSC Adv., 4, 8723–8726 (2014).

Figure 1
Mechanisms of Mobile Ion Hopping in Polymerized Ionic Liquids
Authors: Luo Xubo , Liu Hongjun , Paddison Stephen J. 
Published: February 2020

Polymerized ionic liquids (polyILs) present a subclass of solid polymer electrolytes, where the free ions are mobile while the counter ions are grafted to the polymer chains 1. As a result of their unique chemical and physical properties, polyILs are a new class of materials with potential applications as the electrolytes for battery and fuel cells 2. It is believed that ionic conductivity is dependent on the chemical structures of both the polymer and counter ions 3, which enables us to tune the properties of polyILs.
To systematically study the effects of chemical structure and the choice of ions, molecular dynamics (MD) simulations where undertaken to provide atomic-level information of the ion hopping mechanisms. Four types of hopping were identified as: (1) intrachain; (2) interchain; (3) non-associating free ions; and (4) rattling. To find out the effects of different cationic groups and the length of alkyl tails, simulations were performed for poly(n-alkyl VIm) and poly(n-alkyl VATMA), with the counter ion of TFSI¯. Subsequently, the anion was substituted by Br¯ and BF4¯ for the poly(pentyl VIm) to investigate the effects of anions. Structural properties were analyzed from the results. The numbers of associating cations and chains to the anions were calculated, and the changing in the anion hopping types were found for the systems mentioned above. This quantitative analysis should guide the design of polyILs for electrochemical applications in the future.
(1) Stacy, E. W.; Gainaru, C. P.; Gobet, M.; Wojnarowska, Z.; Bocharova, V.; Greenbaum, S. G.; Sokolov, A. P. Fundamental Limitations of Ionic Conductivity in Polymerized Ionic Liquids. Macromolecules
2018, 51 (21), 8637–8645.
(2) Green, O.; Grubjesic, S.; Lee, S.; Firestone, M. A. The Design of Polymeric Ionic Liquids for the Preparation of Functional Materials. Polym. Rev.
2009, 49 (4), 339–360.
(3) Mecerreyes, D. Polymeric Ionic Liquids: Broadening the Properties and Applications of Polyelectrolytes. Prog. Polym. Sci.
2011, 36 (12), 1629–1648.

Figure 1
(Invited) Spectroscopy Techniques Applied to Operando Characterization of PGM-Free Catalysts for Fuel Cells
Authors: Jaouen Frederic , Li Jingkun , Sougrati Moulay-Tahar , Stievano Lorenzo , Zitolo Andrea 
Published: February 2020

Metal-N-C catalysts (Metal = Fe, Co primarily) are being developed and studied as alternative catalysts to platinum for catalyzing the O2 reduction reaction (ORR), in acidic and alkaline media. The nature of their active sites is still a topic of intense discussions and advanced studies, this class of materials possibly comprising N-doped sites, Metal-Nx moieties and various crystallographic structures. The latter often result from excess metal relative to the number of defect sites in the carbon matrix that may host Metal-Nx moieties.
Improved understanding has been gained first through the combination of controlled synthesis, ex situ spectroscopic characterization and ex-situ structure / activity correlations. More recently, operando and/or in-situ spectroscopic techniques have been applied on novel Metal-NC catalysts to better understand their site formation during pyrolysis, their electronic, spin-state and coordinative environment as a function of electrochemical potential and/or time scales. Operando spectroscopy on such catalysts may also offer a way to distinguish the metal-based sites that are electrochemically accessible from those that aren’t. This is a recognized issue for pyrolysed Metal-N-C materials.
This presentation will focus on the application of X-ray absorption techniques to the operando characterization of Fe and Co in Metal-NC catalysts in various electrochemical conditions, and of what could be learnt additionally to ex situ or post mortem studies. Initial results acquired with operando 57Fe Mössbauer spectroscopy will also be presented and discussed.
Bioelectrochemistry in Undergraduate Curriculum and Research
Authors: Rasmussen Michelle 
Published: February 2020

Electrochemistry has a wide range of uses and applications, but undergraduate students do not appreciate this when the topic is first introduced in General Chemistry. Introducing more electrochemical methods in later chemistry courses can encourage interest in the field. In the chemistry department at Lebanon Valley College, the students first encounter electrochemistry through the typical introduction of redox reactions, the Nernst equation, and galvanic cells. The topic is expanded in Analytical Chemistry for juniors during which the students learn about and perform electroanalyltical methods, including potentiometric analysis, coulometry, amperometry, and voltammetry. Students who choose the advanced elective Chemical Sensors and Biosensors learn about electrochemical sensors as one unit of the course. This unit also includes a section on bioelectrochemical sensors. Students develop a hydrogen peroxide biosensor and use amperometry to evaluate its performance, giving them a better understanding of concepts like limit of detection, sensitivity, and dynamic linear range.
In addition to the chemistry curriculum, students can choose to do electrochemical research in the department. Recent projects include fabricating and evaluating enzyme electrodes for a wide range of biologically relevant molecules, designing self-powered biosensors, and designing a biophotovoltaic device for solar energy conversion with plants. Students gain experience with several electrochemical methods, analysis of electrochemical data, and general lab skills. They are also required to present their work, either in posters or oral presentation, skills that will prepare them for their careers after college.
Overall this combination of curriculum and research leads to more students being interested in electrochemistry. They learn that these methods can be used for every area of chemistry, not just analytical. It has lead to an increase in the number of graduating students who continue working in the field, whether in industry or academia.
Aqueous Exfoliation of Nife LDH/CB to Boost Its Oxygen Evolution Reaction Activity in Alkaline Solutions
Authors: Munonde Tshimangadzo Saddam , Zheng Haitao , Nomngongo Philiswa Nosizo 
Published: February 2020

Water electrolysis has recently progressed as the most efficient and attractive way of producing hydrogen and oxygen gasses [1]. However, to ensure the effective production of hydrogen and oxygen yielding high current densities at a low overpotential, a catalyst is needed. Present advancements in the water electrolysis process have opened pathways leading to the synthesis of a variety of non-precious materials as electrocatalysts in place of precious materials [2,3]. In this work, we present the hydrothermal synthesis of the non-precious NiFe2O4/MoS2/C nanocomposites to be used as a bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for water electrolysis in both alkaline and acidic electrolytes. To increase the conductivity of the NiFe2O4/MoS2/C composite, the material was supported on carbon black. Sonochemistry application was employed as a Post-treatment technique to boost the catalytic activity for NiFe2O4/MoS2/C nanocomposites. The post-treated material showed an intense increase in the catalytic activity of NiFe2O4/MoS2/C nanocomposites. The composites also show comparable activity and durability with commercial Pt/C for HER and RuO2/C for OER.
Keywords: water electrolysis, NiFe2O4/MoS2, post-treatment, catalytic activity.

References

[1] Shi, Y., Zhang, B. (2016).. Chem. Soc. Rev, 45(6), 1529-1541.
[2] Lv, H., Xi, Z., Chen, Z., Guo, S., Yu, Y., Zhu, W., Mu, S. (2015). J. Am. Chem.Soc, 137(18), 5859-5862.
[3] Xu, X., Sun, Y., Qiao, W., Zhang, X., Chen, X., Song, X., Du, Y. (2017). Appl. Surf. Sci., 396, 1520-1527.
Nickel-Rich Layered Oxide Cathodes for Next Generation Lithium Ion Battery
Authors: Aryal Shankar , Durham Jessica L , Lipson Albert L. , Kahvecioglu Feridun Ozgenur 
Published: February 2020

Nickel-rich layered oxide cathodes are getting significant attention because of the attractive initial cycle electrochemical performance, lower cost, and reduced toxicity of lithium ion batteries (LIB). There are factors hindering the stable performance of Ni rich cathodes which include cation mixing after synthesis and/or during electrochemical cycling, oxygen activity at high voltage (≥ 4.3 V), reduced thermal stability and structural distortion during cycling. Stoichiometric LiNiO2 is difficult to synthesize and transforms to multiple crystallographic phases on cycling. The layered oxides of nickel, manganese and cobalt (NMC) are found to be structurally compatible to provide elastic network for lithium deintercalation/intercalation, however the exact role of Mn and Co in NMC cathodes is still not clear. Generally, the change in oxidation state of Ni determines the reversible electrochemical capacity, Co and Mn ions are believed to provide structural stability. Therefore, Ni rich composition with suitable Mn and/or Co doping would be a preferred choice. A series of Ni rich layered oxide cathodes with similar morphology and physical properties have been synthesized to study the effects of Mn and Co doping on the structure and electrochemical performance.
The oxidation state and local environment (bond length, coordination number, thermal disorder) of transition metal ions get changed during charge/discharge cycling. In-situ and ex-situ X-ray absorption spectroscopy (XAS) in which individual elements (Ni, Mn, Co) are probed to scrutinize the electronic state and local geometry. Determining these properties will give insight into the degradation/aging mechanism of Ni rich cathodes.