bluuebunny/crossref_metadata_2025_split huggingface dataset:
Importance of Specific Interactions between Support, Metal Oxide Nanostructures and Noble Metal or Organometallic Sites in Efficient Electrocatalytic and Bioelectrocatalytic Reduction of Oxygen
Authors: Kulesza Pawel J. 
Published: February 2020

Systems utilizing carbon nanostructures (e.g. nanotubes) and noble metal nanoparticles can form advanced electrocatalytic materials with well-defined composition, structure and thickness. We explore here the ability of inorganic structures to stabilize and derivatize metal (Au, Pt, Pd) and carbon nanostructures. Among inorganic systems, polyoxometallates of tungsten are attractive since they can not only adsorb irreversibly on solid surfaces but also exhibit reversible stepwise multi-electron transfer reactions. The concept of the layer-by-layer formation of hybrid inorganic assemblies composed of anionic polyoxometallate-protected carbon nanotubes (or metal nanoparticles) and ultra-thin nanostructures of positively charged metal oxide (vanadia, titania, zirconia) nanostructures (alone or in combination with tungsten oxide) will be described and discussed here. The resulting novel composite materials are characterized by fast dynamics of charge propagation. When it comes to the electrocatalytic reduction of oxygen, polyoxometallates can also be applied to stabilize and link Pt, Pd and various alloyed Pt-based catalytic nanoparticles.
To produce bioelectrocatalytic materials for oxygen reduction, we explore unique properties of biofilms, i.e. polymeric aggregates of microorganisms, in which cells adhere to each other on the electrode surfaces. Such systems are characterized by extracellular electron transfers involving c-type cytochromes (heme-containing proteins). Biofilms grown on inert carbon electrode substrates tend to exhibit electrocatalytic properties towards oxygen and hydrogen peroxide reductions in neutral media. The processes have been found to be further enhanced by introduction of multi-walled carbon nanotubes (MCNTs) that are modified with ultra-thin layers of organic (e.g. 4-(pyrrole-l-yl) benzoic acid. We expect here attractive electrostatic interactions between carboxyl-group containing anionic adsorbates and positively charged domains of the biofilm with c-type cytochrome enzymatic sites. Coexistence of the above components leads to synergistic effect that is evident from positive shift of the oxygen reduction voltammetric potentials and significant increase of voltammetric currents. Most likely, the reduction of oxygen has been initiated at the molecular (e.g. intentionally added metalloporphyrin redox centers), whereas the undesirable hydrogen peroxide intermediate are further decomposed at the cytochrome sites.

Acknowledgement

We appreciate collaboration with Krzysztof Miecznikowski, Adam Lewera, Beata Dembinska, Jakub Sek, and Anna Dobrzeniecka from Faculty of Chemistry, University of Warsaw.
Mediated Electron Transfer for ORR Catalysis with Transition-Metal Macrocycles
Authors: Elbaz Lior 
Published: February 2020

The search for a non-precious-metal based, oxygen reduction reaction (ORR) catalysts for fuel cells has grown due to rising prices of the catalysts used today which is derived from their scarcity. Although very active, platinum, which is considered to be the state-of-the-art catalyst for ORR, is not used in biological systems almost at all, especially not in processes which involve the catalysis of ORR. One of the reasons may be availability, another may be reaction selectivity. Instead, biological systems usually use transition metal complexes to catalyze such reactions. These are normally a part of an elaborate system of electron donors, electron acceptors and electron mediators, described in electron transfer chains and cycles. Since the beginning of the search for non-precious-metal catalyst, one family of catalysts has always been interesting as a possible candidate to replace precious metal catalysts – transition metal macrocycles (TMMs). This is due to the significant roles these macrocycles play in biological systems, which in many cases involve ORR catalysis.
In the past years we have worked on the study of the interaction between various TMMs and redox active molecules known as electron donors in catalytic cycles. The interaction between quinones and other possible electron donors such as imidazoles and thiophenes have shown to enhance the ORR activity of TMMs. Figure 1 shows an RRDE measurement obtained with cobalt porphyrin (CoTPPS) interacting with hydroquinone on the surface of carbon electrode. In comparison to its ORR activity without the hydroquinone layer on the carbon (not shown), the CoTPPS’s half wave potential is shifted by more than 400mV to a more positive potential. This shift is attributed to the interaction with the electron donor.
In this talk, we will present our most recent work on the study of the interaction between TMMs and electron donors and its effect on ORR electrocatalysis.
An Efficient Silver-Metal Oxide Hybrid Bifunctional Catalyst for Alkaline Air-Electrodes: DEMS and RRDE Study
Authors: Baltruschat Helmut , Amin Hatem M.A. , Zan Lingxing , Ayata Sevda , Soltani Mohammad 
Published: February 2020

In order to develop a commercial catalyst for metal-air batteries, stability, good round-trip efficiency, high activity and fast kinetics for OER/ORR should be satisfied. Since the high cost of Pt limits its industrial application, several metal oxides of the perovskite and spinel type such as Co3O4 have been tested as bifunctional catalysts.[1] Silver is a non-precious and active catalyst for ORR. Thus, coupling of silver and metal oxide like Co3O4 revealed to be a promising catalyst for both ORR and OER. This carbon-free mixed catalyst showed high activity and good stability in alkaline media. 10% and 20% of Co3O4 was found to be optimum for ORR and OER, respectively. RRDE data showed that ORR follow the direct 4-electron pathway with negligible peroxide formation. About 60mV shift in half wave potential of ORR for the 10% catalyst compared to pure silver was achieved. DEMS results monitored the OER onset. Tafel slopes of about 80 mV/dec at low overpotentials were obtained for the mixed catalysts.
In further model experiments we studied the activity of the spinel on smooth Ag and also other metal electrodes confirming the synegetic effect. Experiments with a variety of perovskites yielded similar results.
References:
[1] F.H.B. Lima, J.F.R. de Castro, E.A. Ticianelli, Journal of power sources 161(2006)806
Preparation of TaOx by Electrochemical Technique and Its Application to Electrocatalytic Oxygen Reduction
Authors: Awaludin Zaenal , Safuan Mohd , Ye Xiao , Okajima Takeyoshi , Ohsaka Takeo 
Published: February 2020

Here we demonstrate a new and simple technique for preparing a tantalum oxide (TaOx)-based electrocatalyst at room temperature for oxygen reduction reaction (ORR) by electrochemical technique [1-4]. The Ta2O5 on the as-prepared deposits was reduced by electrolysis at potential of −0.6 V vs. Ag|AgCl|KCl(sat.) for 12 h generating a smoother and thinner layer of its reduced species (TaOx) (Fig. 1). The treated TaOx exhibits a high ORR activity in acidic and alkaline solutions as seen from a fairly high onset potential (0.87 V vs. RHE) in comparison with that (0.98 V) at a commercially available Pt/C catalyst. By rotating ring-disk electrode voltammetric measurements, it can be concluded that this oxide possesses an almost four-electron ORR electrocatalysis at potential above 0.8 V vs. RHE and a two-electron ORR becomes significant gradually as the potential is increased negatively. The obtained results demonstrate that the present “treated” TaOx is expected as a promising electrocatalyst for ORR in PEMFCs even though its electrocatalytic performance needs to be improved significantly further to replace the Pt/C.

Fig. 1 Schematic illustration of the electrochemical preparation of TaOxelectrocatalyst for ORR.

Acknowledgement

The present research was financially supported by Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

References

1) Z. Awaludin, M. Suzuki, J. Masud, T. Okajima and
T. Ohsaka, J. Phys. Chem. C, 115, 25557 (2011).
2) Z. Awaludin, J.-M. Sheng Moo, T. Okajima and
T. Ohsaka, J. Mater. Chem. A, 1, 14754 (2013).

3) J. G. S. Moo, Z. Awaludin, T. Okajima and T. Ohsaka, J. Solid State Electrochem., 17, 3115 (2013).
4) Z. Awaludin, T. Okajima and T. Ohsaka,

J. Power Sources, in press.
Pt-Lanthanide Alloys for Oxygen Reduction: Relating Active Surface Phase and Catalytic Performance
Authors: Malacrida Paolo , Escudero-Escribano Maria , Verdaguer-Casdevall Arnau , Vej-Hansen Ulrik Grønbjerg , Rossmeisl Jan , Stephens Ifan E. L. , Chorkendorff Ib 
Published: February 2020

The development of economically viable and efficient low temperature fuel cells requires a substantial improvement of the oxygen reduction reaction (ORR) catalysts at the cathode. Alloys of Pt and late transition metals have exhibited high activities, but typically suffer from a fast degradation due to dealloying [1-2]. Not only do polycrystalline alloys of Pt and a lanthanide metal (La, Ce, Gd) exhibit very high catalytic activity, but they should also be inherently more stable than alloys of Pt and late transition metals, due to their very negative heat of alloy formation [3-5]. In this work, sputter-cleaned Pt5La and Pt5Ce present more than a 3-fold activity enhancement compared to polycrystalline Pt with only minor losses after accelerated stability tests (Fig. A). The extensive combination of electrochemical and physical techniques, including Angle Resolved X-Ray Photoelectron Spectroscopy (AR-XPS) and Low Energy Electron Spectroscopy (LEIS) makes these polycrystalline samples excellent model systems towards the design of cathode catalysts. The active chemical phases, which are still largely debated, have been elucidated by AR-XPS (Fig. B). La and Ce oxides are formed on the surface of the alloy under air-exposure but they are readily removed by acid leaching during ORR activity testing. A ~3 monolayer thick Pt overlayer is formed and provides kinetic stability against further dealloying during cycling (Fig. C). Investigating the nanoscale properties of these overlayers is a fundamental step towards understanding their catalytic performance. The level of strain relative to pure Pt is responsible for the enhanced activity. It turns out that the thickness of the overlayer defines the level of strain relaxation and provides details about the dealloying mechanism.
[1] H. A. Gasteiger, et al. Appl. Catal. B
2005, 56, 9. [2] I. E. L. Stephens, et al. Energy Environ. Sci. 2012, 5, 6744. [3] M. Escudero-Escribano, et al. J. Am. Chem. Soc. 2012, 130, 16476. [4] P. Malacrida, et al. J. Mater. Chem. A
2014, 2, 4234. [5] S. J. Yoo, et al. Energy Environ.
Sci. 2012, 5, 7521.
Fig. (A) Kinetic current density measured at 0.9 V of Pt5Ce, Pt5La and Pt before and after a stability test consisting of 10 000 cycles between 0.6 and 1.0 V vs. RHE at 100 mV s−1. (B) Ce 3d XPS spectra of Pt5Ce after electrochemical measurements showing only metallic components. (C) AR-XPS depth profile of Pt5Ce after ORR testing (solid line) and after stability test (dashed line). In the inset, illustrative structure of acid leached Pt5Ce.
Coupling Chemo-Mechanical Oscillators
Authors: Parmananda Punit 
Published: February 2020

The dynamics of a chemo-mechanical
Mercury Beating Heart (MBH) system is
analyzed experimentally.
It is observed that different
shapes of the mercury drop could be
obtained. The redox potential timeseries
for this MBH system, corresponding to these different
shapes were also recorded.
Subsequently, two and three such oscillators were coupled
and the resultant synchronization phenomena studied.
Invited: Non-Equilibrium Effects of Non-Equilibrium Plasmas: From Nanoscale Synthesis to Applications in Energy and Medicine
Authors: Ostrikov Kostya (Ken) 
Published: February 2020

Several examples of the effects of non-equilibrium “extreme” conditions of low-temperature plasmas on the formation and processing of advanced nanomaterials and nanostructures [1,2] and also on the responses of living cells to the plasma exposure [3,4], are presented. The plasma-produced or functionalized nano-materials considered are aimed at next-generation energy, sensing, environmental and several other applications that are of critical importance to the sustainable future of humankind. Plasma-specific effects that lead to these interesting properties and superior performance in the envisaged applications are discussed.
This presentation explains why low-temperature plasmas represent a unique way of producing and arranging a variety of atomic, radical, cluster, etc. building units into a variety of nanoscale objects. It also discusses the effects of atmospheric-pressure plasma treatments on a variety of living cells and tissues and explores some relevant mechanisms that lead to the specific responses. The examples include effective apoptotic pathways of killing various cancer cells, inactivation of various microorganisms and biofilms, as well as agitation of stem cells to achieve selective differentiation.
The nanotechnology-related examples mostly include (but are not limited to) plasma-produced or functionalized nano-carbon materials that are aimed at next-generation in energy, sensing, environmental and several other applications that are of critical importance to the sustainable future of humankind. Plasma-specific effects that lead to these interesting properties and superior performance in the envisaged applications are examined and where possible are related to the non-equilibrium, to some extent “extreme” properties of the plasmas.
[1] K. Ostrikov, Rev. Mod. Phys. 77(2005) 489.
[2] K. Ostrikov, E. C. Neyts, M. Meyyappan, Advances in Physics 62(2013) 113.
[3] M. Ishaq, M. Evans, K. Ostrikov, Int. J. Cancer 134(2014) 1517.
[4] Z. Xiong, S. Zhao, X. Mao, X. Lu, G. He, G. Yang, M. Chen, M. Ishaq, K. Ostrikov, Stem Cell Research 12 (2014) 387.
Development of Li2FeSiO4/Activated Carbon Composited Cathodes for Li-Ion Capacitors
Authors: Li Chun-Lung , Chao Chung-Hsiang , Lee Ying-Hui , Lin Yu-Wei , Hwang Jenn-Yeu , Tsai Li-Duan , Fang Jason 
Published: February 2020

The hybrid supercapacitors are electrochemical energy storage devices that combine the advantages of both Li-ion batteries and supercapacitors. The lithium ion capacitors (LICs), one of the hybrid capacitors under development, has a speciﬁc energy and energy density of around 30 Wh/kg and 20 Wh/L, respectively. These values are more than three times higher than the values of a conventional EDLC.They are expected to bridge the gap between Li-ion cells and supercapacitors and be used to power electric and hybrid vehicles. They can deliver high energy and power densities for short periods with long cycle lives, while operating over a wide range of temperatures with low maintenance costs.
The Li2FeSiO4 is attractive as it not only displays outstanding electrochemical behavior, but it is also the basis for the explosion of substituted derivatives with improved properties. However, Li2FeSiO4 has low electronic and ionic conductivity. Carbon coating is an efﬁcient way to enhance the charge transfer. In this study, carbon coating was carried out by mixing Li2FeSiO4 with a carbon source followed by calcination at high temperature and atmospheric conditions. The Li2FeSiO4/carbon composites are denominated as LFSC1, LFSC2 and LFSC3. The pristine capacities of Li2FeSiO4/carbon composites are measure at different C rate. The LFSC2 shows the best performance at each C rate. The LICs are fabricated with lithium ion battery type anode and LFSC/activated carbon cathode. The performances are measured by battery test equipment with CC-CV charge/CC discharge procedure. The charge/discharge plots show the traditional diagram of supercapacitor. This work is studying by some other approach to achieve high power performance.
Polyanilene-Coated Porous Carbon Nanofiber Electrodes for Supercapacitors
Authors: Kalra Vibha 
Published: February 2020

We report the development of three-dimensional hybrid supercapacitor electrodes combining pseudocapacitive polyanilene and porous carbon nanofibers. The porous carbon nanofibers with specific surface area of >1500 m2/g were first fabricated via electrospinning of a blend of carbon precursor and sacrificial polymer followed by high temperature pyrolysis. The pyrolysis step converted the carbon precursor (polyacrylonitrile-PAN) to carbon and decomposed out the sacrificial polymer forming micro/mesopores within carbon nanofibers. Figure 1 shows the SEM images of porous carbon nanofibers fabricated using different PAN concentrations. Figure 2 shows the CV curves (in 1M H2SO4) of porous carbon nanofibers fabricated using 40 wt% PAN at various scan rates exhibiting ideal rectangular shape indicative of fast ion transport and high power handling capability. Polyanilene was conformally coated on porous carbon nanofiber substrates via electropolymerization of aniline monomer in 1 M H2SO4to develop device-ready freestanding hybrid electrodes. Electropolymerization was carried out in a three-electrode setup using the potentiodynamic method with Ag/AgCl as the reference electrode and platinum mesh as the counter electrode. Figure 3 provides an SEM image showing conformal coating of polyanilene over porous carbon nanofibers. Electrochemical characterization of the hybrid polyanilene/porous carbon nanofiber samples was conducted. Figure 4 shows the CV curve of the hybrid electrodes with 10 wt% polyanilene. CV shows clear polyanilene redox peaks exhibiting transformation from fully reduced leucoemeraldine to half oxidized emeraldine form. CV shows clear retention of electric double layer capacitance in the hybrid electrodes resulting in a total specific capacitance of over 250 F/g based on the weight of the complete electrode (porous carbon substrate and polyanilene).
Figure Captions

Figure 1: SEM images of mesoporous carbon nanofibers fabricated via high temperature calcination of the nanofibers electrospun using different material compositions generating different intra-fiber pore sizes. Scale bars = 500 nm. All samples exhibit >1500 m2/g specific surface area as measured using nitrogen physisorption (not shown).

Figure 2. Cyclic voltammetry curve of porous carbon nanofibers at various scan rates in 1M H2SO4.

Figure 3. SEM image of 10 wt% polyanilene conformally coated over porous carbon nanofibers.

Figure 4. Cyclic voltammetry curve of 10 wt% polyanilene coated over porous carbon nanofibers at 20 mV/s in 1M H2SO4.
Invited: New Generation Supercapacitors in Synergy with Li-Ion Technology
Authors: Naoi Katsuhiko , Naoi Wako 
Published: February 2020

To meet growing demands for electric automotive and regenerative energy storage applications, researchers all over the world have sought to increase the energy density of electrochemical capacitors. Hybridizing battery and capacitor electrodes can overcome the energy density limitation of the conventional electrochemical capacitors because they employ both the system of a battery-like (redox) and a capacitor-like (double-layer) electrode, producing a larger working voltage and capacitance. However, to balance such asymmetric systems, the rates for the redox portion must be substantially increased to the levels of double-layer process, which presents a significant challenge.
An in situ material processing technology called “ultracentrifuging (UC) treatment” has been used to prepare a novel ultrafast Li4Ti5O12 (LTO) nanocrystal electrode for capacitive energy storage. In the present paper, the author will describe an extremely high performance supercapacitor that utilizes highly optimized “nano-nano-LTO/carbon composites” prepared via the UC treatment. The UC-treated LTO nanocrystals are grown as either nanosheets or nanoparticles, and both have hyperlinks to two types of nanocarbons: carbon nanofibers and supergrowth (single-walled) carbon nanotubes. The spinel structured LTO has been prepared with two types of hyperdispersed carbons. The UC treatment at 75000G stoichiometrically accelerates the in situ sol-gel reaction, hydrolysis followed by polycondensation, and further forms, anchors, and grafts the nanoscale LTO precursors onto the carbon matrices. The mechano-chemical sol-gel reaction is followed by a short heat-treatment process in vacuo. This immediate treatment with heat is very important for achieving optimal crystallization, inhibiting oxidative decomposition of carbon matrices, and suppressing agglomeration.
Such nanocrystal composites can store and deliver energy at the highest rate attained to this date. The charge-discharge profiles indicate a very high-sustained capacity of 80 mAh/g at an extremely high rate of 1200 C. Using this ultrafast material, we assembled a hybrid device called a “Nanohybrid capacitor” that consists of a Faradaic Li- intercalating LTO electrode and a non- Faradaic AC electrode employing an ion adsorption-desorption process. The “nanohybrid capacitor” cell has demonstrated remarkable energy, power, and cycleability performance as an electrochemical capacitor electrode. It also exhibits the same ion adsorption-desorption process rates as those of standard activated carbon electrodes in electrochemical capacitors.
The new-generation “Nanohybrid capacitor” technology produced more than triple the energy density of a conventional electrochemical capacitor. Moreover, the synthetic simplicity of the high-performance nanostructures makes it possible to scale them up for large-volume material production and further applications in many other electrochemical energy storage devices.
Study of Y2O3 Thin Film Prepared by Plasma Enhanced Atomic Layer Deposition
Authors: Cho Gu Young , Noh Seungtak , Lee Yoon Ho , Ji Sanghoon , Cha Suk Won 
Published: February 2020

Atomic layer deposition (ALD) is a promised thin film deposition technique to fabricate nanometer scale thin films. Unlike chemical vapor depositions (CVDs), one cycle of ALD process is composed of separated precursor pulsing step, purging step and reactant pulsing step. Due to separated steps in an ALD process, precise thickness control of thin films is available. Step coverage, uniformity and conformality of thin films are also superior compared with other thin film techniques, such as sputter, pulsed laser deposition (PLD).
Plasma enhanced atomic layer deposition (PEALD) is energy reinforced ALD technique by inserting plasma. In case of a direct PEALD, plasma is induced during the reactant step to improve reactivity of reactant. The ALD window of PEALD is expanded especially at lower temperature due to high reactivity of plasma species. Better quality of thin films is available due to decreased contaminations within thin films and improved stoichiometry of thin films.
Y2O3 has wide band gap, good thermal stability, and high dielectric constant. Due to these characteristics, Y2O3 is used for various applications, such as, replacement of SiO2 in complementary metal oxide semiconductor (CMOS) devices, protective coatings, and buffer layers for ferroelectrics and superconductors. Y2O3 is also used to fabricate Yttria-stabilized zirconia (YSZ) which is the most typical electrolyte material for solid oxide fuel cells (SOFCs).
In this study, we prepared Y2O3 thin films by direct PEALD. Tris (methylcyclopentadienyl) yttrium ((MeCp3)3Y) precursor is used as a precursor of Y2O3 and high purity oxygen gas with O2 plasma is used as the reactant. The growth rate of Y2O3 thin films are measured by ellipsometer as a function of deposition temperature. Physical and chemical characteristics of Y2O3 thin films are also investigated which is deposited at different temperature.