bluuebunny/crossref_metadata_2025_split huggingface dataset:
Probing Adsorption on Platinum Group Metals to Understand Fuel Production Via Electrocatalytic Reduction
Authors: Richards Danielle , Akinola James , Liu Jin-Xun , Goldsmith Bryan , Singh Nirala 
Published: February 2020

Renewable electricity generated from solar or wind is inherently intermittent, so finding routes to electrochemically store this energy in chemical bonds as fuels or chemicals is an important scientific challenge. For electrocatalytic reduction reactions such as bio-oil hydrogenation1,2 or nitrate conversion to ammonia,3 the rates and efficiency of converting electricity to energy stored in chemical bonds is related to the surface chemistry steps. A particular challenge in understanding and controlling these surface chemistry steps at a molecular level for electrocatalysis is that the complexity of the liquid phase makes it hard to characterize the catalyst surface and adsorbed species. A further challenge is that it is unclear when insight from first-principles calculations such as density functional theory will apply to electrocatalysis, because modeling solvation and the double layer accurately remains a matter of intense effort.
In this talk we will discuss a few techniques to detect surface coverages and intermediates for aqueous electrocatalytic reduction reactions (i.e., phenol hydrogenation and nitrate reduction), and how these techniques have given insight into observed reaction rates. We will discuss how site counting of adsorbed hydrogen on platinum group metals using cyclic voltammetry can be used to determine reactant species coverages as a function of concentration (Figure 1). We will also compare these results to electrochemical impedance spectroscopy measurements of the change in the double layer with adsorption (i.e., decreases in capacitance due to adsorbed organic molecules). Also, we report results of in situ spectroscopy under reaction conditions, including near edge (XANES) and extended X-ray absorption fine structure (EXAFS) to determine catalyst oxidation state, structure, and adsorbate distances. Time permitting, we will discuss vibrational spectroscopy techniques to understand adsorbed species structure, such as surface enhanced Raman spectroscopy applied in the aqueous phase under electrochemical conditions,4 and our efforts to extend the work in this area to understand the effect of applied potential and catalyst surface for bio-oil hydrogenation. We compare our experimental results to first-principles calculations to show where trends allow us to better understand changes in reactivity with catalyst, and how a combined experimental and computational effort can give insight into the electrocatalyst/electrolyte interface in terms of reactant adsorption.

References

(1) Singh, N.; Song, Y.; Gutiérrez, O. Y.; Camaioni, D. M.; Campbell, C. T.; Lercher, J. A. ACS Catal.
2016, 6 (11).
(2) Song, Y.; Gutiérrez, O. Y.; Herranz, J.; Lercher, J. A. Appl. Catal. B Environ.
2016, 182, 236.
(3) Duca, M.; Koper, M. T. M. Energy Environ. Sci.
2012, 5, 9726.
(4) Weaver, M. J. J. Raman Spectrosc.
2002, 33 (5), 309.

Figure 1
Ammonia Electrochemical Synthesis Using Platinum Ruthenium Alloy at Ambient Pressure and Low Temperature
Authors: Schechter Alex , Manjunatha Revanasiddappa , Karajic Aleksandar 
Published: February 2020

Large scale energy storage from renewable is a critical step for development of CO2 free modern society. Electrical energy conversion to chemical compound is one of the preferred alternatives for grid leveling, photovoltaic and windmills storage applications. Nitrogen (N2) reduction to ammonia (NH3) is being offered as an interesting approach of chemical energy storage solution, due to the properties of ammonia which includes high energy density, liquefaction at relative low pressures (10 bars at room temperature) and availability N2 from air. Nevertheless, the slow electrochemical reduction of N2 to NH3 and low coulombic efficiency are the main herders in promoting nitrogen to ammonia technology.
Ammonia was electrochemically produced from nitrogen and water using a ruthenium-platinum (RuPt) alloy catalyst cathode and a nickel anode under ambient pressure and room temperature. The rate of ammonia formation was 5.1×10-9 gNH3 s-1cm-2 with a 13.2% faradaic efficiency at an applied potential of 0.123 V vs. RHE and it reached 1.1×10-8 gNH3 s-1cm-2 at 0.023 V. Ammonia formation reaction was investigated under selected potentials and temperatures and analyzed. Real-time direct electrochemical mass spectrometry (DEMS) analysis of the evolved gases measured at various applied potentials detected only the mass signals of hydrogen and ammonia, which exhibit intensities increase with overpotentials, with no trace of a hydrazine signal at the full potential range. Compared to metallic ruthenium and platinum catalysts, RuPt showed a an improved kinetic indicating a synergistic effect in the reduction of N2, attributed to proximity of Pt-H and Ru-N sites acting in a co-catalysis mechanism (figure 1). An analysis of these processes and comparison to FeOx based stat of the art catalysts are discussed.
Figure 1. Proposed Cooperative Reaction Mechanism for N2 reduction to NH3 on RuPt

Figure 1
(Invited) Investigating the Photoelectrocatalytic Activity of Titania for Nitrogen Fixation Using Rotating Ring-Disk Electrode Voltammetry
Authors: Hatzell Marta C. , Liu Yu-Hsuan 
Published: February 2020

Reports of photocatalytic nitrogen fixation on titania have surfaced for nearly eight decades [1]. Demonstrations have occurred in both the gas and aqueous phase, and with various environmental conditions (relative humidity, temperature, pressure). Nearly all experimental observations suggest that abiotic nitrogen photofixation may be possible at ambient temperature and pressure [2,3]. This is impactful as it promotes the possibility for nutrient based fertilizer production from environmentally abundant materials (minerals) using only the sun as a source of energy. However, the reaction pathway that results in ammonia production is not well understood. Furthermore, the wide band gap mineral coupled with the location of the band edges, suggest that nitrogen reduction not likely. Here, we aim to investigate photo-catalytic nitrogen fixation by titania in an aqueous environment through a series electrocatalytic rotating ring disk voltammetry experiments. We demonstrate that this experimental approach is effective at discerning the low-level ammonium concentration intrinsic to photocatalytic nitrogen fixation experiments through monitoring the ammonia oxidation peak at the ring electrode. Results show that that no ammonium is detected without illumination with both a rutile and mix-phased titania photocatalyst. With illumination ammonium was detected with the rutile phase titania, but not with the mixed phase photocatalyst. This suggest that mineral phase plays an important role in promoting nitrogen photofixation. Rotating ring disk electrode experiments may provide a new avenue to attain a higher degree of precision for detecting ammonia at low levels from both photo and electrocatalyst.
[1]N. Dhar, E. Seshacharyulu and N. Biswas, Proc. Natl. Acad. Sci., India, 1941,7, 115–131
[2]A. J. Medford and M. C. Hatzell, ACS Catal., 2017, 2624–2643.
[3]G. Schrauzer and T. Guth, J. Am. Chem. Soc. , 1977, 99, 7189–7193.
(Invited) Tailoring Optical and Chemical Properties of Nanotube-Based Nanohybrids
Authors: Martel Richard 
Published: February 2020

Carbon and boron-nitride nanotubes are used as 1D templates to produce nanohybrid materials exhibiting tailored properties for optical imaging. On the one hand, the inner cavity of the nanotube is a confined space to encapsulate molecules and to assemble organic dyes into well-ordered aggregates having preferred alignments, such as head-to-tail structures. It has been shown that these assemblies exhibit enhanced optical effects in Raman and fluorescence spectroscopy and that they are stable in harsh chemical conditions and resistant against photobleaching. [1-3] The external wall of the nanotube can be used, on the other hand, to build stable chemical interfaces to the nanohybrids and control their chemical properties in different media (e.g. dispersion, selective bonding, enhance diffusion, etc.). Together, the inner and outer functions can be used to tailor the chemical and optical properties of the nanohybrids and prepare novel optical nanoprobes for bio-imaging applications.
Here we will review our recent work on the preparation of different nanotube-based nanohybrids made of either carbon or boron-nitride nanotubes for optical imaging. More particularly, we have adapted the functionalization of the carbon nanotubes to work more effectively in biological media and target more selectively cancer cells. We have also made advances towards the preparation of boron-nitride nanotube nanohybrids for fluorescence imaging with visible and near-infrared emissions. Finally, we will present recent results on the preparation and use of the nanotube nanohybrids to probe optically (remotely) the electrochemical transduction of pH in the vicinity of the nanoprobe.
[1] E. Gaufrès et al. Nature Photonics 8, 72–78 (2014)
[2] E. Gaufres et al. ACS Nano 10, 10220-10226 (2016)
[3] C. Allard et al. submitted.
This work is done in collaboration with E. Gaufrès, N. Tang, C. Allard, N. Shoghi, S. K. Mal, R. Nascimento, L. Duarte and L. Gaboury
(Invited) Facile Isolation of Semiconducting Single-Walled Carbon Nanotubes By Flavin-Based Supramolecular Chemistry
Authors: Hashimoto Wataru , Toshimitsu Fumiyuki , Nishida Jin , Staykov Aleksandar , Nakashima Naotoshi 
Published: February 2020

The separation/purification of semiconducting single-walled carbon nanotubes (sem-SWNTs) with high quality is one of the most important issues in the science and technology of carbon nanotubes[1-4]. We have already reported that supramolecular coordination polymer [1] and hydrogen bonding systems [2] as well as use of a flavin molecule [3] are powerful methods for highly efficient adsorbent-free sem-SWNT separation.
Here, we designed and synthesized a flavin with thioalkyl substituent at 7- and 8 positions, then examined its selective sem-SWNT sorting behavior. We have found that the addition of a metal ion formed a complex with the flavin, which enhanced selective (8,6)SWNT sorting.

References

[1] F. Toshimitsu, N. Nakashima, Nature Communications, 2014, 5, art no. 5041.
[2] F. Toshimitsu, N. Nakashima, Sci. Rep., 2015, 5, art. no.18066.
[3] F. Toshimitsu, N. Nakashima, Chem. Eur. J., 2015, 21, 3359-3366.
[4] K. Akazaki, F. Toshimitsu, H. Ozawa, T. Fujigaya, N. Nakashima, J. Am. Chem. Soc.2012, 134, 12700-12707.
(Invited) Methylene Blue Helps to Reveal Selectivity of Carbon Nanotube Affinity to Dispersing Agents
Authors: Bachilo Sergei M. , Zheng Yu , Weisman R. Bruce 
Published: February 2020

Methylene Blue (MB) is a water-soluble dye which can physically absorb on single-wall carbon nanotube (SWCNT) surface. We discovered the dye can quench SWCNT fluorescence when it is added to a SWCNT dispersions in water. At the same time its own fluorescence is quenched. Analyzing the parameters of both these quenching processes we observed that the attachment of the dye to a SWCNT depends strongly on the quality of the SWCNT coating. As a result the quenching of specific SWCNT species can be used as a specific indicator of the species “protection” and its affinity to a dispersing agent.
We have observed that the SWCNT quenching by MB is relatively weak in a case of good ionic surfactants, and such a quenching process does not indicate any specific or unexpected trends. Lowing stability of the protective layer due to lower surfactant concentration or unfavorable pH was causing an increasing quenching. More specific effects were detected with more selective process or SWCNT suspended with single-stranded DNA (ssDNA). Relative quenching of SWCNT species in this case was not constant, and could be used as a measure of adhesion strength or density of the SS-DNA on these species. The process of MB attachment was found to be dynamic, and it be described by an temporal attachment of MB molecules to a SWCNT. A quenching model was developed, resulting in a mathematical description with only two parameters. One of them is the adhesion strength (or binding energy), and another is the available volume (space) near a nanotube surface. The most obvious parameter, the available volume, was increasing in a case of a weaker (sparse or thin) coating of SWCNT surface by ssDNA, that was associated with a lower affinity of such ssDNA type to a SWCVNT species. The volume was becoming much smaller with a good ssDNA-SWCNT affinity, preventing in this way the interaction of the quencher with this SWCNT species.
The studied process has appeared to be a simple and reliable tool for quick comparison of the affinity between specific SWCNT and ssDNA in bulk SWCNT solutions. Physical and mathematical models can also help to understand and analyze a wider variety of interactions between SWCNT and suspending agents or wrappers. The attachment of external ionic molecules, such as MB, may also help in development of SWCNT separation methods.
Highly Flexible Agnw-CNT Sponge
Authors: Kim JaeKeon , Lee Junyeop , Jung Daewoong 
Published: February 2020

Carbon based-nano materials such as fullerene, carbon nanotubes (CNTs) and graphene are nanoscale structures with excellent mechanical and electronic properties. To this end, CNT-based have been considered as sensing materials for optical sensor, chemical sensor, physical sensor and environmental sensors. CNT is widely used as a conductive material for strain sensors that detect changes external forces through electrical signals due to low conductivity.
CNT-based Strain sensors were generally fabricated by transferring the individual or bundles of CNTs to the substrates using spin-coating, spraying, dip coating, and inkjet printing methods [1-2].
CNT-based Strain sensors are only weak bonding due to the van der Waals attraction force. resistance change with applied strain force because slipping of the among CNTs. so Linear changes in electrical properties at low strain, but saturation properties at high strain due to the tunneling resistance of the between CNTs [3].
In This paper, we used Silver nanowire CNT (AgNW-CNT) nanocomposite, has much improved mechanical and electrical properties of the saturation properties at high strain.
As one of the most important conductive materials, Ag nanowires (AgNWs) have recently attracted a lot of attention for potential applications as transparent and flexible electrodes [4].
The nanocomposite was prepared by mixing the Agnw(0.5wt%) and CNT(0.5wt%). Then, the Agnw-CNT Coated at the sponges. This Agnw-CNT Sponge can be deformed into any shapes elastically, sustain large-strain deformations, recover most of the material volume elastically, and resist structural fatigue under cyclic stress conditions.
In order to investigate the reliability and stability of Agnw-CNT Sponge sensor, repeatable tests were conducted using cyclic stretching and releasing. The sensitivity of the Agnw-CNT Sponge sensor was reliable and reproducible with fully returned to its original resistance value and improve the strain transfer, repeatability and linearity of the strain sensor.
[1] Jung et al, J. Vac. Sci. Technol. 32 (2014), 04E107.
[2] Han et al, Microelectron. Eng, 168 (2017), 50-54.
[3] Ning Hu et al, Acta Materialia, 56 (2008), 2029-2936.
[4] Feng Xu et al, Adv. Mater, (2012) , 24 , 5117-5122

Figure 1
Photoluminescence Intensity Fluctuations and Temperature-Dependent Decay Dynamics of Individual Carbon Nanotube Sp
3 Defects
Authors: Kim Younghee , Velizhanin Kirill , He Xiaowei , Sarpkaya Ibrahim , Yomogida Yohei , Tanaka Takeshi , Kataura Hiromichi , Doorn Stephen K. , Htoon Han 
Published: February 2020

Recent demonstration of room temperature, telecommunication wavelength single photon generation by sp
3 defects of single wall carbon nanotubes established these defects as a new class of quantum materials1. However, their practical utilization in development of quantum light sources calls for a significant improvement in their imperfect QY (10-30%). Understanding the nature of the PL intensity fluctuations and decay dynamics is of critical importance to optimize the quantum light emission of SWCNT defects. Aiming toward attaining fundamental understanding necessary for addressing these critical issues, we investigate PL intensity fluctuation and PL decay dynamics of aryl sp
3 defects of (6,5), (7,5), and (10,3) single wall carbon nanotubes (SWCNTs) at temperatures ranging from 300 K to 4 K. In this work we identify the mechanisms responsible for the PL intensity fluctuations by analyzing the correlation between PL intensity fluctuations and PL lifetimes. This fluctuation of exciton occupancy could result from random opening of nonradiative quenching sites intercepting exciton population and/or existence of a fluctuating potential barrier around the defect. Furthermore, by analyzing the temperature dependence of PL intensity and decay dynamics of individual defects based on a kinetic model involving the trapping and de-trapping of excitons by optically allowed and forbidden defect states, we estimate the height of the potential barrier. Our analysis also provides further confirmation of recent DFT simulation results that the emissive sp
3 defect state is accompanied by an energetically higher-lying dark exciton state2.
References
[1] X. He et al., Nat. Photon., 2017, 11, 577
[2] M. Kim et al., J. Phys. Chem. C, 2016, 120, 11268
(Invited) Study of Ion Adsorption-Transfer Mechanisms in Nanoporous Carbon Electrodes: Application to Supercapacitors
Authors: Wu Yih-Chyng , Tsai Wan-Yu , Simon Patrice , Taberna Pierre-Louis 
Published: February 2020

Research into the design of electrolytes of ionic liquids (ILs) for supercapacitor applications has grown in popularity in recent years. Unlike Li batteries where the composition of the electrolyte and the stability must meet several requirements (formation of SEI, electrochemical kinetics), the use of ionic liquids in supercapacitors opens interesting perspectives, in particular thanks to their high electrochemical stability. [1]. In this communication, it will be presented the results of an experimental study conducted using quartz crystal microbalance (eQCM) on nanoporous carbon based electrodes in contact with different electrolytes : neat IL and solvated IL as well as electrolyte mixture. EQCM turns out to be an effective analytic tool to bring new insights regarding the charge compensation mechanisms occurring while polarizing the carbon based electrode. In particular, it will be shown that charge compensation can involve different levels of desolvation of the counter-ions and that co-ions can also be used when the carbon electrode is polarized [2,3,4].
Références :
[1] P. Simon et Y. Gogotsi, Nature Materials, 7 (2008) 845-854.
[2] W.-Y. Tsai et al. JACS 8722−8728 (2014)
[3] J. Griffin et al., Nature Materials, 22 juin 2015 (doi: 10.1038 / nmat4318).
[4] Y.-C. Wu, P.-L. Taberna, P. Simon, Communications en électrochimie. 93, 119-122 (2018).
(Invited) Selected Issues for SiC Mosfet Reliability
Authors: Green Ron , Habersat Daniel , Lelis Aivars 
Published: February 2020

There remain a number of potential reliability issues associated with SiC power MOSFETs that interest the reliability standards community, of which this work will provide an overview of our understanding of three of those issues: (1) threshold-voltage stability; (2) body-diode robustness; and (3) short-circuit current robustness.
A recent survey of commercially-available devices shows a wide range of responses in threshold-voltage stability, which is affected primarily by active charge traps in the near-interfacial region of the insulating gate oxide. Their close proximity to the semiconductor interface leads to a strong time dependence in the direct-tunneling mechanism in response to changes in gate bias, necessitating the need for faster measurements and the maintenance of the stress bias before making post-stress measurements. The observation of the activation of additional traps during bias-temperature stress in older devices underlines the need for additional attention to high-temperature charging effects as well.
It is the case for at least one commercial vendor, that improvement in lower BPD density and enhanced device fabrication have led to significant improvements in body-diode robustness. Earlier vintage devices had showed varying levels of degradation in both the body diode and MOSFET on-state properties following current stress of the body diode, as well as degradation in the off-state drain leakage current.
Experimental results show that both commercially-available planar and trench SiC MOSFETs have suitable short-circuit (SC) withstand times, ranging from 6 to 13 μs at T = 25 °C, VGS = 20 V, and VDS = 600 V. Even when trench devices have an identical rating to planar devices, they likely will have a significantly smaller area and heat conducting volume, contributing to their lower robustness for the same SC test conditions. All the electrical results reported seem to be consistent with thermally-driven failure mechanisms. The official standard test method of a single, long pulse is found to not be as effective as a series of shorter, incremental gate pulses, which more accurately detect failure time, even in the case of latent or delayed failure.
All this work will be presented within the context of standards development within JEDEC, including a number of SiC-focused reliability task groups.
A Numerical Study of the V/III Ratio in the MOCVD Process with Pulsed Injection Method
Authors: Chen Jyh-Chen , Lin Wei-Jie , Hu Chieh 
Published: February 2020

AlN layer grabs lots of attention as a great super lattice layer between Si or sapphire substrate and GaN-based material. V/III ratio in the AlN MOCVD process is regard as an important parameter which causes different AlN growth modes on the substrate surface. The growth mode changes from 3D nucleation to 2D growth while the V/III ratio decreases. On the other hand, the pulsed injection method is applied in the MOCVD process to depress parasitic reaction and improve the quality of the AlN film. However, the growth conditions at the wafer surface are strongly affected by the mass transport in the reactor chamber which depends on the flow pattern and gas phase reaction. The momentum, heat and mass transfers are complicated by the pulse action. Different types of pulse sequences and pulse times are reported for finding a better process condition. Until now, it still depends on the empirical data very much and induces enormous time consumption and financial cost in the chamber design process. A suitable numerical simulation is needed to be developed for overcoming this difficulty.
In this study, a time-dependent numerical model is developed to analysis the flow motion and the heat and mass transfer caused by different pulse conditions. For the case with the TMAl gas mixture maintained a constant and a pulsed NH3 gas mixture, the V/III ratio at the surface of substrate increases with the process time after the pulse of NH3 mixture ejected into the chamber. It approaches to a constant when the time is greater than a certain value. The V/III ratio decreases to zero after the pulse of NH3 mixture ends. The V/III changes quickly in a little time when the pulse of NH3 mixture is turned on or off. When the NH3 and TMAl are pulsed into the chamber alternatively, the V/III ratio at the surface of the substrate keeps increasing after the pulse of NH3 mixture turned on. The V/III ratio decreases to zero after the pulse of NH3 mixture turned off. The V/III ratio does not stay at a certain value like the cases which has the constant supply of TMAl mixture. Based on the variation of V/III ratio at the surface of the substrate, we can predict the history of the growth mode at the surface of the substrate during the process.