bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functionalization of Gallium Phosphide Surface with an Organic Monolayer for Advanced Photoelectrochemistry
Authors: Hlynchuk Sofiya , Maldonado Stephen 
Published: February 2020

This work presents progress in the development of stable gallium phosphide (GaP) interfaces capable of undergoing subsequent reactions by introducing an organic monolayer. The context of this work is the use of p-GaP in a fuel forming photoelectrochemical cell. Semiconductor photoelectrodes require specific bulk and surface properties. Gallium phosphide has a band gap of 2.26 eV that allows for absorption in the visible range while the band edge positions make processes like hydrogen and carbon dioxide reduction possible. However, the surface is susceptible to rapid degradation via formation of a native oxide. Surface functionalization techniques provide means to passivate the semiconductor/liquid interface against degradation. In addition, by introducing organic monolayers on semiconductor surfaces subsequent reactions can be performed to further tailor the semiconductor interface as desired. This work focuses on using Grignard chemistry to chemically passivate the gallium phosphide surface via a formation of a gallium-carbon bond. To further alter the interface, reactive handles consisting of either hydroxyl or amine groups are introduced. These functional groups are used to covalently couple dyes to the gallium phosphide previously shown to photosensitize the semiconductor. The stability of the covalent attachment is investigate as a function of pH. Covalent attachment is showed using X-ray photoelectron spectroscopy while gallium phosphide dye sensitization is probed by analyzing the photoresponse pass the band gap.
(Invited) Gate-All-Around Transistors Based on Vertically Stacked Si Nanowires
Authors: Mertens Hans , Ritzenthaler Romain , Hikavyy Andriy Yakovitch , Kim Min-Soo , Tao Zheng , Wostyn Kurt , Schram Tom , Kunnen Eddy , Ragnarsson Lars-Åke , Dekkers Harold F. W. , Hopf Toby , Devriendt Katia , Tsvetanova Diana , Chew Soon Aik , Kikuchi Yoshiaki , Van Besien Els , Rosseel Erik , Mannaert Geert , De Keersgieter An , Chasin Adrian , Kubicek Stefan , Dangol Anish , Demuynck Steven , Barla Kathy , Mocuta Dan , Horiguchi Naoto 
Published: February 2020

Gate-all-around (GAA) transistors based on vertically stacked horizontal nanowires are promising candidates to replace FinFETs in future CMOS technology nodes. First of all, GAA devices provide optimal electrostatic control over semiconducting nanowire channels, which enables downscaling of the gate length to below the FinFET limit, while maintaining low off-state leakage [1]. Besides, horizontally oriented nanowires are an evolutionary extension of FinFETs, as opposed to vertical nanowires which require more disruptive technology and design changes [2]. Finally, stacking of nanowires is relevant for enhancing the drive current per footprint. Based on these considerations, GAA transistors made of vertically stacked horizontal nanowires have been included in the ITRS roadmap to reduce the contacted gate pitch, which is a key figure of merit for CMOS device density, to below ~40 nm in 2019-2021 [3].
In the context of the industrial relevance described above, we present the fabrication of Si GAA devices on bulk Si substrates. Multiple processing aspects that are relevant for bulk CMOS technology definition are addressed, including stacking of 8-nm-diameter Si wires at 45-nm lateral pitch and 20-nm vertical pitch [4], and nanowire-compatible replacement metal gate processing in combination with threshold voltage tuning by dual work function metal integration [5]. Temperature restrictions for the formation of shallow trench isolation, and the interaction between N- and P-type junction formation on one hand and nanowire release processes on the other hand are discussed as well.
[1] K. J. Kuhn, IEEE Trans. Electron Devices, vol. 59 (7), p.1813, (2012).
[2] L. Liebmann et al., VLSI Tech. Dig., p.112 (2016).
[3] The International Roadmap for Semiconductors (ITRS) 2.0, http://www.itrs2.net/ (2015).
[4] H. Mertens et al., VLSI Tech. Dig., p.158 (2016).
[5] H. Mertens et al., IEDM Tech. Dig., p.524 (2016).

Figure 1
(Invited) Atomic Layer Etching of SiO2 and Other Materials Using Plasma Process Sequences
Authors: Oehrlein Gottlieb S. 
Published: February 2020

Angstrom-level precision in etching of SiO2 is possible using steady-state Ar plasma in conjunction with periodic injection of a defined number of C4F8 molecules and synchronized plasma-based Ar+ ion bombardment.1 The physical sputter rate of SiO2 vanishes for Ar+ ion bombardment with a maximum ion energy of 20 eV and lower, whereas for a fluoroccarbon-coated SiO2 surface, chemical modifications of the SiO2 surface are induced by low energy ion bombardment and SiO2 etching is initiated. The question of SiO2:Si3N4 etching selectivity was studied and evaluated with regard to the dependence on maximum ion energy, etching step length (ESL), FC surface coverage, and precursor selection. Since Si3N4 has a lower physical sputtering energy threshold than SiO2, Si3N4 physical sputtering can take place after exhausting the chemical etchant at the end of each cycle for certain ion energies and leads to Si3N4/SiO2 etching selectivity. By optimization of the ALE process parameters, e.g. low ion energies, ESL, and FC film deposition per cycle, highly selective SiO2 to Si3N4 etching can be achieved for conditions where FC selectively accumulates on Si3N4 surfaces.2Mechanism of the observed ALE behaviors will be discussed using real-time and post-plasma surface analysis data. We will also discuss current challenges with the application of these approaches to other materials.

Acknowledgements: I am pleased to acknowledge the essential contributions and collaboration of D. Metzler, C. Li, S. Engelmann, R. Bruce, E. Joseph, C. S. Lai, and E. A. Hudson to this work, and thank National Science Foundation (CBET-1134273), US Department of Energy (DE-SC0001939) and Semiconductor Research Corporation for funding.

1 D. Metzler, R. Bruce, S. Engelmann, E. A. Joseph, and G. S. Oehrlein, J. Vac. Sci. Technol. A 32, 020603 (2014).

2 C. Li, D. Metzler, C. S. Lai, E. A. Hudson, and G. S. Oehrlein, J. Vac. Sci. Technol. A 34, 041307 (2016).
Water Management in Low Temperature Fuel Cells through in-Operando X-Ray Computed Tomography
Authors: Normile Stanley J. , Calzada Osvaldo , Mandal Pratiti , Parkinson Dilworth Y. , Xiao Xianghui , Weber Adam Z , Zenyuk Iryna V. 
Published: February 2020

For polymer-electrolyte fuel cells (PEFCs) and anion exchange membrane fuel cells (AEMFCs) optimal water management is essential. During start-up and at low operating temperatures, where water is present in a liquid form, it can block reactant delivery to electrocatalyst sites, resulting in significant mass-transport losses, flooding and low fuel cell power densities. Using synchrotron X-ray computed tomography (CT) we have previously shown how water transport properties depend on porous materials morphology and chemical composition, as well as cell compression.1-3 These ex- and in-situ studies isolate specific porous membrane / electrode assembly (MEA) component’s effect on water management (such as micro-porous (MPL) or gas-diffusion layer (GDL)). To understand water transport under operating conditions we use in-operandoX-ray CT studies, where water distribution is observed under various steady-state conditions.

In-operando single serpentine channel (1x1 mm) fuel cell testing hardware for synchrotron X-ray CT is used with active area of 1 cm2. Steady-state water generation and removal is observed in PEFCs and AEMFCs for temperature of 30oC with chronoamperometric holds at current densities ranges of 20 – 100 mA/cm2. Furthermore, comparison of water distribution in PGM and PGM-free catalysts for both type of fuel-cells will be presented. In all of these systems water pooling is observed at the component interfaces, indicating the importance of interfaces design.
Acknowledgment: The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
References:
1. I. V. Zenyuk, D. Y. Parkinson, L. G. Connolly and A. Z. Weber, Journal of Power Sources, 2016, 328, 364-376.
2. I. V. Zenyuk, D. Y. Parkinson, G. Hwang and A. Z. Weber, Electrochemistry Communications, 2015, 53, 24-28.
3. I. V. Zenyuk and A. Z. Weber, ECS Transactions, 2015, 69, 1253-1265.
Figure 1. In-operando cross-section tomograph of serpentine channel AEMFC operating at 30 mA/cm2, 30oC and 100 % RH.

Figure 1
Effects of Carbon Supports on the Stability of Pt and PtCo Nanoparticles in PEMFC Cathodes
Authors: Yarlagadda Venkata , Padgett Elliot , Kukreja Ratandeep S , Ziegelbauer Joseph M. , Braaten Jonathan , Ogawa Shohei , Komini Babu Siddharth , Arisetty Srikanth , Gu Wenbin , Thompson Levi T , Litster Shawn , Muller David A. , Kongkanand Anusorn 
Published: February 2020

The drive to reduce the Pt loading in the PEMFC cathode in order to minimize the overall Pt in the fuel cell system below 10-15 g Pt/vehicle requires a durable and stable catalyst that has desirable characteristics such as high activity and low oxygen and proton transport resistances. The carbon support plays an important role in determining the catalyst nanoparticle distribution and transport properties in the electrodes. Therefore, it is vital to understand the degradation mechanisms of both the Pt and carbon support to develop better PEMFC cathodes for automotive applications.
In this study, we evaluated the performance and morphological changes after voltage-cycling accelerated stability tests for Pt and PtCo catalysts supported on different carbon supports. Among the catalysts with different carbon supports, it was found that although the Pt surface area loss, strongly related to Pt dissolution, was comparable, the losses in oxygen reduction kinetics and fuel cell performance for catalysts with high-surface-area carbon were smaller. We studied and will report changes in electrochemical properties, Pt and Co redistribution, and electrode morphology. Simulation to illustrate the stability differences will also be discussed.
This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.
Novel Liquid/Gas Diffusion Layers with Micro/Nano Surface Modifications for High-Efficiency Water Electrolysis
Authors: Zhang Feng-Yuan 
Published: February 2020

Novel Liquid/Gas Diffusion Layers with Micro/nano Surface Modifications for High-efficiency Water Electrolysis

Zhenye Kang[1], Jingke Mo1, Gaoqiang Yang1, Scott T. Retterer[2], David A. Cullen2, and Feng-Yuan Zhang*1

Abstract
Proton exchange membrane (PEM) water electrolysis coupled with renewable sources is considered one of the most practical and high-efficiency methods to produce pure hydrogen. The liquid/gas diffusion layers (LGDLs), which located between the catalyst layer (CL) and bipolar plate, are expected to transport electrons, heat, and reactants/products with minimum losses. Due to the harsh environment at anode of PEMECs, most materials, including carbon and stainless steel, can be easily corroded, which significantly affects the performance and durability of PEMECs. Titanium based thin/well-tunable LGDLs have many advantages, such as high corrosion resistance, small thickness (25 µm), well-controlled pore shape, pore size and pore distribution. Most importantly, it can achieve superior multifunctional performance in low temperature PEMECs, which significantly improves the PEMEC efficiency. In this study, the novel thin/well-tunable LGDLs with different pore morphologies and surface modifications are comprehensively investigated in order to enhance the PEMEC performance. Gold (Au) is deposited on the surface of the thin/well-tunable LGDLs by different micro/nano surface modification methods, and the surfaces of the LGDLs are both ex-situ characterized and in-situ investigated. In addition, the performance and electrochemical impedance spectroscopy (EIS) of the PEMECs with different LGDLs are experimentally investigated and analyzed.

[1] Nano HELP, Department of Mechanical, Aerospace & Biomedical Engineering, UT Space Institute, University of Tennessee, Knoxville, USA.
[2] Oak Ridge National Lab, USA
* Contacting Author: E-mail: fzhang@utk.edu; Tel: +1-(931)-393-7428
New High Potential Membrane Material (For Electrochemical Hydrogen Compression)
Authors: Koeman Menno , Bouwman Peter Jaime , Sikkema Doetze , Mulder Martijn J.J. , Raymakers Leonard F.J.M. , Dalhuijsen Wouter , Semerel Daniel , Konink Jonne , Bosch Melissa , Bleekman Joris J. M. 
Published: February 2020

The company HyET has been working since 2008 on electro chemical hydrogen compression technology. Previously HyET demonstrated as one of the first companies a compression record showing pressures as high as 100MPa in one single stage using EHC.
When using commercial membranes the energy demand for reaching higher pressures has been unfavourable considering the proton conductivity, back diffusion and mechanical properties. From the start HyET has been involved in the membrane development to better understand the requirements in EHC environment and have an angle how to achieve the best performance and durability.
Now a new, fully aromatic hydrocarbon, membrane has been developed which was tested at HyET facilities, and results indicate that compared to commercial reference materials this seems to have game-changing properties. More efficient compression was achieved enabling higher throughput and minimising parasitic losses (back diffusion), thus reducing the operation cost significantly for hydrogen compression. Besides its use in the electrochemical compressor, the newly developed membrane may also prove to have merit in other electrochemical applications, such as electrolysers and fuel cells.
This presentation will show results on the enhanced performance, providing insight in the solutions/benefits for EHC technology and show a method for characterisation of new membrane materials that bring great potential to the future of EHC technology.

Figure 1
Selective Electrocatalytic CO2 Reduction to CO on Solid Nickel-Nitrogen-Doped Carbon Catalysts
Authors: Leonard Nathaniel , Ju Wen , Varela Ana Sofia , Steinberg Julian , Strasser Peter 
Published: February 2020

Electrochemical reduction represents a potential solution for converting carbon dioxide into more valuable products. One application for the carbon dioxide reduction reaction (CO2RR) would be carbon monoxide production, which is a valuable fuel and chemical precursor. An important challenge for commercialization of this process has been finding inexpensive catalysts with a high selectivity to carbon monoxide production. The selectivity towards carbon monoxide production is limited both by the competing hydrogen evolution reaction and poisoning caused by strong binding of carbon monoxide[1-2]. Initial work on non-precious metal CO2RR catalysts was based on iron-based metal-nitrogen-carbon (MNC) catalysts that were originally developed for the oxygen reduction reaction but have also shown strong CO generation performance [1, 3-5]. In the present work a Nickel based MNC catalyst is shown to have higher CO-production rates and less CO-poisoning in comparison to the iron-based MNC catalysts.
In order to make this comparison, a family of catalysts is synthesized by the polymerization of nitrogen precursors around a carbon support and metal precursor [1, 6-7]. Upon heat treatment at 900 °C and subsequent acid washes, a nitrogen-rich, metal-nitrogen-carbon matrix is synthesized. These catalysts are characterized physically and electrochemically. In this work the nickel-based MNC catalyst is shown to be a significant improvement over the Fe-based catalysts and other non-precious metal alternatives. Although the iron-based catalyst shows lower onset overpotential, the nickel-based catalyst has higher peak currents and a longer lifetime.
In this work it is found that the higher current densities and longer lifetime are a result of increased resistance to CO-poisoning. Furthermore, the CO-poisoning allows in situ confirmation of active site quantification via carbon monoxide adsorption techniques. Ultimately, these findings allow optimization of MNC catalysts resulting in high performance non-precious metal catalysts for CO2RR.
References:
[1.] Varela, A. S.; Sahraie, N. R.; Steinberg, J.; Ju, W.; Oh, H. S.; Strasser, P., Angew Chem Int Edit
2015,
54 (37), 10758-10762.
[2.] Tripkovic, V.; Vanin, M.; Karamad, M.; Bjorketun, M. E.; Jacobsen, K. W.; Thygesen, K. S.; Rossmeisl, J., J Phys Chem C
2013,
117 (18), 9187-9195.
[3.] Sahraie, N. R.; Paraknowitsch, J. P.; Gobel, C.; Thomas, A.; Strasser, P., J Am Chem Soc
2014,
136 (41), 14486-14497.
[4.] Hao, G. P.; Sahraie, N. R.; Zhang, Q.; Krause, S.; Oschatz, M.; Bachmatiuk, A.; Strasser, P.; Kaskel, S., Chem Commun
2015,
51 (97), 17285-17288.
[5.] Gong, X.; Liu, S. S.; Ouyang, C. Y.; Strasser, P.; Yang, R. Z., Acs Catal
2015,
5 (2), 920-927.
[6.] Gang Wu, K. L. M., Christina M. Johnston, Piotr Zelenay, Science
2011,
332, 443-447.
[7.] Sahraie, N. R.; Kramm, U. I.; Steinberg, J.; Zhang, Y. J.; Thomas, A.; Reier, T.; Paraknowitsch, J. P.; Strasser, P., Nature communications
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6.
(Invited) The Importance of the Cathode Catalyst Support in the Pursuit of Low-Cost PEM Fuel Cells
Authors: Gu Wenbin , Kongkanand Anusorn , Yarlagadda Venkata , Yu Paul Taichiang , Mathias Mark 
Published: February 2020

Because fuel cells are sized based on their high-power requirement, improvements in the high-power capability (W/cm2) can directly be translated to reduced active area and thus reduced cost. For proton-exchange-membrane (PEM) fuel cells, state-of-the-art PtCo catalysts on several different carbon supports have exhibited impressive and similar kinetic (low-current-density) activity. However, it is now becoming clear that the carbon-support selection can be important in determining their high-power performance. At beginning of life, we have recently observed that active nanoparticles reside predominantly within some porous carbon support particles and are apparently shielded from direct contact with the solid ionomer electrolyte as shown in the second illustration in Figure 1. This raises questions involving O2 and proton transport mechanisms and possible rate limitations within these primary carbon particles.
In this work, we will present a mathematical model that includes the cathode-reactant-transport processes within a porous carbon support, allowing estimation of Pt utilization as a function of material parameters and operating conditions. We will also report recent experimental work that we are bringing alongside the model in attempts to validate and develop it further. Finally, we will discuss the implications for optimizing the support and the active-material location within it.
References
1) E. Padgett et al., Proceeding of Microscopy & Microanalysis 2015 Volume 21, Issue S3, August 2015, pp. 799-800.
This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-EE0007271.

Figure 1
(Invited) Membrane Electrode Assembly for Alkaline Anion Exchange Membrane Fuel Cell
Authors: Yu Hongmei 
Published: February 2020

Anion exchange membrane fuel cell (AEMFC) is expected as a promising power source candidate as it may enables the adoption of non-precious metal catalysts; therfore, it exhibits great advantages over proton exchange membrane fuel cell (PEMFC) using precious metal catalysts . However, AEMFCs are much less understood than PEMFCs. As a key component, the membrane electrode assembly plays an important role in AEMFCs. The electrode fabrication and resulting microstructure largely determinates the performance of AEMFCs.
In this work, the electrode microstructure of a AEMFC was investigated. The ionomer content in catalyst layers as well as the dispersion solvents for catalyst inks have shown a strong impact on the active, ohmic and mass-diffusion polarization losses of a AEMFC. Performance measurements of a single cell, as well as a stack, were implemented to evaluate the feasibility of AEMFC applications. Pt-free AEMFC stack was assembled and tested in DICP.
In addition, a novel cathode architecture is also developed., which uses vertically aligned nanoneedle arrays as an oriented catalyst support for the AEMFC Without ionomer, the oriented catalyst layer shows its potential application in AEMFCs.
Four-in-One Electrode for Micro Polymer Electrolyte Membrane Fuel Cells
Authors: Li Yinshi 
Published: February 2020

The miniaturization of the µPEMFC can be readily achieved by scaling down the size of the cell components, it, however, strongly depends on the development of the micro-scaled tailoring, fabricating and assembling technologies [1, 2]. Therefore, designing a novel architecture that integrates the different components will be a more effective way to miniaturize the cell system. This work presents an efficient strategy by developing a four-in-one electrode, in which the functions of the flow field, backing layer, micro-porous layer, and catalyst layer are brought together. This integrated design facilitates the mass and charge transport as well as extends the three-phase boundary, thereby enabling to miniaturize the cell system while enhance the power output [3, 4]. It has been demonstrated that when applying a pair of the four-in-one electrode (the height, length and width respective 500 µm, 4 mm and 4 mm) to the liquid-feed µPEMFC, the peak power density goes up to 123 mW cm-2 even at room temperature. This four-in-one electrode makes it possible to develop a simple-structure and high-performance liquid-feed µPEMFC for lab-on-a-chip applications.

References

[1] J.P. Esquivel, M. Castellarnau, T. Senn, B. Lochel, J. Samitier, N. Sabat, Lab. Chip, 2012, 12: 74-79.
[2] Y. S. Li, Int. J. Hydrogen Energy, 2016, 41: 3600-3604.
[3] Y.S. Li, J.H. Lv, Y.L. He, J. Electrochem. Soc., 2016, 163: F424-F427.
[4] Y.S. Li, Y.L. He, J. Electrochem. Soc., 2016, 163: F663-F667.
(Invited) The Fuel Cell Solution for Automobile Industry
Authors: Hou Zhongjun , Shi Weiyu , Wang Keyong , Xing Danmin , Liang Dong , Wang Renfang , Ming Pingwen 
Published: February 2020

Proton exchange membrane fuel cell (PEMFC) has been considered as an ideal power source of electric vehicle propulsion due to its high power and energy density, particularly when combined with high pressure hydrogen storage technology. After decades of R&D, the PEMFC technology has been improved to a commercially viable level. In the next five years, the automobile industry in China will invest substantially more efforts on fuel cell vehicles, and Chinese government has launched an attractive subsidy policy towards commercialization of fuel cell vehicles.
Sunrise Power has focused on achieving fuel cell technology targets for automobile industry over fifteen years. Three generations of PEMFC power systems has been developed to enhance the power density, durability, and to reduce the cost.The 1st generation of PEMFC power system was developed for fuel cell vehicle demonstration during “2008 Beijing Olympic Games” and “2010 Shanghai EXPO” in China. And the fuel cell lifetime between 1000~2000 hours was demonstrated. The 2nd generation optimized the system and stack design following a fuel cell failure mode, which was disclosed via the degradation research on the 1st generation fuel cell systems. And it has been validated that the fuel cell lifetime can be improved to about 5000 hours. The 3rd generation eliminated air humidification via the adoption of a water management strategy to achieve higher power density and lower cost. Basing on the research, Sunrise Power has launched fuel cell product portfolio of HyMOD, HyMOD+ and HySYS to support the application of the fuel cell vehicle industry.