bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Novel Implantation Processing and Characterization for Scalable GaN Power Devices
Authors: Goorsky Mark S. , Bai Tingyu , Li Chao , Tadjer Marko J. , Hobart Karl D , Anderson Travis J , Hite Jennifer K , Feigelson Boris 
Published: February 2020

Novel ion implantation processing has been introduced to enable p-type doping for high performance vertical GaN p-n power devices. Multicycle Rapid Thermal Annealing (MRTA) leads to state-of the-art p-type doping (> 8% dopant ionization); high n-type doping can also be achieved. The implantation process is also compatible with a tapered implanted junction terminal extension approach to achieve effective edge termination necessary to provide breakdown voltages over 90% of the theoretical maximum value at minimal cost and processing complexity.
MRTA, with ambient control (N2 ambient at 200 psi), pulsed annealing up to ~1400 °C, and an appropriate dielectric encapsulant, is utilized to further improve activation efficiency and, ultimately, p-n junction performance through selective ion implantation and processing optimization. Here, the focus is on MRTA activation of Mg+ implantation, with comparison to the potential effectiveness of other p-type dopants, to assess the impact of the crystalline nature of the substrate and to optimize the encapsulant mask, in order to promote the highest dopant activation. This fundamental study of the role of defects in material produced by GaN epitaxial deposition is expected to lead to a pathway to high activation efficiency through a mechanistic understanding of the relationship between processing methods and performance. The critical link between defects and implant activation will be discussed through the use of novel structural materials characterization techniques as well as standard electrical and optical techniques. Electron microscopy defect analysis, determining the role of implanted and annealed defects, and providing localized strain measurements helps assess defect evolution as a function of implant and annealing parameters. X-ray based reciprocal space mapping as a function of the implant and subsequent annealing will be shown to correlate strain and defect formation with dopant activation in order to parameterize the MRTA process non-destructively. This information leads to the production of p-n junction devices that are scalable, provide high surge currents, and high ideality factors. Understanding point defect concentrations, dislocation types and concentrations, and residual stress will lead to effective p-type dopant activation and high device performance.
Oxygen Transport Effects of Cobalt Cation Contamination of Ionomer Thin Films in Proton Exchange Membrane Fuel Cells
Authors: Braaten Jonathan , Kongkanand Anusorn , Litster Shawn 
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) are a promising automotive energy conversion technology for reducing the dependence on petroleum and reducing greenhouse gas emissions. However, the high cost of the platinum (Pt) electrocatalyst responsible for increasing the rate of the oxygen (O2) reduction reaction (ORR) in the cathode is one of the primary inhibitors to this technology’s mass market penetration. In order for PEMFCs to become cost competitive with internal combustion engine technologies, the electrocatalyst cost must be significantly reduced. To address this issue, the use of Pt alloys such as Pt3Co has been explored. Alloys such as Pt3Co have been shown to have higher activities than pure Pt electrocatalysts,(1) reducing the mass of the expensive Pt. However, the utilization of Pt3Co poses contamination risks to the ionomers used in PEMFCs due to cobalt’s (Co) propensity to dissolve out of the catalyst, migrate to the ionomer, and replace protons on the sulfonic acid sites(1). Cai et al.(2) demonstrated the effects of this risk through the testing of membrane electrode assemblies (MEAs) containing Co doped ionomers, which showed a decrease in proton conductivity through the ionomer. In addition, Kongkanand et al.(3) have shown that voltage losses at high current densities for low-Pt loaded electrodes can be attributed to localized O2 transport resistances in the thin films of ionomer covering the electrocatalyst surface. Thus, the effects of dissolved Co on the local O2 transport through these thin films of ionomer are of particular interest.

The purpose of this work is to experimentally characterize the effects of Co contamination on the localized O2 transport properties of ionomer thin films. To study these effects, we modified an existing fuel cell to allow for the testing of gas (O2) transport through ionomer thin films in a well-controlled environment, similar to the setup used by Liu et al.(4) The setup allows for the films’ transport resistance to be measured under non-polarized (uniform Co distribution) and interface free conditions, in order to isolate the effect of the Co contamination. In addition, the setup allows for the control of the ionomer sample’s temperature and relative humidity, to evaluate the effects of each on the O2 transport resistance of the doped thin films. To test the effects of differing levels of Co cation contamination during PEMFC operation, we take O2 transport resistance measurements for various amounts of controlled Co ion doping. Our preliminary results have indicated significant increases in O2 transport resistances for high Co contamination levels, consistent with our hypotheses derived from the results mentioned above(2, 3).

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
Visualization of Liquid Water Distribution at Interfaces of PEFC by Using Parallel-Beam Soft X-ray Radiography
Authors: Naito Hiroshi , Jao Ting-Chu , Yoshida Toshihiko , Sasabe Takashi , Kawamura Katsuyuki , Hirai Shuichiro 
Published: February 2020

Because of increasing expectation of the use of PEFC, further improvement of the performance is still demanded. Since the liquid water generation and its accumulation inside the PEFC is one of the most influential phenomena for the electric generation performances, it is required to obtain knowledge about the actual liquid water distribution inside the PEFC and its generation/drainage process in order to promote the efficiency of the PEFC. Particularly, the detailed liquid water behavior at the interfaces has not been provided in spite of its large impact on the liquid water drainage performances. By using soft X-ray radiography, our laboratory has reported liquid water distribution inside the PEFC. In principle, however, the conventional cone beam type X-ray used so far has difficulty to capture the interfaces because of the widening effect of the X-ray beam. This problem can be solved by parallel type X-ray beam. In this study, we introduce a parallel beam type X-ray microscope to improve the accuracy of the interface measurement. We especially focus on the liquid water distribution at the GDL/MPL/CL/membrane interfaces.
In this study, in-plane measurement is performed to obtain two-dimensional visualization having rib/channel configuration. The visualization result operated at 30℃ cell temperature, 80% relative humidity and 0.6A/cm2 current density, is shown in fig.1. In the wide region on the cathode rib, accumulation of liquid water is observed same as reported in some other previous studies. Also, it is clearly shown that, in the CL/MPL interface of cathode side, film-like water distribution is created due to capillary pressure gap. In the presentation we will also focus on the generation/drainage process of the liquid water including intermittent behavior on the interfaces.
This work is supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Figure 1
The ARPA-E Ionics Program: Advancing Anion Exchange Membranes
Authors: Albertus Paul S. , Babinec Susan J. , Pouy Mark J. 
Published: February 2020

In 2016 ARPA-E launched the IONICS (Integration and Optimization of Novel Ion-Conducing Solids) program, motivated by the enabling role of separator technology and the remaining performance and cost gaps across multiple types of electrochemical devices. The 16 teams in the IONICS program are focused on developing breakthrough separators that would be broadly enabling in different areas of electrochemical technology, and also amenable to cost effective manufacturing. The projects include both polymer and inorganic ion conducting separators that enable electrode chemistries that have been previously unsuccessful in practical devices. Project teams are focused on overcoming property tradeoffs to achieve a full set of required attributes, including conductivity, selectivity, stability, mechanical properties, manufacturability, cost, and others. This contrasts with a common approach of optimizing a single variable at the expense of others. The IONICS focus is on solids rather than liquids, due to inherent advantages in selectivity and mechanical properties offered by solids.
The IONICS program is focused on three areas: (1) Li+ conductors that enable the cycling of the lithium metal electrode at conditions required for high-energy cells, (2) highly selective polymer separators for flow batteries, and (3) anion-conducting polymer separators for use in alkaline fuel cells, electrolyzers, and other electrochemical devices. This talk will focus on area (3), where the potential benefits of the alkaline environment include the reduction/elimination of platinum-group metal catalysts for both hydrogen and oxygen electrodes, and the ability to use lower cost, uncoated, stainless steel plates. The polymer attributes pursued in the program include extended stability (1,000 h with negligible degradation) in alkaline conditions at a temperature of 80°C or higher, low area-specific ionic resistance (<=0.04 ohm-cm2 in liquid form), limited swelling (<50%), and low cost (<=20 $/m2). Additionally, fuel cell applications require the membrane to retain high conductivity under air exposure and avoid degradation during humidity cycling, while electrolysis applications require it to withstand a differential pressure of tens of bar. A key limitation for the development of improved membranes in this growing field is the lack of specific, consistent test conditions, which makes it difficult to easily identify the most promising membranes. This talk will outline the test conditions developed for the IONICS program teams, which we hope will be used by other research groups to advance progress in this important field.
Co,N-Codoped Mesoporous Carbon As Efficient Bifunctional Catalysts for Oxygen Reduction and Hydrogen Evolution Reaction
Authors: Liu Xiaojun , Zou Shouzhong 
Published: February 2020

Pt-based catalysts have been extensively studied as polymer electrolyte fuel cell catalysts and hydrogen evolution reaction (HER) catalysts. However, the low abundance and high cost of these materials preclude their large-scale commercial applications. Alternative more sustainable catalysts are therefore needed. Various carbon-based materials have been demonstrated to have high oxygen reduction reaction activity especially in the alkaline media. In this work, we report a simple silica template approach to form porous carbon codoped with nitrogen and cobalt. The obtained porous carbon exhibited not only excellent electrocatalytic activities for ORR, which compare favorably with that of commercial Pt/C (20 wt%), but also superior durability and methanol tolerance. The porous carbon also possess superior performance for HER in acidic media, showing a low onset potential of only -0.04 V vs RHE, a Tafel slop of 57.4 mV dec-1, a current density of 10 mA cm-2 at -0.106 V vs RHE and remarkable durability. Thus, the Co, N-doped carbon holds great promise as bifunctional catalysts for regenerative fuel cells.
Development of Carbon-Free Electrocatalysts for Water Electrolysis
Authors: Muto Marika , Sasaki Kazunari , Hayashi Akari 
Published: February 2020

Introduction Hydrogen production from water electrolysis and further electricity generation through fuel cells have been focused on as one of the efficient uses of renewable energy. Regarding to water electrolysis, the PEM type water electrolyzer is attractive in terms of reduced ohmic resistance and also a similar assembly to well-developed PEFCs. On the other hand, the relatively low active surface area of anode electrocatalysts is a problem since carbon supports are not usable in order to disperse small catalyst particles under the high potential condition over 1.5 V. So far, our group has been working on mesoporous materials for PEFCs. We have found that mesoporous materials can keep those porous structures even after being built into the device, and then, the porous structure can improve the mass transfer within catalyst layers. Based on the similar idea used in our PEFC studies, we propose development of carbon-free mesoporous metal catalysts with high active surface area to increase the efficiency of water electrolyzer. In this study, mesoporous Pt and Ir materials were particularly developed and further evaluated as anode electrocatalysts.

Experimental method

Similar to the synthesis of mesoporous carbon,1 a surfactant, Pluronic F127, was used as a template to form a porous structure. Pt(acac)2 and Ir(acac)3 were used as metal precursors. After mixing the surfactant and metal precursors, the resultant complex was slowly heated up in N2or Air atmosphere to make the mesoporous structure. After the basic material characterizations, their electrochemical measurements were performed using a common half-cell setup in the solution. Oxygen evolution reaction (OER) activity was evaluated as anode electrocatalysts. The durability against high potential like 1.8 V was also analyzed.

Results and discussion

The resulting Pt material was confirmed to have a porous structure constructed by aggregation of Pt nanoparticles as shown in Figure 1. Based on the nitrogen sorption measurement, the randomly oriented porous structure was also confirmed, and the pore diameter was found mostly smaller than 100 nm. With this porous Pt material, OER activity was evaluated and compared with a standard Pt/KB electrocatalyst, TEC10E50E. As shown in Figure 2, the initial activity resulted in the same even though ECSA was six times higher for Pt/KB. Then, the durability of porous Pt and Pt/KB was examined by applying continuous high potential of 1.8 V. Dot lines in Figure 2 shows the OER activity after 10 minutes of holding at 1.8 V．As expected, Pt/KB lost most of OER activity owing to carbon corrosion. Consequently, carbon-free porous Pt electrocatalyst was successfully prepared and its high activity and durability was confirmed. Similarly, porous Ir electrocatalyst is prepared and its OER activity will be discussed.
Reference
(1) A. Hayashi, et al., Electrochim. Acta,
53, 6117-6125 (2008).

Figure 1
Two-Dimensional Iridium-Nickel-Oxide Nanoframes for High Activity Oxygen Evolution Electrocatalysts
Authors: Rhodes Christopher , Godinez-Salomon Fernando , Albiter Luis 
Published: February 2020

Oxygen evolution electrocatalysts with high activity and stability are needed for proton-exchange membrane (PEM) electrolyzers. Iridium oxide (IrOx) has been shown to exhibit both high activity and stability for the oxygen evolution reaction (OER) under acidic conditions. Based on the high cost and limited supply of IrOx, approaches that increase the activity of Ir-based OER catalysts are of significant interest. Recent work has shown that incorporation of Ni within the IrOx structure increases the OER activity.1 Further, the activity of IrOx has been shown to depend on specific surface structures (i.e. edges, corners and facets).2 As an approach to provide high activity OER catalysts, we investigated a unique self-supported IrNixOy two-dimensional (2D) nanoframe structure that allows the combination of (i) incorporation of a non-noble transition metal within the structure to tune the surface atomic and electronic structure, (ii) expression of specific facets and edges, and (iii) an interconnected, carbon-free three-dimensional matrix that allows molecular accessibility. The IrNixOy 2D nanoframes were synthesized by using nickel hydroxide/oxide nanosheets that were decorated with Ir and then treated under controlled temperature/atmosphere treatments to facilitate Ir-Ni interaction. The development of IrNixOy 2D nanoframes extends our group’s recent work on bimetallic Pt-Ni 2D nanoframes which were shown to exhibit high stabilities and activities for the oxygen reduction reaction.3 The 2D nanoframe structure provides an architecture that expresses highly catalytically active surfaces within an interconnected solid and pore network that faciliates molecular access to the reactive surface. The structure of the IrNixOy 2D nanoframes was determined using X-ray diffraction, scanning transmission microscopy, and scanning transmission electron microscopy. Oxygen evolution activities and stabilities were determined using rotating ring disk electrode configuration and will be presented. The ability to combine highly catalytically active surfaces within a 3D nanoarchitecture provides the opportunity to design OER catalysts with improved activity and stability.

References

1. Sen, F. G.; Kinaci, A.; Narayanan, B.; Gray, S. K.; Davis, M. J.; Sankaranarayanan, S.; Chan, M. K. Y. J. Mater. Chem. A
2015,
3, 18970-18982.
2. Reier, T.; Pawolek, Z.; Cherevko, S.; Bruns, M.; Jones, T.; Teschner, D.; Selve, S.; Bergmann, A.; Nong, H. N.; Schlogl, R.; Mayrhofer, K. J. J.; Strasser, P. J. Am. Chem. Soc. 2015, 137, 13031-13040.
3. Godínez-Salomón, F.; Mendoza-Cruz, R; Arellano-Jimenez, M.J., Jose-Yacaman, M.; Rhodes, C.P. (manuscript submitted).
(Invited Plenary) U.S. Department of Energy Hydrogen and Fuel Cell Activities: Progress and Opportunities
Authors: Satyapal Sunita , Miller Eric L. , Papageorgeorgopoulos Dimitrios , Stetson Ned T 
Published: February 2020

The fuel cell industry is poised for significant expansion—with more than 830 patents issued in 2015, second in the clean energy sector only to solar. Global shipments were at 60,000 units worldwide in 2015 with an annual growth of roughly 30 percent every year since 2010, and annual revenues have exceeded $2 million. After decades of research and development (R&D), fuel cell electric vehicles using hydrogen are now commercially available. They achieve significantly higher efficiencies than combustion engines, offering zero-petroleum and zero-emissions driving options with performance meeting consumer expectations – over 360 mile driving range, a few minutes to refuel, and the high torque and quiet characteristics of all-electric platforms. Such characteristics also enable a number of other applications, such as stationary or backup power, auxiliary power, underwater and aircraft systems, trucks, rail, soldier portable power, and remote surveillance systems.
This plenary presentation will provide an overview of the U.S. Department of Energy (DOE) hydrogen and fuel cell activities with a focus on transportation and early market applications, highlighting key progress as well as opportunities. Recent efforts include DOE’s national lab-led consortia, offering state-of-the-art multi-lab core capabilities and leveraging university and industry partners to accelerate materials breakthroughs and innovations in three key areas: ElectroCat, for platinum group metal-free catalysts, HydroGen for advanced water-splitting, and HyMARC for hydrogen storage materials research. A summary of the H2@Scale concept will be provided which lays a framework for the potential wide-scale production and utilization of hydrogen to address key issues such as grid resiliency, energy security, and cross-sectoral emissions reductions. In addition to an overview of current status in commercial developments, the focus will be on key challenges requiring transformational early stage applied research and development. Examples include catalysts, membranes, electrode structures, as well as electrolysis and other advanced water-splitting approaches. Low cost and reliable hydrogen delivery technologies including high efficiency liquefaction, advanced compression such as electrochemical compression, and advanced dispensing technologies will also require R&D relevant to the electrochemistry, chemistry, and engineering research community.
Operando and in Situ Diffraction Investigation of Lithium-Ion Batteries: What Have We Learnt over the Years and Where Are We Heading?
Authors: Sharma Neeraj 
Published: February 2020

A large proportion of the function of batteries arises from the electrodes, and these are in turn mediated by the atomic-scale perturbations or changes in the crystal structure during an electrochemical process (e.g. battery use). A range of researchers have applied operando and in situ diffraction to probe electrode crystal structure evolution during electrochemical processes inside fully functioning batteries. This allows the direct correlation of structural, electrochemical and external parameters, e.g. atomic site occupancies, applied current and temperature, which provides a relatively holistic picture of electrode function.
This talk is divided into two parts, the first delving into the history of operando/in situ diffraction based techniques used to study lithium-ion batteries, encompassing X-ray, neutron and electron diffraction. I will highlight selected developments, recent breakthroughs, and key considerations required for carrying out these studies, including but not limited to cell design and choice of instrument. The second part of the talk will showcase our recent work in this space, trying to push the boundaries of these experiments. Here we are exploring aspects such as battery types with a range of form factors, i.e., thin-film to large format, the influence of temperature whilst performing in situ experiments, long term in situ experiments and particularly pertinent to applications the high-current rate behaviour of electrodes and their relationship to structural evolution or stability.
The presentation will provide a critical snapshot of how operando and in situ diffraction methods ar contributing to the development of lithium-ion batteries.