bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Lithium-Ion Battery-Capacitor Hybrid Energy Storage Devices
Authors: Zheng Jim P. , Shellikeri Annadanesh , Hagen Mark Andrew , Cao Wanjun 
Published: February 2020

As a new generation of supercapacitor, the Li-ion capacitor (LIC) is an advanced energy storage device which consists of an electric double-layer capacitor (EDLC) cathode and a pre-lithiated anode [1,2], between which the ions shuttle during charge and discharge processes. Because of using pre-lithiated and low surface anode materials, the LIC can be charged to a maximum voltage as high as 4.0 V, which is much higher than of EDLCs and comparable to Li-ion batteries (LIBs); therefore, it allows the LIC and LIB to be assembled in one package as a LIB/LIC hybrid energy storage cell.
We have demonstrated a new hybrid energy storage cell that combines the advantages of both the LIB and the LIC [3], thereby avoiding their inherent defects, while bridging the gap between the high energy densities offered by batteries and the high power densities seen in EDLCs. The energy density and power density of the hybrid cell can be designed to meet the requirements by a reasonable distribution of the ratio between LIB and LIC electrode materials in the internal hybrid cell. For example, we show a hybrid LIC consisting of a Li nickel cobalt manganese oxide (NMC)/activated carbon (AC) composite cathode in combination with an ultra-thin Li film (u-Li) pre-loaded hard carbon anode. Additionally, we show that by utilizing three design approaches: dry composite electrode fabrication method, cathode to anode capacity ratio design, and pre-lithiation method using u-Li, we can demonstrate an energy storage device with excellent cycle life, and that can be tailored by composite ratios within the cathode to fit different applications. Shown here is an in-depth look at various composite material ratios, pre-lithiation calculations and hybrid Li-ion battery-capacitor energy storage device creation based on targeting essential energy-power performance characteristics.
References
[1] W.J. Cao and J.P. Zheng, “Li-ion Capacitors with Carbon Cathode and Hard Carbon/SLMP Anode Electrodes”, J. Power Sources, 213, 180 (2012).
[2] W.J. Cao, J. Shih, J.P. Zheng, and T. Doung, “Development and characterization of Li-ion capacitor pouch cells”, J. Power Sources, 257, 388 (2014).
[3] Zheng, J.-S., Zhang, L., Shellikeri, A., Cao, W., Wu, Q., & Zheng, J. P. (2017). A hybrid electrochemical device based on a synergetic inner combination of Li ion battery and Li ion capacitor for energy storage. Scientific Reports, 7, 41910.
(Invited) Design of Biomolecular Piezoelectric Materials for Energy Generators
Authors: Lee Ju Hyuck 
Published: February 2020

Piezoelectric materials are excellent generators of clean renewable energy because they can convert ubiquitous vibration and mechanical power into electrical energy. Although traditional piezoelectric materials such as lead zirconate titanate (PZT), lithium niobate, gallium nitride, and barium titanate are practical for energy generation, their fabrication frequently requires environmentally harmful components and/or energy processes. Recent studies on environmental friend biomolecular piezoelectric materials such as amino acids, peptides, proteins, and viruses have great attention because they are applicable to bioelectronics and biomedical applications. Compared with inorganic and synthetic counterparts, however, biomolecular piezoelectric materials have not been extensively studied for general piezoelectric applications because the piezoelectric response of the major piezoelectric components (d33, d31, d11) are weak. Furthermore, the difficulty of fabricating unidirectionally polarized biomolecular piezoelectric structures that can efficiently convert mechanical energy into electrical energy has been a major obstacle to the realization of robust piezoelectric energy generators.
In this talk, I will introduce recent research on strategies and methods for synthesizing and controlling large-scale aligned various biomolecule piezoelectric materials. The orientation and polarization directions of these materials were controlled using biomimetic self-assembly process which is low cost and environmentally friend process. Furthermore, the energy generators based on the biomolecular piezoelectric materials were demonstrated.
(Invited) Piezo-Phototronics Effects on the Collective Behavior of Injected Excitons in GaN-Based Multi-Quantum Wells at Threshold
Authors: Li Ding 
Published: February 2020

Realizing Bose-Einstein condensation (BEC) has found intense interest. Up to now extreme conditions like very low temperature and high magnetic field were usually necessary to achieve BEC for low density systems consisting of atoms. Recently, many efforts have been devoted to finding a solid-state system in which BEC can take place. Photoexcited excitons as light-mass bose particles, consisting of bound electron–hole pairs in semiconductors, had triggered intense interest for long time. Excitons as bosons, which can be generated at high density in semiconductor quantum wells, are potential candidates to realize exciton condensation. If their binding energy is higher than kT, which is given for excitons in gallium nitride (GaN) with binding energy of 48 meV, additional confinement in a quantum well (QW) should increase the interaction between excitons and thus offer the chance to observe exciton condensation.
To bring BEC into daily applications, it is highly desirable to realize BEC in a real-world device at room temperature (RT) and free from extreme conditions. Here, we report a simple way to realize boson condensation in a low energy state in GaN-based multi-quantum-well (MQW) laser diodes (LD) at RT. It is revealed by the analysis of abnormal electrical and optical behaviour of GaN-LDs. At threshold, due to the piezo-phototronics effects and the coherent light field, the involved excitons (bosons) in the QW, as dipoles, behave collectively with identical energy and the same direction, which means that they condense into a coherent low energy state. This is confirmed by a redshift of electroluminescence spectra. This quantum effect corresponds to a phase transition in a far-from-equilibrium system, which is an open system exchanging matter and energy with the outside.
The Thermal Characteristics of AlGaN/GaN Hemts with Different Channel Width
Authors: Lin Wei-Chun , Zhong Yi Nan , Tsai Ming-Yan , Ho Wei-Cheng , Yu Yi-Hsuan , Hsin Yue-Ming 
Published: February 2020

In this study, the thermal characteristics of AlGaN/GaN HEMTs with different channel widths were investigated. The thermal characteristics including threshold voltage, maximum transconductance (gm,max), on-state current, and on-resistance were investigated from 30 to 150 °C with the increment of 10°C. All devices have the same source, gate and drain widths, but difference in the channel widths. The channel width (Wchannel) is determined by a current blocking region between the source and drain. Device A is a conventional device with gate width (WG) of 50 mm without the current blocking region. Therefore, the channel width is the same as the gate width. Device B, C, and D have the gate width of 50 mm but different channel widths of 27.5, 25, and 12.5 mm, respectively. The dimension of the channel width was implemented by ion-implantation at the process step of device isolation. All epitaxial layers were grown on Si substrate. All devices were passivated by a 200-nm PECVD SiN without field plates. The devices under test are with a gate-source distance (LGS) of 4-µm, a gate length (LG) of 2-µm, gate width (WG) of 50-µm, and a gate-drain distance (LGD) of 10-µm.
At room temperature, device B, C, and D with smaller channel widths show the improved on-state current density, subthreshold swing, and gm. Device D shows a gm,max of 239 mS/mm compared to the 127 mS/mm of the device A. A significant improvement was observed in gm,max of device D due to the large ratio of WG/Wchannel. A better capability of the gate control is achieved. However, the thermal characteristics show the opposite trend. The measured thermal coefficients of the threshold voltage, gm,max, on-state current, and on-resistance of the device D are 2.1´10-4, -6.7´10-3, -3.4´10-3, and 1.1´10-2 1/°C compared with 1.5´10-5, -1.4´10-3, -2.1´10-3, and 7.2´10-3 1/°C of the device A. The possible reason is due to the current crowding at the corners of the blocking region. A suitable heatsink design or back side via are required to reduce the thermal impact.

Figure 1
Constrained Optimization of Proton Exchange Membrane Fuel Cells Using a Finite Element Approach
Authors: Lamb James , Andrei Petru 
Published: February 2020

Our group has recently proposed a large scale optimization technique for computing the optimum distribution of platinum particles in proton exchange membrane fuel cells (PEMFCs) [1]. The basic idea of the technique was to use the adjoint method to compute the catalyst sensitivity functions and to introduce these functions in a gradient-based algorithm to estimate the optimum catalyst distribution in the catalyst layers [2]. In our previous work, constraints were taken into consideration using the formalism of Lagrange multipliers on the functional space of possible catalyst distributions [3]. Although robust, this approach was restricted to equality constraints and could not be applied to the more general case in which constraints enter as inequalities in this optimization function.
In this work we will present a new optimization method for PEFMCs that includes inequality constraints. The method is still based on the computation of the catalyst sensitivity functions using the adjoint method but allows the optimizer to search for solutions away from the boundaries imposed by the constraints. By using this method, we are able to compute the global optimum platinum distribution inside the catalyst layer. In addition, we extend the method to the calculation of the optimum porosity and Nafion distribution in the gas diffusion and catalyst layers, respectively. Details about the numerical implementation of the method and sample optimization results will be presented and compared to previous results at the meeting.
References
[1] J. Lamb, G. Mixon and P. Andrei, “Adjoint Method for the Optimization of the Catalyst Distribution in Proton Exchange Membrane Fuel Cells”, Journal of the Electrochemical Society, 164, E3232 (2017).
[2] J. Lamb, G. Mixon, and P. Andrei, “Mathematical Optimization of the Spatial Distribution of Platinum Particles in the Catalyst Layer of PEMFCs”, ECS Transactions 2017 77(11): 1179-1196.
[3] J. Lamb and P. Andrei, “Analysis of Sensitivity of PEMFC Parameters to Non-Uniform Platinum Deposition Diagnostics and Characterization Methods”, ECS Transactions 2017 80(8): 291-300.
Understanding Pyrolysis of PGM-Free Electrocatalysts with X-Ray Computed Tomography
Authors: Huang Ying , Shum Andrew , Rezaei Talarposhti Morteza , Asset Tristan , Parkinson Dilworth Y. , Barnard Harold , Atanassov Plamen , Zenyuk Iryna V. 
Published: February 2020

Atomically dispersed Fe-N-C electrocatalyst is the emerging advanced type of PGM-free catalyst. Its activity arises from a multitude of active sites, often viewed as co-catalytic (bifunctional sites), such as atomically-dispersed iron in nitrogen coordination (FeNx) and pyridinic and pyrrolic nitrogen moieties in graphene structures. The synthesis of Fe-N-C electrocatalysts involves a pyrolysis step, for which physical and chemical transformations are not well understood. Various ramps and temperature holds are currently used to evaporate precursors and solvents and to achieve the electrocatalyst’s high electric conductivity. An additional pyrolysis step, termed second pyrolysis, is sometimes used. Recipes exist with the pyrolysis of various precursors to arrive at catalyst that contains a high content of nitrogen. Here, Fe(NO3)3 .9 H2O and an aromatic amine charge-transfer organic salt, nicarbazin, was used. Custom pyrolysis furnace built by the Advanced Light Source’s (ALS) 8.3.2 beamline scientists was used that was capable of having gas circulation, high temperature and, at the same time, a rotating stage for x-ray computed tomography (CT) imaging. After ball-milling, the sample was placed on a ceramic stage of the vertical furnace with a circulating gas mixture of nitrogen and 7 % hydrogen. The catalyst was inserted at 525°C and then furnace temperature was increased; first to 900°C in 12 min (31.25 °C/min) and then to 975°C in 8 min (9.375 °C/min). After a 45 min hold time, the catalyst was removed from the furnace. Seven X-ray CT scans were performed during this pyrolysis process. This is the first study to use micro X-ray CT to observe the morphological changes of a catalyst powder during a pyrolysis process. Figure 1 shows the schematic of the stage, the quartz tube used to seal the gases and the ceramic stage for the catalyst placement. A photograph of our mounted catalyst within the pyrolysis chamber on the rotating stage is shown by Figure 1b and a temperature profile by Figure 1c. We have found that most of the changes in the catalyst morphology happen during the temperature ramp to 975oC and during cool down. The temperature hold at 975°C did not result in significant powder morphological changes. A follow-up study was conducted where the temperature ramp was studied in more detail with X-ray CT scans taken every 100°C. Furthermore, a second pyrolysis study was conducted where morphological changes were not observed.
Figure 1. a) Schematic of pyrolysis stage and gases circulation, b) a photograph of our sample mounted within the pyrolysis chamber at 8.3.2 ALS during imaging, c) the temperature ramp during pyrolysis and d) the evolution of catalyst morphology during temperature ramp.

Figure 1
Effect of Cathode Catalyst Layer Structure on the Performance of PEFC
Authors: Heggo Dalia , Ma Yulei , Balci Beste , Kageyama Miho , Yamaguchi Kazuhiro , Kawase Motoaki 
Published: February 2020

One of the routes to promote PEFC commercialization is to reduce its manufacture cost. Platinum represents more than 50% of PEFC cost. Therefore, two targets can be considered; reduction of platinum loading (g/cm2) at cathode, and increase specific catalytic activity towards reaction (mA/cm2
pt).

On the other hand, the effectiveness factor has an inherent relation with current density and mass transfer of reactants (oxygen and proton), which are existing simultaneously. For investigating cathode behavior, two dimensionless moduli, representing diffusion limitations due to oxygen and proton mass transfer resistances, have been proposed 1.
To estimate mass transport resistances, effectiveness factor and intrinsic reaction rate constant, experiments were carried out by varying cathode catalyst layer (CCL) structure on a membrane electrode assembly (MEA). The MEA, fabricated by decal transfer method, consisted of a Nafion membrane (NR-212, 50 μm) with Pt/C weight ratio of 0.3, 0.4 and 0.5 in 10 μm CCL. The ionomer (I)/C ratio was 1. The CCL was prepared by two methods. The first, Pt particles were supported on carbon (Ketjen black) relevant to the required Pt/C ratio (Standard catalyst preparation). The second, lower Pt/C ratios were manipulated by adding carbon black (CB) to a prepared catalyst mixture contained 50% Pt/C where Pt loading was 0.3 mg/cm2 (CB dilution method). The IR corrected voltage (electromotive force) was calculated by measuring the polarization curves and membrane resistance using an electrochemical measurement system. The impedance spectra were measured in a range of frequency from 10 mHz to 100 kHz.
The analysis of the results using our dimensionless moduli approach may support having deeper insight that could accelerate the development of PEFC.
Reference:

M. Kawase et al., AIChE J., 63, 249–256 (2017) http://doi.wiley.com/10.1002/aic.15545.

Figure 1
New Hydrogen-PEMFC Portable System and Applications
Authors: Ferreira-Aparicio Paloma , Molinero Antonio , Oller Juan Carlos , Barcala José Miguel , Santamaría Santiago , Serrano José Luis , Chaparro Antonio M 
Published: February 2020

Hydrogen portable applications may overcome shortcomings of batteries especially concerning autonomy and safety. On the other hand, energy systems based on fuel cells and hydrogen are more complex and voluminous, compared with battery systems where the energy storage and power consumption are integrated in the same device. It is for this reason that fuel cells for portable applications require new architectures and working conditions that allow minimizing system requirements without the loss of efficiency.
This communication will show new developments for hydrogen portable applications, concerning cell configuration, stacks, and systems, in order to improve portability and efficiency and decreasing fuel cell system consumption. The cells are able to work under full passive conditions, without the aid of fans and purging valves. The stack configuration allows easy integration, repairing, and dismantling of single cells without affecting the other cells. Power generation systems have been developed based on boost converter electronic and the integration of supercapacitors to provide short events of high power demands to the applications. Results of system behavior and response in real applications will be shown.
Acknowledgements.
This work was supported by the Ministerio de Economía y Competitividad of Spain, and Fondo Europeo de Desarrollo Regional (FEDER), Project E-LIG-E, ENE2015-70417-P (MINECO/FEDER).

Figure 1
Highly Stable Polybenzimidazole (PBI) Grafted graphene As Catalyst for Polymer Electrolyte Membrane Fuel Cells
Authors: Li Chenzhao , Liu Yadong , Yu Kang , Xie Jian , Ferreira Paulo Jorge 
Published: February 2020

Graphene is a single atomic-tick graphite layer. The carbon atoms in the graphene plane are saturated due to the bonding structure: each has 3 covalent bonds with three neighboring carbon atoms in the graphene plane, the lone px

e-
form a long range conjugated system, a big π bond. This leads to some unique properties: excellent electric conductivity and chemical stability, which are critically needed for catalyst supports in polymer electrolyte membrane fuel cells (PEMFCs).[1] The catalyst support stability plays a significant role in determining the overall durability of PEMFC systems when PEMFCS are subjected to very high potential cycling , for example, from 1 V to 1.5 V. However, there are three major obstacles for graphene supported Pt based catalysts in PEMFCs: 1) there are limited bonding sites for catalyst landing on the graphene basal plane, which lead to migration/aggregations of Pt nanoparticles when subjected to harsh accelerated durability tests (ADTs); 2) it is very difficult for Nafion ionomer particles and graphene based catalyst mixing together to form a uniform catalyst ink, which results in the poor catalyst/ionomer interface. 3) For MEA preparation using ink spraying method, when ink is dried, the π-π interaction makes 2D graphene sheets easily restacking back to graphite structure, which could severely block the mass transport of gas and water, leading to poor MEA performance at high current.
To overcome these barriers, we propose a novel approach to transfer the 2D graphene sheets into 3D composite with sufficient channels and pores for facile mass transport. This is realized by developing the highly stable hierarchical polybenzimidazole (PBI) -grafted nano-graphene supported Pt catalysts for PEMFCs and applying spacers during ink formulation. Nano- graphene, comparing with normal graphene, has smaller dimensions as the catalyst supports, which makes the pores/channels between graphene sheets much shorter, facilitating the mass transport. It is expected to see some extra voltage gains at the high current density.
In order to construct appropriate pore structures in the catalyst layers, spacers are introduced. However, although the initial performance somehow increases with such modification, yet the support durability remains same and to some extents, decrease little bit. In this case, the hypothesis raised that during durability test, the spacers themselves are corroded and graphene sheets are restacked. To overcome this barrier, we apply more stable spacer that match the durability of graphene. Nano-silicon powder is very stable during voltage scan between 1.0V to 1.5V but is not conductible. To remedy this drawback, we coat highly graphitized carbon over its surface, which gives very promising durability and conductivity for overall MEA electrode.
[1]. Geim, A. K.; Novoselov, K. S. Nat. Mater. 2007, 6, 183
One-Step Synthesis of Manganese Doped Single Atom Catalysts for Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells
Authors: Stracensky Thomas Stephen , Ding Shuo , Lattimer Judith , Mukerjee Sanjeev , Xu Hui 
Published: February 2020

Current commercial catalysts for polymer electrolyte membrane fuel cells (PEMFCs) require platinum group metal (PGM) catalysts that lead to high costs, thus preventing viable commercialization of PEM fuel cells. Many investigations into PGM-free catalysts have led to the identification of single metal atom sites coordinated with 4 nitrogens as being highly active. One of the best performing metal centers in the acidic environment of the PEMFC is Iron (Fe). Highly active iron-based catalysts have been synthesized easily via a one-step method of doping Iron into a ZIF-8 framework; however, there have been membrane degradation concerns due to the Fenton reaction products that are generated by Fe. Manganese (Mn) has recently been proposed as a potential metal center for the highly active metal-N4 catalyst site as theory predicts that it will have good activity and increased stability1 .
The best performing Mn-based catalysts have been synthesized from a Mn doped ZIF-8 structure, but due to the high oxophilicity of Mn and difficulty in incorporating Mn into the ZIF structure, a laborious Mn catalyst synthesis route has been adopted, which requires acid leaching, secondary doping, and multiple pyrolysis steps2. This causes problems in scaling up the synthesis and limits the active site density when compared to the Fe catalyst.
We aim to use highly reactive Mn metal precursors in an air-free environment to incorporate Mn into the metal sites of ZIF. High temperature pyrolysis (1100°C) leads to manganese catalyst synthesis in one step.
We show that using a highly active manganese borohydride precursor allows for the formation of a metal organic framework (MOF) when combined with 2-methylimidazole, which can subsequently be pyrolyzed to form the target catalyst. Using zinc borohydride as a secondary metal source we can also form bimetallic MOF structures with increased thermal stability and varied Mn loading. With this strategy Mn can be incorporated directly into the metal MOF sites with a wide range of Mn loading. The utilization of an air-free environment prevents metal oxide formation thus giving a facile one step synthesis of a manganese-based catalyst.
(1) Liu, K.; Qiao, Z.; Hwang, S.; Liu, Z.; Zhang, H.; Su, D.; Xu, H.; Wu, G.; Wang, G. Mn- and N- Doped Carbon as Promising Catalysts for Oxygen Reduction Reaction_ Theoretical Prediction and Experimental Validation. 2018.
(2) Li, J.; Chen, M.; Cullen, D. A.; Hwang, S.; Wang, M.; Li, B.; Liu, K.; Karakalos, S.; Lucero, M.; Zhang, H.; et al. Atomically Dispersed Manganese Catalysts for Oxygen Reduction in Proton-Exchange Membrane Fuel Cells. Nat. Catal.
2018, 1 (12), 935–945.