bluuebunny/crossref_metadata_2025 huggingface dataset:
Dual Sensing By Simple Heteroditopic Salt Receptors Containing an Anthraquinone Unit
Authors: Romański Jan , Karbarz Marcin
Published: February 2020

We synthesized simple ion pair receptors consisting of a crown ether cation binding site and an anthraquinone supported thiourea anion binding domain and studied their anion, cation and salt binding properties using spectroscopic, spectrophotometric and electrochemical measurements in acetonitrille solution. Apart from carboxylate anions, which cause deprotonation all the anions tested were found to associate with receptors more strongly in the presence of sodium cations, whereas in the presence of potassium or ammonium cation the anion binding strength was greatly diminished. A homotopic anion receptor lacking a crown ether unit, was unable to bind sodium salt more strongly than tetrabutylammonium salts. Solution and solid state X-ray measurements revealed that strong sodium coordination with the cation binding domain is responsible for the salt binding enhancement. Electrochemical measurements showed that the addition of anions to the ditopic ion pair receptors pretreated with sodium cations resulted in greater changes in reduction potentials compared to the addition of anions to receptors in the absence of Na+.

Karbarz, M.; Romanski, J. Inorg. Chem.
2016, 55, 3616-3623.

Figure 1
Real-Time Monitoring of Bacterial Metabolites By Scanning Electrochemical Microscopy (SECM)
Authors: Joshi Vrushali S , Kreth Jens , Koley Dipankar
Published: February 2020

Scanning Electrochemical Microscopy (SECM) is used to study the local chemical environment above live bacterial biofilms such as S. gordonii (Sg), S. mutans (Sm) etc. In this study, we report the development of a Pt decorated carbon nanotubes (CNTs) based dual SECM probe to detect low micro-molar range hydrogen peroxide (H2O2) produced by the live bacterial biofilm. This sensor showed sensitivity 2.2 ± 5 mA cm-2 mM-1 with low detection limit of 0.5 µM. Our results indicate that the Sg produced 65-70 μM H2O2 within 30 min in presence of 1 mM glucose in artificial saliva solution (pH 7.2) at 37°C. In addition, we have also developed a unique solid state carbon based potentiometric pH sensor and used as a SECM probe to map the pH change at high spatial resolution above the Sg biofilm. The sensor showed Nernstian response with slope of 58±4 and very fast response time of 5s. The pH mapping above the biofilm showed that pH above the biofilm dropped by one pH unit within 30 min only in 6 pH artificial saliva with 30 mM sucrose at 37°C. Recent developments about the real-time metabolic exchange between two bacterial species (Sg and Sm) in terms of peroxide and pH will be presented in the conference.

Figure 1
Ion Selective Microelectrodes and Scanning Electrochemical Microscopy to Study Dental Materials
Authors: Ummadi Jyothir Ganesh , Downs Corey , Koley Dipankar
Published: February 2020

Solid-state ion-selective microelectrodes have an inherent advantage of having very fast response time and are used as probes for scanning electrochemical microscope (SECM). New dual function calcium ion selective microelectrode (Ca2+-ISME) and pH-ISME were developed and used as a SECM probes in this study to quantitatively map the chemical microenvironment produced by, bioactive glass (BAG). The carbon powder based Ca2+-ISME and the ployaniline deposited pH-ISME showed broad linear response range with Nernstian slopes. The selectivity coefficients of this Ca2+-ISME were found to be log KCa
2+
,A  = -5.5, -6.7, and -6.1  for Mg2+, Na+, and K+, respectively. The Ca2+-ISME had a tip diameter of 25 µm and the inclusion of carbon powder made it redox sensitive. The amperometric function of the sensor was used to fix the tip-substrate distance by using approach curve technique with the SECM. The SECM experiments with the Ca2+-ISME showed that the BAG releases calcium ions in acidic conditions and neutralize the pH in the process. This was an important finding because there was no previous characterization of the 3D chemical environment at the surface of the BAG. The sensors were also used to characterize the dental materials with BAG incorporated into the resin. Such studies can be helpful to characterize novel dental materials that can be commercialized.

Figure 1
(Keynote) 3D Gel Printer for Soft and Wet Matter Engineering and Gel MEMS
Authors: Furukawa Hidemitsu
Published: February 2020

Based on the world-first 3D gel printing technology, we aim to develop 3D gel printing system to realize free-shape design of soft and wet materials and start a new research field of “Gel MEMS”. By virtue of the 3D gel printing system, we can use 3D high-performance gels materials and realize both designed 3D shape and designed function. At the same time, analysis technology with scanning microscopic light scattering will be immediately used to guarantee the quality of manufactured gels. We believe these approaches will contribute to extend the fields of medical and healthcare applications on the Gel MEMS.
Magnetolastic Smart Tags Using Electroformed Cobalt Iron Boron
Authors: Langlois Eric Donald , Pillars Jamin Ryan , Monson Todd , Arrington Christian L. , Finnegan Patrick , Thorpe Adam , St. John Christopher R.
Published: February 2020

Microfabricated magnetoelastic resonators forming the basis for a new, passive, wireless tagging technology platform have been developed. These magnetoelastic tags operate on the principle of Joule magnetostriction (i.e., a large change in material shape induced by an applied AC magnetic field) to produce magnetic signals and are an alternative technology to existing inductive RF tags. Lithographically patterned and electrochemically deposited (ECD) cobalt iron boron (CoFeB) alloy films are used to create the longitudinal mode magnetoelastic resonators. Due to the greater thickness and low-stress nature of electrodeposited films, these resonators can be released like other MEMS devices via a sacrificial layer to form free-standing structures. This batch fabrication technique also allows for multiple resonators of varying lengths and magnetic bias angles resulting in a multi-frequency signal that becomes the tag identity. Hysteresis curves to measure fundamental material magnetic properties that affect tag performance such as magnetic saturation, coercivity, and susceptibility were measured. Process flows for microfabricating resonators along with resonator design, modeling and characterization results will be presented. Future design concepts for tags with environmental sensing functions using this novel material set will be briefly discussed.
Yb,Er-Doped CeO2 Nanotubes for Photoconversion-Ehanced Dye-Sensitized Solar Cells
Authors: Diao Guowang , Zhao Rongfang
Published: February 2020

Abstract: CeO2 doped with trivalent lanthanide ions(Ln3+) that possess intra 4f electronic transitions is a research focus owing to their fascinating optical properties and their significant application in optoelectronic devices[1].The dye-sensitized solar cells(DSSCs) as a promising third generation photovoltaic device have received a great deal of attention since its introduction in 1991 due to its low cost, easy production, and relatively high efficiency. It has recently exhibited an efficiency of 12.3%[2]. Cognitional DSSCs photoanode are comprised of a mesoporous network TiO2 nanoparticles which N719-dye molecules are absorded for light harvesting. We aimed to structure a new type complex photoanode with Yb,Er-doped CeO2 nanotubes(CeO2:Yb,Er NTs). Yb,Er-doped CeO2 nanotubes, synthesized using Ag nanowires as a hard template(as shown in Fig. A and B), were investigated to determine theirs photovoltaic properties in an effort to enhance the power conversion efficiency of dye-sensitized solar cells(DSSCs). Compare with pristine TiO2 photoanode, the DSSCs based CeO2:Yb,Er nanotubes exhibited a power conversion efficiency(η) of 8.67%, an increase of 34%, and incident photo-to-electric conversion efficiency(IPCE) of 92.96%, an increase of 48.83%,as can be seen from Fig. C and D. Energy band matching is formed at the interface of TiO2 layers and CeO2:Yb,Er nanotubes, thereby leading to decrease of electron-hole recombination[3].

References

Z. L. Wang, G. R. Li, Y. N. Ou, Z. P. Feng, D. L. Qu and Y. X. Tong, J. Phys. Chem. C, 2011, 115, 351-356.

A. Y. Pang, X. Sun, H. C. Ruan, Y. F. Li, S. Y. Dai and M. D. Wei, Nano Energy, 2014, 5, 82-90. 

J. Tian, Y. H. Sang, Z. H. Zhao, W. J. Zhou, D. Z. Wang, X. L. Kang, H. Liu, J. Y. Wang, S. W. Chen, H. Q. Cai and H. Huang, Small, 2013, 9, 3864-3872.

Acknowledgement

This work was financially supported by the National Natural Science Foundation of China (Grant 21273195).
Dental Amalgam As an Electrode Material for the Electrochemical Conversion of Carbon Dioxide
Authors: Park Mijung , Yoon Sumi , Kim Jina , Shin Woonsup
Published: February 2020

Currently many researchers are interested in electrochemical conversion of carbon dioxide (CO2) to formate and various materials including tin, tin oxide nanoparticle, copper oxide nanoparticle, etc. have been used. However, long-term stability in CO2 conversion has not been reported yet. We applied dental amalgam as a new electrode material and it could effectively produce formate with a current efficiency of 80~90% at 5~100 mA∙cm-2 for more than 200 hours.
''one-Pot'' Graphene Sheets Functionalization during the Electrochemical Exfoliation of Graphite
Authors: Ossonon Diby Benjamin , Bélanger Daniel
Published: February 2020

Graphene is undoubtedly one of the most attractive material for researchers, consequently the most intensively studied material due to its potential applications in several different areas. Various approaches are being developed for its large-scale preparation by green and cost-effective method. One of the best methods is the electrochemical exfoliation of graphite in an aqueous solution. However, for several applications graphene must be functionalized either non-covalently or covalently. In this work, graphene sheets produced electrochemically were functionalized during the exfoliation process. The resulting materials were characterized by several techniques such as Raman spectroscopy, thermogravimetric analysis, TEM, SEM, electronic conductivity measurements and electrochemical techniques.
Degradation Phenomenon of Ni-YSZ Anode Support Cells Under Various Operating Conditions
Authors: Park Jun-Young , Kim Youdong , Saqib Muhammad
Published: February 2020

Solid oxide fuel cells (SOFCs) is an electrochemical device which can directly convert chemical energy to electrical energy. They have many advantages including the high efficiency and multi-fuel flexibility. [1,2] Although high temperature-SOFCs have advantages in terms of performances high production cost and the limited durability are one of issues for making commercialization of SOFCs. Generally, SOFCs are required over 40,000 h life-time to enter into the real markets. [3,4] Furthermore, SOFCs should produce electrical power stably under a variety of severe operating conditions, such as thermal cycle, sudden electrical load change, and frequent electrical load cycle.

In this study, various accelerating degradation testing are performed to find the degradation patterns and disclose the main degradation mechanism of SOFCs. The durability of SOFCs are tested on a variety conditions of load trip and load cycle. The load trip is cycled at the current density of between 0 and 200 mA cm-2 at 700oC. Each step is held at 12 h and repeated 30 times. The load cycle is cycled under the current density of between 120 and 200 mA cm-2 at 700oC. Each step is held at 12 h and repeated 12 times. The thermal cycle is tested at 700oC and ramped down at 1℃ min-1 to 400oC. This step is repeated 30 times.

As a periodic diagnostic tool of I-V (current-voltage) characterization and electrochemical impedance analysis are performed cells, using an electrochemical impedance spectroscopy (EIS) with a Potentiostat/Galvanostant device using a frequency range from 1 MHz to 1Hz. The physicochemical analysis of tested cell are carried out using field emission-scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD).

1. Steele, Brian CH, and Angelika Heinzel. "Materials for fuel-cell technologies."Nature 414.6861 (2001): 345-352.

2. Yamamoto, Osamu. "Solid oxide fuel cells: fundamental aspects and prospects." Electrochimica Acta 45.15 (2000): 2423-2435.

3. Khan, Muhammad Shirjeel, et al. "Fundamental mechanisms involved in the degradation of nickel–yttria stabilized zirconia (Ni–YSZ) anode during solid oxide fuel cells operation: A review." Ceramics International 42.1 (2016): 35-48.

4. Hagen, Anke, et al. "Durability study of SOFCs under cycling current load conditions." Fuel Cells 9.6 (2009): 814-822.

* Corresponding author: jyoung@sejong.ac.kr (J.-Y. Park).
Electrodeposition of Cumn from a Deep Eutectic Electrolyte
Authors: Wu Pu-Wei , Chiang Wei-Shen , Hsu Chia-Yun , Chung Tsai-Wei , Chen Po-Chun , Dordi Yezdi , Joi Aniruddha
Published: February 2020

We demonstrate our recent progress in conducting electrodeposition of CuMn thin film using a deep eutectic solvent, which consists of CHCl and ethyl glycol. The sources for Cu ions and Mn ions are C10H14CuO4 and MnCl2, respectively. Plating methods such as potentiostatic, galvanostatic, and current pulsing have been explored with relevant electrochemical parameters optimized and discussed. We determine that the current pulsing route enables the formation of CuMn thin film with desirable Mn amount. Material characterizations including Scanning Electron Microscopy, X-ray diffraction, X-ray Photoelectron Spectroscopy, and X-ray Absorption Microscopy have been carried out. Our results indicate that Mn exists in both metallic form and oxide, and after heat treatment, precipitates with excess Mn are found on the surface. In addition, the conductivity of deep eutectic electrolyte is greatly affected by the ambient moisture and consequently, the plating process is kept in a glovebox to minimize unnecessary interference.
Quasi-Solid-State Dye-Sensitized Solar Cell with Ionic Gel Electrolytes By Semifluorinated Alkoxy Benzene Derivative
Authors: Cao Banpeng , Kaneshige Yuta , Morita Yuki , Okamoto Hiroaki
Published: February 2020

Quasi-solid-state dye-sensitized solar cells (QS-DSSCs) have rapidly become an important research orientation in electronic vehicles. Especially, ionic liquid gel electrolytes (ILGEs) solidified by low molecular mass organogelators (LMOGs) can effectively possess higher ionic conductivity and good pore filling.1 Based on the advantage of ILGEs, we present here a kind of LMOGs (compounds 1(n)) by semifluorinated benzene derivatives.

ILGEs formed by compounds 1(n) with different ionic liquids can divide two parts. One is with the representative [BMIM] posion-based ionic liquids (ILs), such as [BMIM] [I], [BMIM] [BF4], [BMIM] [FSA] and [BMIM] [TFSA]. Another one is with the representative [TFSA] anion-based ILs, such as [DEME] [TFSA], [EMIM] [TFSA], [TMPA] [TFSA], [AAIM] [TFSA] and [P13] [TFSA]. The minimum gelation concentrations in weight percent were determined at concentrations ranging from 5% to 1% in a heating-cooling cycle by the “stable to inversion in a test tube” method. The thermal properties of ILGEs which exactly is the effect of the concentration on the gel-sol phase transition temperatures (T gel) upon heating were examined. The ionic conductivity (σ) of ILGEs which is an important property for ILGEs was also examined. Compared with the data of ionic conductivities which has been reported in literature, it was found that the ionic conductivities in gel state were similar with ionic conductivities in liquid state. The conductivities of ILGEs with different concentrations of LMOGs were also analyzed.

The diffusion of redox couple (I3
- and I-) ions in the ILGEs is an important factor for DSSCs property.2 In order to analyze the behavior of in I3
- and I- the ILGEs, linear sweep voltammetry studies were performed at a scan rate of 1.0 mVs-1 at room temperature. The performance of [BMIM] [I] was different with others. It maybe that ionic liquid of [BMIM] [I] contains anion of I- by itself.

Reference

1. (a) Wang, P.; Zakeeruddin, S. M.; Comte, P.; Exnar, I.; Grätzel, M. Gelation of ionic liquid-based electrolytes with silica nanoparticles for quasi-solid-state dye-sensitized solar cells. Journal of the American Chemical Society
2003,
125 (5), 1166-1167; (b) Tao, L.; Huo, Z.; Ding, Y.; Li, Y.; Dai, S.; Wang, L.; Zhu, J.; Pan, X.; Zhang, B.; Yao, J. High-efficiency and stable quasi-solid-state dye-sensitized solar cell based on low molecular mass organogelator electrolyte. Journal of Materials Chemistry A
2015,
3 (5), 2344-2352.

2. Yoon, J.; ki Kang, D.; Won, J.; Park, J.-Y.; Kang, Y. S. Dye-sensitized solar cells using ion-gel electrolytes for long-term stability. Journal of Power Sources
2012,
201, 395-401.
Morphology in Porous Silicon Prepared from Si-Nanowires Grown By Electroless Etching
Authors: Velez Victor H. , Sundaram Kalpathy B
Published: February 2020

Porous silicon nanowires (SiNWs) shown remarkable advantages due to the chemical and physical properties [1]. These properties cause special interest in optoelectronics and sensing applications [2]. Porous silicon nanowires were prepared in an electrolytic solution concentration after grown these nanostructures in an electroless etching solution [3]. Changes in the morphology of porous SiNWs may be the result of increasing the concentration of the oxidizer (C2H6O) and etching time when these nanoparticles are etched in an electrolytic solution. SiNW arrays grown by electroless etching is shown in Figure 1a. Further changes are achieved in the diameter and length when the prepared electroless SiNW arrays are etched in an anodic solution to reduce its quantum confinement to obtain porous silicon nanowires, as shown in Figure 1b. Silicon nanowires were grown by electroless etching in an etching solution concentrations of hydrofluoric Acid (HF) and silver nitrate (AgNO3) at room temperature [4]. The prepared nanowires were then etched in an electrolytic solution containing HF and ethanol to make porous Si quantum confinement structures. SEM images were obtained for morphology analysis.

 

Figure 1
(Invited) Study of Lithium-Ion Cell Degradation Behavior Under Multiple Stresses
Authors: Zhang Jianbo , Su Laisuo , Zhang Yakun , Zhang Jianyu , Li Xinyu , Li Zhe , Liaw Bor Yann
Published: February 2020

Cycling and storage are two typical tests in laboratory to evaluate the degradation behavior of lithium-ion cells (LIC). In real world application, however, LIC is always under the stress of multi-factors with no predefined sequence. This work addresses some of the intriguing issues in the study of the degradation behavior of LIC under multiple-stressors: the effect of different stresses on degradation rate, boundary demarcation between accelerated stress test and abuse, life prediction, path dependence, and lithium plating detection techniques, etc. The techniques developed and the insight gained are crucial to the degradation mechanism identification, charging protocol optimization, and life prediction. (1) A generic cycling profile, for which the storage is just a special case, was devised to study the main effects of the seven key stress factors, using L18(2×37) orthogonal matrix in design of experiment (DOE). Orders of the key stress factor’ impacts on capacity degradation were obtained. (2) L27(313) was employed to study the effects of the levels of three key stress factors. Close examination of the test results led to a method demarking the boundary between accelerated stress test and abuse that may lead to lithium plating. (3) Within the obtained non-abuse boundary, orthogonal regression design method with 28 tests was used to build an empirical aging model, which was validated with four independent cycling conditions. (4) Storage tests using different thermal excursion profiles were devised to evaluate path dependence characteristics of the cell capacity degradation and resistance variations. (5) Based on the degradation behaviors, three techniques were explored to evaluate whether there has been lithium plating during the cycling. The prediction was validated with the post-mortem analysis.
(Invited) Lithium Rich Layered Materials − Electrochemical Properties of Epitaxial Film Electrodes
Authors: Kanno Ryoji , Taminato Sou , Hikima Kazuhiro , Mizuno Yoshifumi , Suzuki Kota , Hirayama Masaaki
Published: February 2020

Structures, electrochemical properties and reaction mechanism of lithium rich layered cathode materials, Li2
MO3 (M = transition metals), were studied for the epitaxial-films fabricated by pulsed laser deposition methods. Their charge-discharge characteristics were investigated both for the liquid and solid electrolyte systems and the lithium intercalation-deintercalation reactions were studied using surface X-ray diffraction and hard X-ray photoelectron spectroscopy. The charge-discharge capacities drastically increased with decreasing film thickness for the Li2MnO3 using liquid electrolyte. The 12.6 nm thick film showed higher capacity over 300 mA h g-1 and better stability compared to the 29.8 and 47.8 nm thick films. The dependence of the electrochemical properties on the film thickness demonstrates that the surface region is actively reconstructed to generate a high capacity phase with high electrochemical stability. The structure analysis also indicated that the surface structural changes at the initial cycling have a pronounced effect on the power characteristics and the capacity of lithium-rich layered rocksalt type cathodes. On the other hand, the Li2MnO3 using solid electrolytes showed higher charge-discharge capacity and better stability after 100 cycles than the liquid system. Surface structure analysis indicates a different phase change during the cycling from the liquid system. The reactions at the solid/solid interface could contribute to the phase changes at the surface region and also to the cycling degradation of these lithium rich phases.
Optoelectronics and Electrochemical Properties of RuO2/PEDOT:PSS Transparent, Conductive Ultrathin Films
Authors: Zhang Chuanfang , Higgins Thomas , Park Sang Hoon , Coleman Jonathan N , Nicolosi Valeria
Published: February 2020

Transparent, conductive electrodes are important in many applications such as touch screens, displays and solar cells. Transparent energy storage systems will require materials that can simultaneously act as current collectors and active storage media. This is challenging as it means improving the energy storage capability of conducting materials while retaining transparency. Here, we have used aerosol-jet spraying strategy to prepare transparent supercapacitor electrodes from ruthenium oxide/poly(3,4-ethylenedioxythiophene): poly(styrene-4-sulfonate), (RuO2/PEDOT:PSS) hybrid thin films. These films combine excellent transparency with reasonably high conductivity (DC conductivity =279 S/cm) and excellent volumetric capacitance (CV
=190 F/cm3). We demonstrate electrodes with transparency of 93% which display an areal capacitance of C/A=1.2 mF/cm2, significantly higher than the rest reported electrodes with comparable transparency. We have assembled flexible, transparent, solid-state symmetric devices which exhibit T=80% and C/A=0.84 mF/cm2 and are stable over 10,000 charge/discharge cycles. Asymmetric solid-state device with RuO2/PEDOT:PSS and PEDOT:PSS thin films as positive and negative electrodes, respectively, display an areal capacitances of 1.06 mF/cm2, a maximum power density (P/A) of 147 μW/cm2 and an energy density (E/A) of 0.053 μWh/cm2. Furthermore, large area transparent solid-state supercapacitor device has been built. We believe the solution-processed transparent films could be easily scaled-up to meet the industrial demands.
Directly-Grown Hierarchical Carbon Nanotube@Polypyrrole Core-Shell Hybrid on Carbon Cloth As a High-Performance Flexible Supercapacitor with High Cycle Stability
Authors: Shown Indrajit , Yesi Yesi , Chen Li-Chyong , Chen Kuei-Hsien
Published: February 2020

Supercapacitors are attractive energy storage devices in the modern flexible and wearable electronics, owing to their high-energy density and high-power density in comparison with conventional capacitors and batteries, respectively. Among various pseudocapacitor materials, polypyrrole (PPy) is one of the most promising pseudocapacitor materials due to its easy polymerization, high conductivity, nontoxicity, and unique doping process with a wide range of dopant, a greater degree of flexibility than other conducting polymers, moderately high theoretical specific capacitance with potential operating potential window around 0.8 V and its good stability in ambient atmosphere. However, the PPy-based pseudocapacitor is still suffering from its limited cycling stability and high interfacial resistance.[1] In this study, we have fabricated hierarchical CNTs-PPy core-shell hybrid on flexible carbon cloth by binder free direct growth method for flexible supercapacitor application. In particular, deposition of in-situ doped PPy-shell on the CNT-core is done by simple electropolymerization with controlled shell thickness. Direct fabrication of electroactive (CNTs-PPy) materials on the flexible CC electrode could reduce the interfacial resistance between the electrode and electrolyte and improve the ion diffusion process. The supercapacitor electrode based on optimized PPy/CNTs-CC exhibits excellent electrochemical performance, indicating highest gravimetric capacitance around 486.1 F g-1 per active mass of the PPy/CNTs composite with excellent flexibility and cycle stability up to 10,000 cycles with only 18% capacitance loss.[2] At the same time, the fabricated asymmetric supercapacitor (PPy/CNTs-CC║CNTs-CC) shows the maximum power density of 10,962 W kg-1 at an energy density of 3.9 Wh kg-1 under the operating potential of 1.4 V. The detail pouch type symmetric and asymmetric supercapacitor performance together with electrochemical test will be discussed on the presentation.

 

References

[1] I. Shown, A. Ganguly, L.-C. Chen and K.-H. Chen, Energy Science & Engineering, 2015, 3, 2-26.

[2] Y. Yesi, I. Shown, A. Ganguly, T.-T. Ngo, L.-C. Chen, K.-H. Chen, ChemSusChem,
2016, 9,370-378.
High Performance Pseudocapacitors Based on Multicomponent Transition Metal Oxides By Local Distortion of Oxygen Octahedra
Authors: Lee Hyeon Jeong , Lee Ji Hoon , Choi Jang Wook
Published: February 2020

As pseudo-capacitors store the charge based on the dual (‘faradaic’ and ‘capacitive’) modes, they have the advantages of both ultracapacitors and rechargeable batteries.[1] One of the main directions in pseudo-capacitor research in the past decade has been the integration of nanostructured metal oxides, hydroxides, and chalcogenides with conductive carbon nanomaterials,[2] such as graphene and carbon nanotubes. Nanostructures bring the benefits of high rate capability as well as long cycle life related to the improved mechanical stability of active phases, as nanomaterials are better at releasing the strains. The nanostructure effect of metal oxides was verified for a variety of morphologies with diverse transition metals.[3]Nonetheless, a majority of studies have focused solely on the nanostructure effects, and the impact of the TM choice or mixing of multiple TMs on the electrochemical performance has not been examined in depth.

Here, we have systematically investigated the impact of multiple TMs, particularly those commonly adopted as pseudo-capacitor active materials: Ni, Co, and Mn. Interestingly, when the three TMs are mixed in equal amounts, the specific capacitance rises far beyond those of their individual cases, indicating a synergistic effect from the TM mixing. A combined experimental and theoretical analysis reveals that the enhanced performance originates from permanent local distortions of [NiO6] octahedra in the presence of aliovalent cations (Co3+ and Mn4+) and transition metal vacancies (V
M), among which V
M has the largest effect on distorting the nearest neighboring [NiO6] octahedra. The degenerate eg
level in Ni2+, the primary redox center for capacitance acquisition, is split via this permanent distortion, thus enabling the energetically more facile redox swing of Ni2+/3+by alleviating the structural variation from a Jahn-Teller effect.

This study introduces a new opportunity to improve the electrochemical performance of pseudo-capacitors through the mixing of multiple TM cations. The solid solution mixing of multiple TMs pre-distorts the framework and consequently mitigates Jahn–Teller-type structural variation during the redox reaction, resulting in the significantly wider redox swing of Ni and the larger pseudo-capacitance of the solid solutions. The findings of this study demonstrate the importance of structure-property relation in designing and improving key active materials in emerging energy storage systems.

References

[1] Simon, P., Gogotsi, Y., Nat. Mater.
2008,
7, 845-854.

[2] Yu, G., Hu, L., Liu, N., Wang, H., Vosgueritchian, M., Yang, Y., Cui, Y., Bao, Z., Nano Lett.
2011,
11, 4438-4442

[3] Lu, Q., Chen, J. G. G., Xiao, J. Q., Angew. Chem. Int. Ed.
2013,
52, 1882-1889
Flexible and Weaveable Wire-Shaped Capacitor with Ultra-High Energy Density
Authors: Cheng Jianli , Wang Bin
Published: February 2020

Wearable electronics and microelectronics have been shown to be highly desired in the current and further life. To power these wearable electronic systems, flexible energy storage devices are needed. Comparing with the conventional planar device architectures, one-dimensional fiber micro-supercapacitors (FSCs) with the merits of lightweight, tiny volume, high flexibility and weavability which can be directly used as wearable components are more attractive. However, compared with batteries or traditional capacitors, FSCs show much lower-energy density and suffer from extra challenges in mechanical performance. According to the equation (E = 0.5CU2), energy is proportional to capacitance. So it is crucial to explore high capacitance fibers with good mechanical properties for FSCs.

  Electric-double layer capacitors (EDLCs) store energy through the charge separation at the electrode/electrolyte interface. In our study, we try to increase the capacitance and energy density of EDLCs by increasing the fiber interfacial area. We adopt a simple pipe mold method to fabricate hollow RGO/PEDOT composite fibers and hollow pure RGO fibers (labeled as HCFs and HPFs) with excellent flexibility and conductivity. Furthermore, the hollow fibers show a dramatic charge-storage ability. The symmetric solid-state FSCs composed of two HCFs reveal a high specific areal capacitance of 304.5 mF cm-2 at 0.08 mA cm-2, corresponding to an ultra-high energy density of 6.8 µWh cm-2 at a power density of 16.6 µW cm-2. To the best of our knowledge, it is the highest record for FSCs to date.

 In this presentation, we will discuss the fiber formation mechanism, charge storage mechanism and we will display the flexible wire-shaped energy device constructed by the one-dimensional fiber micro-supercapacitors.
(Invited) The Development of Pseudocapacitance in Oxide Materials
Authors: Dunn Bruce
Published: February 2020

Battery materials exhibit high energy density by utilizing reversible redox reactions, but their slow ionic diffusion leads to long charging times. Electrochemical double layer capacitors (ELDCs) offer some advantages over batteries, including fast charging times (<1 minute) and long lifetimes (<500,000 cycles). However, ELDCs do not involve redox reactions and as a result they have lower energy densities compared to batteries. For this reason, there is widespread interest in pseudocapacitance, a faradaic process involving surface or near-surface redox reactions, that can lead to high energy density at high charge-discharge rates. In recent work, we have suggested that pseudocapacitive materials can be classified as extrinsic or intrinsic; in the latter case, pseudocapacitive behavior is dependent on particle size, as fundamental changes in redox reactions may occur in finite sized systems. This paper will review our work on identifying Li+ conducting materials which exhibit pseudocapacitive behavior. Our research on Li+ insertion in Nb2O5 has established a basis for intercalation pseudocapacitance in which the rate of charge storage is determined by surface-like kinetics rather than semi-infinite diffusion as occurs with battery materials. Another key feature with this mechanism is that the structure does not undergo a phase transformation upon Li+ insertion. However, even with materials that exhibit phase transitions, such as MoO2, pseudocapacitive properties may be observed provided that the materials are reduced to nanoscale dimensions. In this case pseudocapacitive characteristics arise because phase transitions which occur in the corresponding bulk material are effectively suppressed. Our research with nanoscale MoO2 shows that pseudocapacitive properties are developed and that the material operates at high charge-discharge rates with only a small decrease in the level of charge storage. In contrast, micron-sized particles exhibit a significant decrease in charge storage at high charge-discharge rates. These results underscore our improved understanding of the electrochemical and structural characteristics that lead to materials that exhibit both high energy density and high power density.
Ba0.5Sr0.5CoxFe1-XO3-d As High Volumetric Capacitance Pseudocapacitive Electrode Materials
Authors: Lannelongue Pierre , Brousse Thierry , Crosnier Olivier , Favier Frederic
Published: February 2020

The design and fabrication of high volumetric energy density supercapacitors lead to high density pseudocapacitive materials to be considered as electrode material. After our previous, and still on-going, work on FeWO4 [1], Ba0.5Sr0.5CoxFe1-xO3-
δ phases, with 0.75<x<0.85, so-called BSCF, are currently under investigation. Our motivation towards these materials are (i) on the sub-stoechiometry in oxygen suggesting a flexible balance of either Fe and Co redox centers as well as (ii) on their attractive intrinsic electronic conductivity. These phases have been prepared by various synthetic methods, including Pechini and flash combustion syntheses, at various temperatures ranging from 850 to 950 °C. Despite the eventual presence of small amount of CoO and BaO impurities (depending on the synthesis type and temperature), resulting materials show the same perovskite structural arrangement and similar morphological characteristics.

The electrochemical performances have been evaluated by cyclic voltamperometry at room temperature, at various scan rates from 5 to 200 mV.s-1 and in various aqueous electrolytes: KOH 0.5 M, H2SO4 0.5 M, K2SO4 0.5 M, Na2SO4 0.5 M, Li2SO4 0.5 M, and LiNO3 0.5, 1.0 and 5 M. The potential window was shown to vary depending on the electrolyte nature but, most of the time, prepared BSCFs showed promising pseudocapacitive behaviors as electrode material. A specific capacitance of 64 F.g-1 was measured at 5 mV.s-1 in LiNO3 5M for the electrode based on the material prepared by flash combustion at 850°C. This value corresponds to a volumetric capacitance of 377 F.cm-3. The electrode also exhibited fair capacitance retention over 2000 cycles.

The electrochemical performances were shown to vary depending on the Co/Fe ratio and are discussed toward the involved charge storage mechanism.

Reference

[1] N. Goubard-Bretesché, O. Crosnier, C. Payen, F. Favier, T. Brousse, Electrochem. Com. 57, 61–64, 2015
Understanding Pseudocapacitive Charge Storage in Transition Metal Oxides from Fundamental Interfacial Processes to 3D Electrode Design
Authors: Long Jeffrey W. , Sassin Megan B. , Chervin Christopher N. , Parker Joseph F. , Wallace Jean Marie , Rolison Debra R.
Published: February 2020

Transition-metal oxides that exhibit “pseudocapacitance” are promising alternatives to high-surface-area carbons as charge-storing materials in next-generation electrochemical capacitors (ECs). Hydrous ruthenium oxides remain the state-of-the-art for pseudocapacitive materials due to their fortuitous combination of high electronic and ionic conductivity. Lower-cost alternatives are being vigorously pursued, yet the low electronic conductivity of most other metal oxides of interest (e.g., MnOx) necessitates that they be thoughtfully incorporated with a conductive carbon support. We have developed an electrode design in which pseudocapacitive oxides, such as MnOx and FeOx, are applied as nanoscale coatings onto ultraporous carbon nanofoam substrates that define the macroscale-to-nanoscale structure of the resulting electrode architecture [1,2]. In addition to their practical advantages for device fabrication, these nanofoam paper-based materials have also provided a designer platform with which to investigate the interplay of pore structure and electrochemical performance [3] and for in situ analysis of the mechanisms responsible for pseudocapacitance [4].

In the background of these studies, we have accumulated evidence that the physicochemical nature of the carbon–metal oxide interface can have a significant impact on electrochemical performance. While continuing to develop and transition our 3D electrode architectures, we are refocusing our research efforts on investigating fundamental charge-transfer properties at nanoscale carbon–metal oxide interfaces. Shifting from the characterization complexities of the nanofoam-based architectures, we use planar pyrolytic-carbon substrates to mimic the surface properties of 3D carbon, but in forms that are more readily characterized by conventional surface spectroscopy and scanning-probe microcopy techniques. We apply nanoscale pseuodocapacitive oxides to these planar carbon films using redox-deposition protocols previously demonstrated at 3D carbons [5], and explore how the physical, chemical, and electronic structure of the resulting carbon–metal oxide interface impacts electrochemical properties. Lessons learned from these model interfaces are readily translated to improved performance in practical 3D electrode architectures.

1. Fischer, A.E.; Saunders, M.P.; Pettigrew, K.A.; Rolison, D.R.; Long, J.W. J. Electrochem. Soc. 2008, 155, A246.

2. Sassin, M.B.; Mansour, A.N.; Pettigrew, K.A.; Rolison, D.R.; Long, J.W. ACS Nano
2009, 4, 4505.

3. Sassin, M.B.; Hoag, C.P.; Willis, B.T.; Kucko, N.W.; Rolison, D.R.; Long, J.W. Nanoscale, 2013, 5, 1649.

4. Beasley, C.A.; Sassin, M.B.; Long, J.W. J. Electrochem. Soc.
2015, 162, A5060.

5. Sassin, M.B. Chervin, C.N.; Rolison, D.R.; Long, J.W. Acc. Chem. Res.
2013, 46, 1062.
Ionic Liquid Mxene-Based Pseudocapacitors
Authors: Alhabeb Mohamed , Van Aken Katherine L , Anasori Babak , Gogotsi Yury
Published: February 2020

Pseudocapacitors are types of electrochemical capacitors in which energy is stored via surface redox reactions rather than ion adsorption mechanisms as in electric double layer capacitors. Among two dimensional (2D) materials, MXenes are a newly discovered family of transitional metal carbides and/or carbonitrides with ≈ 20 synthesized members and over 30 members predicted to exist, making it not only the fastest growing but potentially the largest family ever known 2D materials[1-3]. In contrast to other well known 2D materials, the unique combination of a metal carbide and surface termination groups of MXenes make them exceptionally hydrophilic and highly conductive. Titanium carbide MXene (Ti3C2), in particular, has shown outstanding capacitive performance in aqueous electrolytes due to its superior metallic conductivity[4, 5].

Here, we pre-intercalated Ti3C2 binder free electrodes with ionic liquids (ILs) to enhance the interlayer spacing of the electrode material, which shows excellent capacitive performance up to 200 F/g and energy density of 100 W.h/kg. We also report on using two of the newly discovered molybdenum and chromium containing MXenes, Mo2TiC2, and Cr2TiC2 free-standing films as pseudocapacitor electrodes in ILs electrolytes. The use of ILs enables us to increase the operating voltage window of MXene based electrodes and results in high energy density in comparison to aqueous electrolytes. This study opens new window for MXene based electrodes in applications that requires high energy density.

References:

1. Naguib, M., et al., Two
‐
Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Advanced Materials, 2011. 23(37): p. 4248-4253.

2. Anasori, B., et al., Two-Dimensional, Ordered, Double Transition Metals Carbides (MXenes). ACS Nano, 2015.

3. Naguib, M. and Y. Gogotsi, Synthesis of two-dimensional materials by selective extraction. Acc Chem Res, 2015. 48(1): p. 128-35.

4. Lukatskaya, M.R., et al., Cation intercalation and high volumetric capacitance of two-dimensional titanium carbide. Science, 2013. 341(6153): p. 1502-5.

5. Ghidiu, M., et al., Conductive two-dimensional titanium carbide/clay/'with high volumetric capacitance. Nature, 2014. 516(7529): p. 78-81.
Activation of Petroleum Pitch for Production of Porous Carbons with High Electric Double Layer Capacitance
Authors: Wu Pin-i , Teng Hsisheng
Published: February 2020

Petroleum pitch can be an alternative of coal tar pitch as the precursor of activated carbon because of their lower contents of detrimental impurities and less pollution to the environment when compared with coal tar pitch. High-porosity carbon derived from activation of mesophase pitch with KOH has been successfully used as the electrode materials for electric double layer capacitors (EDLCs).1 Formation of mesophase structure through thermal treatment coordinates the pitch molecules and eventually reinforces the structure of porous carbons obtained from activation. The present study devises a temperature-programmed heating strategy to convert petroleum pitch to mesophase that has a framework advantageous for producing porous carbons suitable for EDLCs. The porous carbon is synthesized by KOH activation and has a Brunauer-Emmett-Teller surface area exceeding 3000 m2/g, When assembled in a symmetric two-electrode cell, the carbon delivers capacitance values of 170 and 102 F g-1 at current densities of 0.5 and 100 A g-1, respectively, in 1 M tetraethylammonium tetrafluoroborate/acetonitrile electrolyte. The energy density of the cell based on the total carbon mass reaches 23 Wh kg-
1 at a power density of 40 kW kg-
1. The results of the present study demonstrate the feasibility of using petroleum pitch as the precursor for porous carbon production and the significance of mesophase pitch structure for regulating the structure of pores suitable for charge storage.

 

References

1. H.C. Huang, C.J. Chung, C.T. Hsieh, P.L. Kuo, H. Teng, Nano Energy 21 (2016), 90

Acknowledgments: This research was supported by the Ministry of Science and Technology, Taiwan (104-2221-E-006-231-MY3, 104-2221-E-006-234-MY3, 105-3113-E-006-005, and 104-3113-E-006-011-CC2), and by the Ministry of Education, Taiwan, The Aim for the Top University Project to the National Cheng Kung University.
Fabrication and Enhanced Electrochemical Properties of Bi3.64Mo0.36O6.55 Nanoparticles with a High Bi Content for Pseudocapacitor Electrodes
Authors: Liu Xiaoheng , Zhu Dan , Wang Weiwei
Published: February 2020

The faradaic pseudocapacitors are emerging as an attractive energy-storage solution with much higher specific capacitance and energy density due to their reversible multielectron redox faradaic reactions.Herein, we reported that the monodisperse Bi3.64Mo0.36O6.55 nanoparticles could be used as a novel pseudocapacitor electrodes material. This nanoparticles could be successfully prepared by a facile hydrothermal method using sodium molybdate (Na2MoO4·2H2O) and bismuth nitrate (Bi(NO3)3·5H2O) as the Mo and Bi sources, respectively. The technologies of X-ray powder diﬀraction (XRD), X-ray photoelectron spectroscopy (XPS), ﬁeld emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and selected area electronic diﬀraction (SAED) were used to characterize the structure and morphology of Bi3.64Mo0.36O6.55 nanoparticles. The results show that the dimensions of the as-prepared Bi3.64Mo0.36O6.55 nanoparticles are 100-150 nm. The pseudocapacitive properties of products were investigated at the redox potential of -1.0-0 V vs. Hg/HgO in a 1 M aqueous KOH solution by cyclic voltammetry (CV), chronopotentiometry (CP) and AC impendence. The higher specific capacitance could be obtained as about 998 F/g compared with that of Bi2MoO6 (350 F/g) at 1 A/g, which is possibly ascribed to the nanoparticle structure and the exceeded Bi content of Bi3.64Mo0.36O6.55 nanoparticles. Furthermore, the Bi3.64Mo0.36O6.55 nanoparticles electrode exhibits a good cycle stability with more than 95% after 1000 cycles. These results demonstrated that the obtained high performance Bi3.64Mo0.36O6.55 nanoparticles could be a promising electrode material for pseudocapacitor.
A Combined Theoretical-Experimental Study of Energy Storage Behavior of Reduced Graphene Oxide/Manganese Oxide Supercapacitor
Authors: Lee Chan-Woo , Byun Segi , Yoo Jung-Joon
Published: February 2020

Miniaturized electrochemical capacitors, such as micro-supercapacitors, have emerged as a new class of micro-power sources. However, they have limited uses in micro-energy storage because of their low volumetric energy densities. Here, compact structured Birnessite (MnO2)/reduced graphene oxide (RGO) hybrid films (Fig.1) consisting of multi-valent Mn ions were prepared via a two-step fabrication process involving a simple chemical redox reaction and post-thermal annealing to form a multi-layer structured film. With this versatile method, GO sheets can act as either a growth template for the highly capacitive MnO2 nanosheets or as a mechanical support for the production of compact hybrid films. Enhanced electrochemical characterization of the MnO2/RGO hybrid film revealed a remarkable ultrahigh volumetric capacitance (493 F/cm3 at 10 mV/s), ultrahigh energy and power density (13.3 mWh/cm3 at 2.5 A/cm3 and 22.6 W/cm3 at 58 A/cm3, respectively) and a semi-permanent cycle life (97% capacitance retention) in an aqueous electrolyte system.

We also elucidated operating mechanisms of MnO2/RGO capacitor using state-of-the-art density-functional theory calculations with MnO2 nanoparticle/RGO sheet models. Various materials properties of MnO2/RGO systems including stoichiometric deviation, defect energetics, electron transfer, and kinetic behavior of cations and their contributions to their capacitance have been explored in atomic level.

Figure 1