bluuebunny/crossref_metadata_2025 huggingface dataset:
Organic Photovoltaic Switches Using DBP/C60 Cells and Blue Light to Trigger Logic and Amplifier Electronics
Authors: Ahn Jongtae , Lim June Yeong , Park Sam , Im Seongil
Published: February 2020

Apart from ordinary solar cell applications, we have attempted different approaches of device applications. We have fabricated two types of organic photovoltaic (OPV) cells with DBP/C60 heterojunction and measured their spectral photo responses when they are in planar heterojunction (PHJ) and bulk heterojunction (BHJ) type. According to our results, blue light exhibits spectrally outstanding PV effects and the PHJ device showed higher open circuit voltage (VOC) along with ten times faster switching photo-dynamics than those performances of BHJ device, although the mixture type BHJ diode appears much superior to PHJ diode in all spectral ranges of quantum efficiency. Large junction area of mixture type OPV diode is certainly an advantage in photocurrent generation and quantum efficiency, but is regarded as a disadvantage for dynamic PV switching and VOC value because complex route and high density interface traps are unavoidable in BHJ structure. Selecting the blue light illumination on DBP/C60 PHJ diode, we achieve most efficient PV switching and PV gating in logic and amplifier circuits, respectively. Conclusively, bilayer OPV device has its own advantage over mixture type device in dynamic PV switching, and it promises future electronics by exploiting the dynamic harvest of light energy.

Figure 1
(Invited) Nanoscale Electrocrystallization: A Site-Selective Electrochemical π-Figuration of Nanocrystals for Electronic Devices
Authors: Hasegawa Hiroyuki
Published: February 2020

Efficient nanofabrication is still the problem awaiting solution in the nanotechnology field. Such nanofabrication should involve both economy and ecology-friendly process which produces high performance materials or devices. As seen in semiconductor industry, these fabrication technologies generally consume a large amount of energy under high-vacuum and/or high-temperature conditions. There is a strong need to switch to processes which are both eco-friendly and low-cost. Therefore pinpoint nanofabrication via eco-friendly process seems to be most promising.

From the viewpoint, we have developed nanoscale electrocrystallization for nanodevice fabrication.1 This method allows everyone to grow nanocrystals, which consist of π-conjugated molecules, site-selectively within a gap between two electrodes fabricated on a substrate. In addition, this method also allows for the gap between the two electrodes to be bridged by the formed nanocrystals.

· Magnetic field effect devices

Magnetic field effect devices were designed by using dicyanoiron(III)phthalocyanine ([Fe(Pc)(CN)2]-) tetraphenylphosphonium (TPP+) salt as a starting material of nanoscale electrocrystallization. The electrolysis gave nanocrystals that exhibited a strong correlation between the localized spin and conduction electrons, TPP·[Fe(Pc)(CN)2]2 was obtained. A negative giant magnetoresistance was first observed as an organic nanocrystal.2 Moreover, an angular dependence of the negative giant magnetoresistance that originates from the highly oriented growth of the nanocrystals was also observed.

· Electronic field effect devices

Electronic field effect devices such as field-effect transistors (FETs) were designed by using materials for organic conductors. A bottom-gate type FET structure was simply obtained when a silicon substrate with oxide layer was used for an electrode substrate. The two electrochemical electrodes were reused as source and drain electrodes. FET characteristics showed current enhancement in some kinds of samples.3 The device fabrication was also demonstrated via an eco-friendly and non-vacuum process using a material printer.4

Further details of fabrication, materials, and physical properties will be reported.

References

1. H. Hasegawa, T. Kubota, S. Mashiko, Thin Solid Films, 2003, 438–439, 352–355; H. Hasegawa, T. Kubota, S. Mashiko, Electrochim. Acta, 2005, 50, 3029–3032; H. Hasegawa, R. Ueda, T. Kubota, S. Mashiko, Thin Solid Films, 2006, 499, 289–292.

2. H. Hasegawa, M. Matsuda, H. Tajima, J. Mater. Chem. C, 2013, 1, 6416–6421.

3. H. Hasegawa, J. Mater. Chem. C, 2013, 1, 7890–7895; H. Hasegawa, New J. Chem., 2013, 37, 2271–2274; H. Hasegawa, Sci. Adv. Mater., 2014, 6, 1548-1552.

4. H. Hasegawa, Appl. Mater. Today, 2017, 9, 487–492.

Figure 1
Electrocatalytic Hydrogen Evolution Reaction Mediated By Co-Hangman-Xanthene-Chlorin Complexes
Authors: Liu Mengran , Dogutan Dilek , Costentin Cyrille , Nocera Daniel G
Published: February 2020

Chlorins have presented an interesting new class of catalysts for activation of small molecules of energy consequence, more specific, chlorins exhibited higher catalytic activity in hydrogen evolution at low overpotentials versus its porphyrin congeners. A hangman chlorin with a xanthene backbone and a carboxylic acid hanging group positioned above the redox-active macrocycle catalyzes the electrochemical production of hydrogen from trifluoroacetic acid (TFA) and benzoic acid in acetonitrile solutions. The hangman motif provides mechanistic insights into the role of pendant proton relays in governing proton-coupled electron transfer (PCET) involved in the HER. HER by Co chlorins in strong and weak acid reveals Co(II)H is exclusively involved in the generation of H2, but a hydrogen evolution mechanism proceeds by an ECEC mechanism in TFA solution or an EECC mechanism in benzoic acid solution, respectively. Overpotentials for H2 generation are lowered as a result of the hangman effect.
Anomalous Current/Voltage Behaviors of Polyoxometalate/Porphyrin Derivative Complexes
Authors: Ogawa Takuji , Nurhayati Nunik , Miyamoto Fumiya , Yamazaki Yoshito , Aoyama Tomoya , Yamashita Ken-ichi , Tani Yosuke
Published: February 2020

Polyoxometalate (POM) derivatives have been reported to show various specific electronic properties. For example, (NH4)6V10O28 and H7SiW9V3O40 show negative differential resistance (NDR) when measured by scanning tunneling spectroscopic (STS) technique in air.1,2 We have reported that a composite of H3PMo12O40 with single-walled carbon nanotubes (SWNT) showed complex phenomena depending on the size of the POM nanoparticles. When the size of the POM was smaller than ~6 nm with a semiconducting SWNT, the composite showed rectification with positive bias suppression. By contrast, if the size of the POM was larger, the suppression was observed at negative bias. However, when the SWNT is metallic, the suppression occurred at the opposite bias.3

There are several POM/porphyrin derivatives or analogues reported, saddle-distorted Mo(V)-dodecaphenylporphyrin with Keggin-type H2SiW12O40,4 cyclo[8]pyrrole with H4SiW12O40,5 tetraphenylporphyrin (TPP) with SW10V2O40.6 The electronic properties of these complexes are interesting to measure in macro-scale and in single molecule-scale, because of the versatile electronic behaviors are expected from multi redox characters of POM cores tuned by the surrounding porphyrin derivatives.

The single crystal structure of [H4TPP][SV2W10O40] was successfully determined, in which one POM anion is surrounded by four H4TPP cations. Although this complex is dissociated in solution, the casted sample retains crystalline structures partially as observed by the powder X-ray diffraction study. Devices were made by casting the solution of the complex on Au electrodes with 5 μm gap. The current-voltage curve at ambient conditions showed broad negative differential resistance (NDR) with large hysteresis. The impedance measurements between 10-1 to 106 Hz at 0.0 to 3.0 V DC bias indicated that in low frequency range (<10 Hz) the impedance is lower at high DC bias voltage. However, in high frequency range (> 10Hz) the impedance is almost independent on voltage. The impedance results indicate that non-linear NDR behavior observed in DC measurement is because of a slow process of the carrier movement, probably by ionic conductance.

References

(1) Ogawa, T.; Handayani, M. In Molecular Architectonics; Ogawa, T., Ed.; Springer Nature: Switzerland, 2017, p 419.

(2) Watson, B. A.; Barteau, M. A.; Haggerty, L.; Lenhoff, A. M.; Weber, R. S. Langmuir
1992, 8, 1145.

(3) Hong, L.; Tanaka, H.; Ogawa, T. J. Mat. Chem., C
2013, 1, 1137.

(4) Yokoyama, A.; Kojima, T.; Ohkubo, K.; Fukuzumi, S. Chem. Commun.
2007, 3997.

(5) Okujima, T.; Matsumoto, H.; Mori, S.; Nakae, T.; Takase, M.; Uno, H. Tetrahedron Lett.
2016, 57, 3160.

(6) Shi, Z. H.; Zhou, Y. S.; Zhang, L. J.; Mu, C. C.; Ren, H. Z.; ul Hassan, D.; Yang, D.; Asif, H. M. RSC Adv.
2014, 4, 50277.

Figure 1
(Invited) Size Controlled Silicon Quantum Dots: A Model System for Understanding the Physics of Indirect Quantum Dots
Authors: Gutsch Sebastian , López-Vidrier Julian , Hiller Daniel , Zacharias Margit
Published: February 2020

The fabrication of SiOx/SiO2 superlattices combined with thermal annealing enables the size and density control of Si quantum dots [1]. The layered-arranged Si nanocrystals represent a model system to systematically study the photonic and electronic properties of (indirect bandgap) quantum dots prepared in a CMOS compatible way. Hence, the size controlled nanocrystals are used to understand the interplay of absorption and recombination, the carrier kinetics and the electronic transport properties for matrix embedded Si quantum dots. Starting with the temperature dependence of the size depending band gap [2] we will discuss the interplay of radiative and non-radiative recombination for high quantum yield [3-5]. Doping of quantum dots and the respective experimental techniques for its quantification is at the very limit of the nowadays experimental possibilities. We will present systematic doping experiments with P and B which will be analyzed for doping efficiency, in-cooperation into the Si QDs and self-purification effects [6, 7].

[1] M. Zacharias et al. Appl. Phys. Lett. 80 (2002) 661.

[2] A. M. Hartel et al. Phys. Rev. B 85, 165306 (2012).

[3] A.M. Hartel et al. Rev. B 87, 035428 (2013).

[4] J. Valenta et al J. Appl. Phys. 122 144303 (2017)

[5] M. Greben et al. Beilstein J. Nanotechnol. 8, 2315 (2017).

[6] D. Hiller et al. Scientific Reports 7, 863 (2017).

[7] D. Hiller et al. Scientific Reports 7, 8337 (2017).
(Invited) Light Emitting Nanomaterials with Light Detection, Biosensing and Memristive Properties
Authors: Garrido Blas
Published: February 2020

In this talk I will present our latest activities in the field of nanomaterials for integrated optoelectronics with emphasis on the best candidates for convergence with light detection (solar cells), biosensing and resistive memories (memristors). I will first address nanomaterials and basic devices for optoelectronics, which we believe are the basis and the core for solving many new societal challenges. Silicon nanocrystals (Si-nc) in the form of superlattices can be used for fabricating tandem solar cells with improved efficiency over silicon ones. At the same time, Si-nc embedded in dielectrics are routinely used as low-power light emitters with good possibilities for integration with silicon technology. More exotic combinations like for instance i) Multilayered nanostructures with Al and rare earths sandwiched between SiO2 walls and ii) Quaternary compounds with variable composition such as SiAlON, have shown amazing properties aiming at light emission in the visible, and have also demonstrated behavior as memory resistors (memristors). In the field of biosensing, we have recently shown that we can take advantage of nanostructured ITO electrodes for general purpose amperometric biosensors. Finally, we will also show that ZnO based materials in the form of layers and/or quantum dot/wires can be used for convergence as they demonstrate in elemental devices light emission, light detection, biosensing and memristive properties.
Versatile Duplex Electrochemical Sensor for the Detection of CO2 and Relative Humidity Using Room Temperature Ionic Liquid
Authors: Bhide Ashlesha , Jagannath Badrinath , Graef Edward , Prasad Shalini
Published: February 2020

In this work, we present a versatile and a robust electrochemical duplex sensor for detection of CO2 and humidity using a novel sensing material – Room temperature ionic liquid (RTIL). Rising environmental concerns have led to the development of sensors to monitor environmental conditions such as CO2, VOC's, particulate matter, temperature, and relative humidity. Requirement of sensor performance metrics such as low power, high stability, increased sensitivity has led to the investigation of RTIL as a suitable candidate for the CO2 and humidity sensing for usability in a broad range of applications from air quality monitoring in HVAC systems, weather prediction, and monitoring the environment in green houses. RTIL's are essentially solvent free electrolytes consisting of an organic cations and inorganic anions with tunable chemical and physical properties for sensing. The innovation of this study is to interface RTIL's with a metal electrode sensing platform which results in the formation of multi stack electrochemical double layer (EDL). CO2 or water molecules settle within the interstitial spaces formed between the RTIL moieties on the application of a bias potential. AC perturbation of the system causes charge redistribution in the EDL as a result of CO2 or water adsorption which is studied through an AC based technique- Electrochemical impedance spectroscopy (EIS). The frequency response of the EDL provides an insight of the impedance changes of the EDL as the environment changes around them.

We investigated the effects of ambient and elevated CO2 concentrations across a temperature range of 25- 65°C at 45% humidity on two fluorinated RTIL’s- EMIM[TF2N] and EMIM[FAP]. Performance comparison was based on the impedance response and dynamic behavior of the system based on the changes in the anionic symmetry. Both, EMIM[TF2N] and EMIM[FAP] behave similarly but EMIM[TF2N] shows a higher sensitivity to CO2 across temperatures. We also report the effect of varying humidity from 25% to 65% across temperature range of 25- 65°C on the performance of a non-fluorinated RTIL- MMIM[MeSO4]. MMIM[MeSO4] shows a larger change in impedance response with increasing humidity percentages at elevated temperatures. RTIL’s have the potential to be integrated with semiconductor technology for the sensitive detection of CO2 concentrations and humidity ranges across varying temperatures. Our work demonstrates the potential of a new strategy for achieving low power environmental sensors.
(Invited) On-Colloid Lithography: Surface Chemistry Guided Metal Deposition in Hotspots
Authors: Millstone Jill E.
Published: February 2020

We present the use of nanoparticle surface chemistry to mediate the deposition of metals onto colloidal nanoparticle substrates in patterns that are controlled by a supramolecular assembly on the colloid itself. These assemblies may be tuned either by ligand functionality or driven to phase transitions via electrochemical approaches. The solvent facing portion of these assemblies may also act as a selection agent in recruiting specific metals to the existing colloid surface. Combining these properties, we show several deposition motifs as well as broad metal generality using this surface chemistry based approach. We characterize this process and the resulting nanoparticle products using a combination of scanning probe microscopy, electorn microscopy, and nuclear magnetic resonance spectroscopy techniques. Applications in subsequent photomediated chemical processes will also be discussed.
(Invited) Superconformal Filling of through Glass Holes for Application in Glass Interposers
Authors: Dimitrov Nikolay
Published: February 2020

Copper superconformal filling of through glass Holes (TGH) of aspect ratios (AR) 6 and 10 with the use of the additives Tetranitro Blue Tetrazolium Chloride (TNBT), Nitro Tetrazolium Blue Chloride (NTBC), and Thiazolyl Blue Tetrazolium Bromide (MTT) is presented and comparatively discussed as focal point of interest in the development of glass-interposer technologies. The presentation introduces firstly the challenge associated with initial glass metallization and describes briefly the developed by our group “hybrid” method as one of the feasible solutions for coating the glass surface with a continuous and conductive "commoning" layer. Next, the discussion proceeds with consideration of the proposed by W.P. Dow et al “butterfly” mechanism for nucleation of a plug in the center of the TGH to be filled with electrodeposited copper. Different experimental scenarios resulting in the formation hemispherical or X-shaped Cu nuclei that seed the success of the entire superconformal deposition process are also described in this section. The presentation then continues with a critical comparison of the use of all three additives of interest for achieving best results in implementing the superconformal growth mode. Main point of emphasis in that part is the use of MTT for achieving of fastest Cu growth rates. These are manifested by greatly reduced TGH filling times of about 1h and 4h for AR 6 and 10, respectively, compared to about 3h and 12h, respectively, as best results when TNBT and NTBC are tested as additives. In specifying the experimental details,, it is mentioned that constant current electroplating is carried out in the presence of the additives in acidic (pH 2 to 4) copper sulfate or methane sulfonate formulations containing also Cl- ions. In the best plating conditions achieved by the use of MTT, Cu plugs are nucleated in the TGH’s centers while keeping the thickness on external surfaces low. Plugs are formed in AR 6 TGH in as little as 12 min, after which the plating can be viewed as the filling of double-sided blind vias. Issues with imperfections trapped in the plugs have been addressed by decreasing the current around the time of plug formation, then increasing it for the rest of the process. In addition it is specified that the filling of AR 10 holes takes much longer times at lower current density are needed. It is also shown that larger diameter AR 4 TGH have been also successfully filled with Cu. At the end of the presentation a glimpse is made into the reduction behavior of the additives of interest to this work. Also in the conclusive part a cost analysis is presented to show that lab scale quantities of MTT are 8 to 14 times less expensive than the competing additives NTBC and TNBT, respectively.
A Deeper Look at Bottom-up Copper Deposition in High Aspect Ratio through Silicon Vias
Authors: Josell Daniel , Silva Manoj , Kildon Jonah , Moffat Thomas P.
Published: February 2020

Superconformal copper electrodeposition in larger features, as in smaller features, is influenced by both suppressor and chloride in the copper electrolyte. Different behaviors are observed in electroanalytical measurements of low and high chloride electrolytes. One significant difference is the dependence of suppression breakdown and associated S-shaped negative differential resistance (S-NDR) on transport assessed using a rotating disk electrode. Superconformal filling of 56 μm tall, annular Through Silicon Vias (TSVs) from the electrolytes can exhibit the bottom-up evolution previously noted for the Cu system as well as transient or steady-state passivation breakdown along the TSV sidewall, with uniform deposition below, previously demonstrated with Au, Ni and Co S-NDR systems. As both filling geometries are predicted by S-NDR based models, I will discuss the factors that we believe determine the experimental filling geometry.
Cupric Oxide Thin Films for Optoelectronic Application
Authors: Kumar Sanjay , Saralch Sudhir , Pathak Dinesh
Published: February 2020

Copper oxide is a semiconductor that has been studied for several reasons such as the natural abundance of starting material copper (Cu); the easiness of production by Cu oxidation; their non-toxic nature and the reasonably good electrical and optical properties. Copper oxide is well-known as cuprite oxide. The cuprite is p-type semiconductors having band gap energy of 1.21 to 1.51 eV. As a p-type semiconductor, conduction arises from the presence of holes in the valence band (VB) due to doping/annealing. CuO is attractive as a selective solar absorber since it has high solar absorbency and a low thermal emittance. CuO is very promising candidate for solar cell applications as it is a suitable material for photovoltaic energy conversion. It has been demonstrated that the dip technique can be used to deposit CuO films in a simple manner using metallic chlorides (CuCl2.2H2O) as a starting material. Copper oxide films are prepared using a methanolic solution of cupric chloride (CuCl2.2H2O) at three baking temperatures. We made three samples, after heating which convert in black colour. XRD data confirm that the films are of CuO phases at a particular temperature. The optical band gap of the CuO films calculated from optical absorption measurements is 1.90 eV which is quite comparable with the reported value. Dip technique is a very simple and low-cost method, which requires no sophisticated specialized setup. Coating of the substrate of a large surface area can be easily obtained by this technique compared to that in physical evaporation techniques and spray pyrolysis. Another advantage of the dip technique is that it is very easy to coat both sides of the substrate instead of only one and to deposit otherwise inaccessible surfaces. This method is well suited for applying coating on the inner and outer surfaces of tubes of various diameters and shapes. The main advantage of the dip coating method lies in the fact that it is possible to deposit a variety of layers having good homogeneity and mechanical and chemical stability with a very simple setup. In this paper the CuO thin films preparation by dip coating method and their characterization will be presented.
Electrodeposition of Nickel Nanostructures from Deep Eutectic Solvent / Water Mixtures
Authors: Mernissi Cherigui El Amine , Sentosun Kadir , Bals Sara , Terryn Herman , Ustarroz Jon
Published: February 2020

Supported nickel nanoparticles (NPs) are widely used as catalysts for fuel cells and electrosynthesis, as well as for biosensors and supercapacitors. These nanomaterials can be fabricated by multiple methods. However, electrodeposition offers several advantages since it permits the growth of the NPs directly on the support of interest and allows obtaining highly electroactive nanostructures [1]. In order to produce highly electroactive nanostructures, the electrochemical processes on the nanoscale need to be understood. In this context, Deep Eutectic Solvents (DESs) have generated great enthusiasm as a new generation of non-aqueous electrolytes. They offer plenty of advantages compared to traditional aqueous electrolytes or to highly expensive ionic liquids [2]. Moreover, by adding water to the DESs, the electrolyte behavior could be remarkably different. The ability of understanding the effect (and controlling the amount) of water in DES has been proven essential to tune the chemical nature of the electrodeposited Ni nanostructures, thereby obtaining highly electroactive NPs for a wide range of applications [3-4].

The electrodeposition of nickel nanostructures on glassy carbon was investigated in 1:2 choline chloride – urea (1:2 ChCl-U) DES containing different amounts of added water. By combining electrochemical techniques, with ex-situ FE-SEM, XPS, HAADF-STEM and EDX, the electrochemical processes occurring during nickel deposition and the effect of added water were better understood. At highly negative potentials, Ni growth is halted due to water splitting and the formation of a mixed layer of Ni/Ni(OH)2(ads) [3]. Moreover, under certain conditions, the choline cations can also be (electro)chemically reduced at the electrode surface, blocking further 3D growth of the Ni NPs. Hence, a 2D crystalline Ni network can be formed in the inter-particle region, as depicted in the figure [5].

These novel nickel nanostructures can be of great interest for their electrocatalytic activity for different processes, such as the oxygen evolution reaction (OER).

References:

G-R. Li, H. Xu, X-F. Lu, J-X. Feng, Y-X. Tong, C-Y. Su. Nanoscale, 5 (2013) 4056-4069.

E.L. Smith, A.P. Abbott, K.S. Ryder. Chemical Reviews, 114 (2014) 11060–11082.

E.A. Mernissi Cherigui, K. Sentosun, P. Boockenooge, H. Vanrompay, S. Bals, H. Terryn, J. Ustarroz. The Journal of Physical Chemistry C, 121 (2017) 9337-9347.

C. Du, B. Zhao, X-B. Chen, N. Birbilis, H. Yang. Scientific Reports, 6 (2016) 29225.

E.A. Mernissi Cherigui, K. Sentosun, S. Bals, H. Terryn, J. Ustarroz. Manuscript in preparation (2017).

Figure 1
Comparison Study of Different Types of Porous Electrodes in Redox Flow Batteries
Authors: Zhou Xuelong , Wu Qixing , Lv Yunhui , Lin Liyu , Li Xiangyang
Published: February 2020

Redox flow batteries (RFBs), which combines the attributes of fuel cells and solid-state batteries, have been recognized as one of leading technologies for storing electricity that generated from solar and wind farms due to the striking advantages, including excellent scalability, high efficiency, long lifetime as well as high safety [1]. Despite the attractive merits, the widespread deployment of this type of technology was significantly limited by technical and economical issues, such as low power density, high capacity decay rate, low energy density and high capital cost [2]. To address these issues, electrode and membrane designs are of great importance. For instance, electrode design over porous structure and surface properties is critically important for improving the power density and lowering the capital cost. With regard to the electrode design and selection, several types of carbon-fiber based electrodes, such as graphite/carbon felt, carbon paper and carbon cloth, have been employed as the electrodes of RFBs and associated pretreatment procedures have also been investigated, demonstrating decent performance in different RFB systems [3]. However, comprehensive comparison studies on these porous electrodes in RFBs are scarce. In this presentation, we will offer a comprehensive comparison between the state of art RFB electrodes (carbon felt, carbon paper, carbon cloth) in terms of macro and micro porous structure, surface properties, transport properties (hydraulic permeability, mass transfer coefficients, MacMullin number) as well as electrochemical performance. Besides, the use of some novel electrodes, such as brush structured carbon materials, in RFBs will also be disclosed in the present work. With the present comprehensive comparison study, insights on future electrode design and engineering direction will be discussed at last.

[1] A.Z. Weber, M.M. Mench, J.P. Meyers, P.N. Ross, J.T. Gostick, Q. Liu, J.Appl.Electrochem. 41 (2011) 1137-1164.

[2] M.L. Perry, A.Z. Weber, J.Electrochem.Soc. 163 (2016) A5064-A5067.

[3] B.R. Chalamala, T. Soundappan, G.R. Fisher, M.R. Anstey, V.V. Viswanathan, M.L. Perry, Proc IEEE. 102 (2014) 976-999.
Optimally Engineered Flow-Through Electrodes Using Automatic Design Algorithms and Additive Manufacturing
Authors: Beck Victor A , Weisgraber Todd H , Ivanovskaya Anna N , Chandrasekaran Swetha , Moran Bryan D , Watts Seth E , Tortorelli Dan A , Duoss Eric B , Biener Juergen , Stadermann Michael , Worsley Marcus A.
Published: February 2020

Flow batteries are a promising technology for large scale energy storage and load balancing from intermittent power sources, but their viability hinges on our ability to attain high-power outputs while minimizing costs and meeting performance constraints. Effective engineering of these systems is further complicated by limitations on the control of the electrochemical cell component morphologies across scales. At Lawrence Livermore National Lab, we have pioneered a potential solution to this problem using additive manufacturing techniques which enable hierarchical structures controlled from the sub-micron through the centimeter length scales. Yet, even with this expanded design space, the complexity and tight coupling of the underlying physical processes remains as an obstacle to effective design: Apparently obvious choices can nevertheless lead to an unexpected adverse performance impact. To address this challenge, we present an automatic design methodology to optimize the electrode topology over precisely defined performance criteria. We combine forward physics solvers for the full electrochemical problem with gradient optimization code to optimize over multiple objectives simultaneously (e.g., maximizing current, minimizing pressure drop, minimizing material usage, etc.). Our algorithms compute optimal electrochemical cell geometries which are then physically manufactured using additive manufacturing techniques (e.g., direct ink write and projection micro-stereo lithography) and post-processed to create carbon electrodes. We compare the predicted performance of the designs against the experimentally measured performance of the manufactured devices. Our work provides a systematic path toward rational design of cost-effective, high-power flow batteries.
Strategies to Enhance the Performance of Polybenzimidazole Membrane Based Vanadium Redox Flow Batteries
Authors: Maurya Sandip , Park Eun Joo , Kim Yu Seung , Mukundan Rangachary
Published: February 2020

Research on renewable energy sources such as solar and wind has dramatically dropped the cost of electricity generated from these sources. Renewables such as solar photovoltaics, wind turbines and geothermal are producing more and more electricity than ever before.1 Yet, being intermittent in nature prevents the use of such renewables as the main source for grid-scale electricity unless combined with an appropriate electrochemical energy storage (EES). Vanadium flow batteries (VFBs) are preferred choice as EES due to their elongated life cycle, quick response, ability to go for deep discharge, low cost, and independent energy-power outputs.2 However, most VFBs operate at low power densities, which increase the stack size significantly. In addition, costly Nafion® membrane is a key component regarding the high stack cost3; therefore, low power densities significantly increase the cost per kWh capacity. There are reports with improved power densities by modifying cell architecture4; still there is scope for cost reduction by replacing Nafion® completely with low-cost polybenzimidazole (PBI) membranes. PBI membrane has enticed attention thanks to its amphoteric properties, which repel vanadium ions in acid solutions.2 However, due to its high resistance, morphology and chemical structure of the membrane need to be tuned to achieve high power densities.

We report the strategies to tune the PBI membrane properties including acid treatment and thickness reduction. The objectives of these treatments are to improve the proton – sulfate ion transport while keeping permeability of vanadium ions low. Our preliminary results indicate that PBI membranes are capable of operating at higher power densities, if the transport properties and morphology are fine-tuned. Indeed, acid treated PBI membrane showed >550 mWcm-2 of peak power density, which is comparable to that of Nafion® membranes. Furthermore, the capacity decay and long term cycling performance of these PBI membranes in VFBs will be presented at the conference. To the best knowledge of the authors, this is the first instance to report the high peak power densities for PBI membranes in VFBs.

Acknowledgement

This work is supported by Laboratory Directed Research & Development, Los Alamos National Laboratory.

References:

(1) EIA - Electricity Data https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_1_01_a (accessed Nov 16, 2017).

(2) Maurya, S.; Shin, S.-H.; Lee, J.-Y.; Kim, Y.; Moon, S.-H. RSC Adv.
2016, 6 (7), 5198–5204.

(3) Minke, C.; Turek, T. J. Power Sources
2015, 286 (Supplement C), 247–257.

(4) Aaron, D. S.; Liu, Q.; Tang, Z.; Grim, G. M.; Papandrew, A. B.; Turhan, A.; Zawodzinski, T. A.; Mench, M. M. J. Power Sources
2012, 206, 450–453.
Advanced Bi-Additive Vanadium Electrolyte
Authors: Nie Zimin , Wang Wei , Murugesan Vijayakumar , Wei Xiaoliang , Li Bin , Liu Jun , Sprenkle Vincent
Published: February 2020

New all vanadium with bi-additive electrolyte has 30% higher energy density and 80% wider temperature window which will be a promising energy storage option for the future grid. The solubility of the vanadium ions was improved to 2.0M, in a much wider temperature range from -5 to 50⁰C.

Our new bi-additive system containing (NH4)2HPO4 increases the V5+ intermolecular distance from ~5 angstrom to ~8 angstrom which has greatly improved the V5+ electrolyte stability and solubility. Based on the computer simulation results, two V5+ molecular will form complex with one HPO4 which will significantly increase the distance between the two V5+ molecular.

. With the new vanadium electrolyte, we demonstrated both on-line charge/discharge cycling and off-line static electrolyte stability study of at 2.0M vanadium concentration at -5 and 50⁰C. The new additive-assisted vanadium electrolyte provides a revolutionary solution to boost the VRB’s performance, stability, and cost to a whole new level.
On Extending Cycle-Life of the Soluble Lead Redox Flow Battery
Authors: Suman Rathod , Ravikumar Musuwathi Krishnamoorthy , Jaiswal Nandini , Patil Satish , Shukla Ashok Kumar
Published: February 2020

Cycle-life of the soluble lead redox flow battery (SLRFB) is limited due to the oxygen evolution reaction taking place at its cathode. This parasitic reaction leads to imbalanced deposition of lead metal at anode and PbO2 particles at cathode. As a result, the concentration of Pb2+ ions decreases in the electrolyte during repeated charge and discharge cycles leading to formation of sludge containing Pb and PbO2. In this study, we have developed and demonstrated a method of using a bi-functional auxiliary gas-diffusion electrode to mitigate these problems that consequently helps extending cycle life of the SLRFB. The auxiliary gas-diffusion electrode is operated either as an (a) air electrode or (b) a hydrogen electrode. When the auxiliary gas-diffusion electrode is an air electrode, it is used as positive electrode and on coupling with anode of the SLRFB, it forms a galvanic Pb – air cell that on discharge results in dissolving Pb particles. When auxiliary gas-diffusion electrode is a hydrogen electrode, it acts as negative electrode and on coupling with the cathode of the SLRFB forms a galvanic PbO2-H2 cell which on discharge dissolves the PbO2 particles. A novel insight on extending the performance of the SLRFB will be discussed.
Electrochemical Stability and Reversibility upon Cycling of Aqueous Polysulfide Electrodes Beyond the Solubility Limit
Authors: Pan Menghsuan Sam , Su Liang , Jing Linda Wei , Eiler Stephanie L. , Chiang Yet-Ming
Published: February 2020

The low cost, high solubility, and high specific capacity of aqueous polysulfide electrodes are attractive in battery applications. Our group recently developed a redox flow battery system that used an air (oxygen) cathode and an aqueous polysulfide anode, aiming at low-cost large scale grid storage[1]. Surprisingly, for low cost electrochemically active materials such as aqueous polysulfide, the cost of auxiliary components including the supporting electrolytes and the tanks is ~2 times that of the active materials themselves. Accordingly, to further decrease the energy cost, it is imperative to increase the volumetric capacity (Ah/L) of aqueous polysulfide electrolytes.

One natural way to increase the capacity of the redox active solution is to increase the “effective” concentration of the active species, which is bounded by the solubility of the active species. However, the solubility of aqueous polysulfides in the reduced form (Na2S2) at room temperature is ~2.5M (5M total sulfur), equivalent to 67 Ah/L when utilizing capacity range between Na2S2 and Na2S4. One strategy to overcome this limitation is to leverage the redox activity of the precipitated polysulfide hydrate (Na2S2 xH2O) during the reduction reaction, which subsequently can be oxidized to the fully soluble higher-order polysulfide (Na2S4). Using this approach, we doubled the capacity to 134 Ah/L by using 10M total sulfur in the reversible cycling between Na2S2 and Na2S4. Long-term stability of this “precipitation-solution” conversion is studied using galvanostatic cycling for more than 1600 hours. In addition, XPS and SEM are utilized to measure the overall oxidation state of the precipitates and to understand the fast dissolution of the polysulfide hydrate. The overall oxidation state of the precipitates is particularly important in inferring the stability of the polysulfide species remained in the solution as the overall nominal solution composition needs to remain between Na2S2 to Na2S4 to avoid capacity fading associated with chemical decays. Furthermore, aqueous polysulfide using carbon suspension electrodes is demonstrated to alleviate large overpotential associated with insulating precipitate formation.

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.

[1] Li et al., Joule
1, 306-327 (2017).
Dissolution Induced Self-Selective Zn- and Ru-Doped TiO2 Structure for Electrochemical Generation of KClO3
Authors: Pala Raj Ganesh , Kishor Koshal , Saha Sulay
Published: February 2020

We demonstrate an electrochemical approach to prepare a highly active and stable (Zn, Ru)-doped TiO2 (Ru0.26Ti0.73Zn0.01Ox) for electrochemical generation of KClO3. The essential ingredients of this approach consists of (1) co-electrodeposition of Ru, Ti and Zn as metallic alloy and then annealing it to oxide (2) dissolution under electrochemically oxidative acidic environment of Ru and Zn-rich surface clusters having high selectivity towards oxygen evolution reaction (OER) leaving Ti-enriched structure that is more selective to chlorine evolution reaction (CER) and (3) using this electrocatalyst for KClO3 production under near-neutral pH conditions. Dissolution of Ru- and Zn enriched surfaces result in porous structure with higher electrochemical surface area and roughness. Furthermore, this electrochemical dissolution of (Zn, Ru)-rich surface results in electrocatalytic structure that is self-selective towards KClO3 formation with higher specific activity. The co-electrodeposition of Zn aids (1) the formation of roughened and porous surface structure through surface dissolution of Zn- or ZnO clusters and (2) the enhancement of conductivity of electrocatalyst through formation of oxygen vacancies. The obtained structure has been found to show higher specific activity, activity and stability towards KClO3 production in comparison to untreated (Zn, Ru)-doped TiO2 or Ru-doped TiO2 or RuO2.
Pressure Influence on Acoustic Cavitation Phenomenonin Ionic Liquids: Electrochemical Study
Authors: Naidji Bouzid , Hallez Loic , Et Taouil Abdeslam , Rebetez Michel , Hihn Jean-Yves
Published: February 2020

The propagation of an acoustic wave into a solution can lead to the break of liquid cohesion strengths. This results in the nucleation, growth and collapse of cavitation bubbles feed by solvent vapors and dissolved gases. This collapse may be beneficial as in the case of cleaning processing, but is clearly detrimental in some application as in the case of therapeutic treatments such as tumor ablation, or for the ultrasonic power transmission in coupling fluids. For the electrochemical processes assisted by ultrasound, its control is mandatory. Then, this phenomenon must be reduced by the application of over-pressures into the reactors [1].

To be able to determine the respective contributions of dissolved gases and of vapors into the cavitation bubble collapse, the present work will seek the effect of a limitation in dissolved gases into a sonoreactor by controlling the pressure in a low vapor pressure media: ionic liquids. Those solvents are constituted of a dissymmetric anion and cation, are liquid at room temperature, and show excellent properties for our tests such as a great conductivity. As their vapor pressure is exceptionally low, only the dissolved gases will contribute to the cavitation: as the content in dissolved gas is driven by the pressure, its reduction will result in a reduction of the cavitation activity.

In order to quantify this level, the diffusion study of electrochemical species was used as mass transfer sensor [2]. An electroactive species (Ferrocene) forming a rapid and reversible system is present in the solution at low concentration, and in presence of ultrasound, two contribution to the current in steady state conditions can be observed: one depending of the time and the other independent. Both are respectively proportional to the flow generated by the acoustic convection and to the bubble collapse at the electrode interface. The results show an important decrease of the cavitation phenomenon for argon pressure lower than 0.6 bar. A mathematical treatment of the curves allows the extrapolation up to the absolute cavitation quenching, at which the single contribution comes from convection.

[1] Parag R. Gogate, Aniruddha B. Pandit. 2005, Ultrasonic Sonochemistry , 12 , 21_27.

[2] Pollet B.G.,Hihn J-Y.,Doche M.L., Mandroyan A., Lorimer J-P., Mason T.J. 2007 , Journal of Electrochemistry Society, 154 , 131-138.

Figure 1
A Machine Learning Based Computational Protocol for Rapid Screening of Carbon Based Materials for Lithium Ion Battery Applications
Authors: Jang Seung Soon , Sood Parveen
Published: February 2020

Carbon based materials have been explored for cathode applications in Lithium ion batteries because of their low environmental impact, easy availability of carbon and the rich chemistry of carbon based compounds which allows their properties to be tailored using functionalization and doping. Prototype devices based on carbon nanotubes and graphene which show superior combination of energy and power density have already been demonstrated. The calculation of redox potentials using DFT method to search for promising materials, is a time and resource expensive methodology. Consequently, correlations between redox potentials and electronic properties such as HOMO, LUMO and electron affinity are being explored so as to identify promising materials based on electronic properties which are relatively easily calculated. For DFT based computations of redox potentials, implicit solvent models such as Poisson-Boltzmann solver are used to compute solvation effects, at a reference temperature. The dielectric constant and probe radius of the solvent are inputs for solvation energy calculations. In this work, we intend to train a supervised machine learning algorithm, based on the structures in a given class of material, and investigate if a sophisticated machine learning based model can be used to predict redox potentials based on electronic properties from DFT calculations. It is anticipated that a machine learning model can be used as a rapid screening tool for identifying and designing novel carbon based materials for redox applications.
The Analytical Transport Network Model for Diffusive-Reactive Flow in 3-D Microstructural Networks: A Computationally Economical Model for Potential Use in Multi-Scale Modeling Efforts
Authors: Cocco Alex P. , Nakajo Arata , Grew Kyle N. , Chiu Wilson K. S.
Published: February 2020

Electrochemical energy materials are those used in electrochemical energy conversion and storage technologies, such as batteries, fuel cells, and electrochemical capacitors. Their development is complicated by the fact that they must simultaneously satisfy a diverse set of design criteria, which in turn depend on multiple, interacting physical processes occurring across multiple length and time scales.

An energy material’s microstructure adds to its complexity: in addition to occurring across multiple length and time scales, the physical processes that determine its performance also occur within a geometrically complex, often 3-D, domain. Then, if one wishes to integrate molecular-scale knowledge (e.g., from molecular dynamics simulations, etc.) into a multi-scale design framework, it would be advantageous to have a robust, computationally inexpensive means of accounting for the geometrical complexity of a typical energy material microstructure.

In this work, we consider energy material microstructures comprised of interwoven, 3-D networks and present a heuristic, fully analytical model – the Analytical Transport Network (ATN) Model – that explicitly relates the morphology and topology of a given network’s channels to its effective transport coefficient and, in an approximate manner, its electrochemical activity.

ATN’s effective transport coefficient estimates obtained for conserved flow within a set of artificially-generated and real energy material microstructures exhibited good agreement with those obtained from electrochemical fin theory and finite element analysis, but were computed 1.5 and 6 orders of magnitude faster, respectively. In addition, the theory explicitly relates a number of morphological and topological parameters directly to the effective transport coefficient, whereby the distributions that characterize the structure are readily available for, e.g., morphological/topological optimization studies or further topological characterization by network science. In considering reacting flow, the ATN model is used to identify morphological and topological features that influence the flow consumed by reactions per the flow entering the network.

In this talk, we will present the ATN model, compare its predictions to those from existing techniques as well as to experimental measurements, and discuss how it can potentially be extended to elucidate the influence of channel morphology and topology on multi-component and transient flow.
Quantum-Continuum Simulations of High Power Density Oxide Electrodes for Pseudocapacitive Energy Storage
Authors: Keilbart Nathan D. , Okada Yasuaki , Higai Shinichi , Dabo Ismaila
Published: February 2020

Pseudocapacitors are energy-storage devices characterized by fast and reversible redox reactions near the surface of an electrode that allows them to store large amounts of energy at fast rates [1]. Much is unknown about these materials due to the complex electrochemical reaction that occurs at the interface between the electrode and solvent. A theoretical modeling approach is developed focusing on ruthenium dioxide (RuO2), a prototypical pseudocapacitive electrode material, for analyzing the electrochemical response of an electrode under realistic conditions in order to identify the factors that control the performance. Electronic-structure methods are used in combination with a self-consistent continuum solvation model to generate a complete dataset of free energies for varying amounts of proton coverage on the surface. The dataset is used in conjunction with a grand-canonical Monte Carlo sampling technique that computes hydrogen-adsorption isotherms and the charge-voltage response of the system. Close agreement is found with experimental results of the RuO2 (110) surface under optimal surface charging conditions [2]. It is found that the intrinsic double-layer contribution represents a small fraction of the overall electrochemical response of the electrode but controls to a large extent the onset of pseudocapacitive reactions by influencing the change in the surface dipole. At variance with RuO2 (110), the double-layer capacitance of RuO2 (100) is found to vary linearly across a significant portion of the voltage range. This range of variation is also well captured by first-principles calculations of the double-layer capacitance for different coverages. The newly developed model provides a widely applicable computational method to help identify novel pseudocapacitive materials.

[1] V. Augustyn. P. Simon, and B. Dunn, Energy and Environ. Sci.
7, 1597 (2014)

[2] N. Keilbart, Y. Okada, A. Feehan, S. Higai, and I. Dabo, Phys. Rev. B
95, 115423 (2017)