bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and Electrochemical Properties of Nb2O5-Ge/GeO2 Core-Shell Structure for Reversible Lithium Storage
Authors: Kim Kyungbae , Kim Jae-Hun
Published: February 2020

Group IV element-based nanostructures have been actively investigated as high-capacity anodes for Li-ion batteries. Among them, germanium (Ge)-based materials become newly promising because it shows a high theoretical capacity (ca. 1600 mAh·g-1) and faster Li transport properties compared to the other materials in the same group. However, the long-term cycling stability is still a challenging issue, which is resulted from volume expansion during cycling. To overcome the limitation, the way to maintain stable structures against the volume changes of Ge should be considered.

This study proposes a new Ge-based structure by incorporating Nb2O5, which is stable during Li insertion and extraction processes. An Nb2O5 nanoparticle core-Ge/GeO2 shell structure material was prepared by a simple hydrothermal method and the following heat-treatment. First, a microscale NbOx-GeOx precursor was synthesized by the hydrothermal process with copolymer producing core-shell structure. Subsequently, it was heat-treated to obtain pyrolysis of copolymer and to form a reduced Ge/GeO2 thin shell on the nanoscale Nb2O5 core structure without additional carbon sources. Electrochemical test results exhibited that the synthesized electrode materials had a high reversible capacity of 700 mAh·g-1 after 100 cycles with an initial coulombic efficiency of 74%. In the long-term cycling test with a high rate, it exhibited an excellent cycling stability with a capacity retention ratio of 97% even after 1000 cycles.
Metal Doped Ammonium Vanadium Oxide Cathode with Exceptionally Discharge Capacity for Sodium-Ion Battery Fabrication
Authors: Sarkar Ananta , Mitra Sagar
Published: February 2020

Sodium ion battery, has attracted great attention to the energy storage system for its low cost and uniform abundant resources in the earth crust and also for its similar chemical property to lithium. Basically, sodium-ion has larger ionic size than lithium needs a wider open framework to accumulate the larger ion during the intercalation-deintercalation process. Herein, we demonstrate one-dimension ammonium vanadium oxide (NH4V4O10) material as suitable cathode materials for Na-ion storage. The layered structured ammonium vanadium oxide is prepared by the simple hydrothermal process. The elongation of NH4V4O10 nano-belts towards c-axis and minimum growth towards b-axis i.e., [0k0] results in a faster Na-ion transport and provide a high reversible capacity. Here, we improved the capacity by a metal oxide (Al, Ni, and Zr) doping on NH4V4O10. Among all, zirconium-doped NH4V4O10 showed best electrochemical performance. We further optimized the zirconium doping concentration on NH4V4O10. The best electrochemical performance was obtained by 3.33-mole% zirconium doping on vanadium side of NH4V4O10. The doped Zr- NH4V4O10 showed high discharge capacity of 342 mAh g-1 at 200 mA g-1 current density and even at the higher current rate of 500 mA g-1 current rate it exhibited the high discharge capacity of 185 mAh g-1 with 81 % capacity retention after 50 cycles.
Enhanced Performance of Lithium-Ion Batteries By Conductive ALD Thin Film Coating
Authors: Liang Xinhua , Gao Yan
Published: February 2020

Surface modification has been widely considered as an effective strategy to boost cycle-life and enhance conductivity of electrode particles for lithium ion batteries (LIBs). Atomic layer deposition (ALD) is a layer-by-layer thin film coating technique. Through ALD, a conformal ultrathin coating with controllable thickness can provide initial protection for surface of active materials. Recently, we studied cerium dioxide (CeO2) and iron oxide as conductive coating materials for LIB application. Both CeO2 and iron oxide can significantly enhance the electrochemical performance of LIB electrode materials. For example, iron oxide films were coated on LiMn1.5Ni0.5O4 particles by ALD for the synergetic effect of performance enhancing by iron doping and conformal iron oxide film coating. With an optimal film thickness of ~0.6 nm, the initial capacity improved by 25% at room temperature and by ~26% at 55 °C at a 1C cycling rate. The synergy of doping of LiMn1.5Ni0.5O4 with Fe near surface combined with the conductive and protective nature of the optimal iron oxide film led to high capacity retention (~93% at room temperature and ~91% at 55 °C) even after 1,000 cycles at a 1C cycling rate.
(Invited) Stability and Kinetics of the Li/Solid-State Electrolyte Interface
Authors: Sakamoto Jeff , Sharafi Asma , Wolfenstine Jeff , Taylor Nathan J , Wang Mike , Siegel Donald J , Dasgupta Neil P.
Published: February 2020

While there have been recent advances in solid ion conductors exhibiting conductivities comparable to liquid electrolytes, how to best capitalize on these materials discoveries to enable new energy storage technology is currently not known. Of particular interest is the integration solid-state electrolyte into solid-state batteries; however, numerous questions remain. What are the design rules? How are solid-solid interfaces formed? How does charge transfer occur at interfaces?

Essentially, there are two interfaces of interest in solid-state batteries, distinguished by the electrode type; the alkali metal electrode and the ceramic electrode. Several key scientific challenges related to these two interfaces must be addressed to mature solid-state batteries. This discussion is centered on the alkali metal/solid electrolyte interface. The solid electrolyte based on garnet-type oxide, of nominal composition Li7La3Zr2O12 (LLZO), is used as a model system that simultaneously exhibits fast-ion conductivity and stability against metallic Li.

To date, there are few examples of bulk-scale Li-ion conducting solid electrolytes that are stable at the Li/Li+ redox potential. This paper elucidates stability and kinetics as a function of LLZO composition and surface chemistry. EIS, TEM, and electron spin resonance analysis describes the subtle interaction at the interface between Li metal and LLZO. Simple approaches to achieving negligible Li-LLZO interface resistance (~1 Ohm.cm-2) with no coatings is described. Based on this mechanism, a simple procedure for removing these surface layers is demonstrated, resulting in a dramatic increase in Li wetting and the elimination of nearly all interfacial resistance. Combined, the demonstrated stability and low interfacial resistance suggests a pathway to achieving viable high energy density solid-state batteries enabled by the LLZO-based solid electrolyte.
An Orthogonal Investigation of Sulfur Modified Li2FeSiO4 for Lithium Ion Batteries
Authors: Luo Xiaoying , Wang Pingping , Cheng Xuan , Zhang Ying , Huang Liuying
Published: February 2020

The electrochemical performance of lithium iron silicate (Li2FeSiO4) as a cathode material for lithium ion batteries would be remarkably enhanced by selective substitution of 25% oxygen with 25% sulfur to form a Li2FeSiO3S compound based on the previous first-principles calculation. However, the experimental verification has little studied. In this work, the sol-gel precursor and solid-state reaction route was employed to prepare a series of carbon coated Li2FeSiO4 (Li2FeSiO4/C) composites with different sulfur modifications using 1-dodecanethiol as a sulfur source material. The effects of important preparation parameters including sucrose amount, sulfur content, sintering temperature and sintering time on the crystal structure, surface morphology and electrochemical performance of sulfur modified Li2FeSiO4/C composites were investigated through orthogonal design experiments. The results indicated that the significance of the influence on the capacity performance in decreasing order followed sulfur doping content > carbon content > sintering temperature > sintering time. The optimized synthesis conditions were determined to be carbon content of 50% and sulfur doping content of 20% with the sintering temperature at 650°C for 12 h.
Lithium-Sulfur Batteries: The Effect of High Sulfur Loading on the Electrochemical Performance
Authors: Cha Eunho , Patel Mumukshu D. , Choi Tae Youl , Choi Wonbong
Published: February 2020

It is no secret that sulfur as a cathode material is a promising candidate for next generation Li metal-based batteries. However, the intrinsic limitations associated with low conductivity of sulfur and instability of sulfur based composite prevents the commercialization of lithium sulfur batteries. For the past years of Li-S batteries research, many research has been carried out on the cathode design to improve the electrochemical performance. However, it has been mathematically determined that even with high sulfur loading amount and effective sulfur utilization, the true value of energy density cannot outperform the currently available LIBs. That is, other inactive materials must be utilized to address the inherent sulfur issues which would only add more weight. Thus, we propose a novel and facile synthesis of binder-free three-dimensional carbon nanotubes (3D CNTs)/sulfur (S) hybrid composite as an electrode material, where 3D CNTs provide a high conduction path and short diffusion length for Li-ions, while providing ample amount of space for higher sulfur loading. In addition to sulfur loading, the amount of electrolyte also determines the electrochemical performance of Li-S cell in terms of sulfur utilization and cycling stability. However, the statistical analysis shows that more than 90% of reported publications have neglected this E/S ratio. This is important parameter for determining sulfur utilization and energy density of the cell. Here, we report the performance of three-dimensional carbon nanotubes/sulfur hybrid composite with different sulfur loading amounts from 1 to 9 mg/cm2 while tuning the electrolyte/sulfur (E/S) ratio from 12 to 1. The results have demonstrated the E/S ratio of 7 (60 µL electrolyte to 8.5 mg cm-2 sulfur) with reversible specific capacity of ~1068 mAh g-1 at 0.1C rate (~1.4mA cm-2) for up to 150 cycles.
Controlled Surface Structure and Chemistry with Transition Metal Enrichment for Cathode Materials
Authors: Ahn Juhyeon , OH Si Hyoung , Chung Kyung Yoon , Cho Byung Won
Published: February 2020

Transition metals enrichment on the surface of layered nickel-cobalt-manganese oxide cathodes leads to the structural changes, hindering the facile lithium-ion transportation at the surface of the particles. These inhomogeneous metal distributions and structural evolutions are progressively proceeded with electrochemical cycling from the surface to the bulk, which causes to severe material degradation and short cycle life. In this study, we develop the new surface structure and chemistry on the layered cathode materials to enhance the battery performances by controlling the local concentration of transition metal. Our strategy is to improve the surface instabilities by either suppressing unwanted transition metal segregation or creating an ion conductive oxide phase or both on the specific crystallographic planes for the layered host materials. This is conducted by adding electrochemically inactive transition metals together with the active metals during the synthesis because that the transition metal elements are individually and preferentially enriched to the particular facets such as (20–2), (200), and (001) of the layered bulk. As a result, the unique surface layers are spontaneously formed along the surface planes within a few nanometer. The electrochemical characteristics shows that the newly created surface phases strongly influence on the high rate performance and long cycle life.

This work is supported by the National Research Foundation of Korea (NRF-2011-C1AAA001-0030538).
Modified Ca-Graphite Intercalation Compounds As Anode Material for Li Ion Batteries
Authors: Miyamae Ryohei , Tei Go , Kano Akira
Published: February 2020

Due to the increasing demands for the high capacity lithium ion batteries (LIBs) for use in mobile devices and electric vehicles, a new anode material with a higher capacity than that of graphite (372 mAh/g) is desired. As a candidate of such anode material, alloy-type anode (Si, Ge, Sn, etc.) shows much higher capacity than that of graphite [1]. However, their large volume modification during the charge-discharge process limits their cyclic performances. On the other hand, high capacity carbon based materials, such as graphene sheets, carbon nanotubes and nanofibers have also attracted much attention [1]. For practical use, their high intercalation potential of lithium and the difficulty of mass-production of these materials have to be overcome.

In this study, we report a new type of high capacity carbon based material, Ca0.6-xB1.2C4.8. It is a novel material obtained by one-pot heat-treatment of graphite with boron and calcium sources. Its highly ordered graphite-like layer structure distinguishes it from the former reported high capacity carbon based materials, such as graphene sheets, carbon nanotubes and nanofibers. Its specific capacity was 552 mAh/g, which is much higher than that of graphite. This result suggests the possibility of realizing a yet higher capacities for graphite based materials. The detailed preparation method, characterization, and electrochemical measurements will be discussed on the session.

References

[1] Goriparti et al., J. Power Sources, 257, 421-443 (2014)
High Concentration of LiBr in Electrolyte and Graphene-Polydopamine Composite Layer on Li Metal for High Efficient and Long Term Cycling Li-O2 Batteries
Authors: Kwak Won-Jin , Sun Yang-Kook
Published: February 2020

For advanced applications such as electric vehicles (EV), Li-O2 batteries are considered as a prospective candidate for next-generation to replace conventional Li-ion batteries. However, the catalytic effect of the redox mediator for oxygen evolution gradually deteriorates during repeated cycling owing to its decomposition at the surfaces of both the oxygen electrode (cathode) and the Li metal electrode (anode).1,2 Here, we designed optimized Li-O2 batteries with a continuously effective redox mediator and a stable protective layer for the Li metal electrode by optimizing the LiBr concentration and introducing a graphene–polydopamine composite layer, respectively.3 These synergistic modifications lead to a reduction of the charge potential to below 3.4 V and significantly improved the stability and cycle life of Li–O2 batteries. Consequently, a high energy efficiency of above 80% was maintained over 150 cycles. Herein, we confirmed that the relationships between all the battery materials should be understood in order to improve the performance of Li-O2 batteries.

References

W.-J. Kwak, D. Hirshberg, D. Sharon, H.-J. Shin, M. Arfi, J.-B. Park, A. Garsuch, F. F. Chesneau, A. A. Frimer, D. Aurbach, Y.-K. Sun, Mater. Chem. A
2015, 3, 8855.

W.-J. Kwak, D. Hirshberg, D. Sharon, M. Arfi, A. A. Frimer, H.-G. Jung, D. Aurbach, Y.-K. Sun, Energy Environ. Sci.
2016, 9, 2334.

W.-J. Kwak, S.-J. Park, H.-G. Jung, and Y.-K. Sun, Adv. Energy Mater. 2017, 7, 1702258
High Electrocatalytic Activity of PdCu/C Toward Oxygen Reduction Reaction
Authors: Gong Qing , Gong Shuiping , Cheng Xuan , Zheng Jiwu , Yang Weifeng , Zhang Tengfei , Huang Liuying
Published: February 2020

A series of carbon supported palladium copper alloyed catalysts (PdCu/C) were prepared using different molar ratios of Cu to Pd (Cu/Pd), namely, Cu/Pd=1.0, 2.0, 3.0, 4.0, 4.5, and 5.0, by a facile two-step method. The Cu nanoparticles were obtained by microwave assisted route, and followed by the formation of PdCu/C nanoparticles through galvanic substitution of Pd on Cu nanoparticles. The effects of Cu/Pd ratio on the microstructure and electrocatalytic activity of PdCu/C toward oxygen reduction reaction (ORR) were systematically investigated. The as-prepared PdCu nanoparticles exhibited mainly cubic phase with average crystallite sizes ranging 4.7~6.7 nm by varying the Cu/Pd ratio of 1.0~5.0. The higher alloying degree and better ORR activity could be achieved at Cu/Pd=4.5. The half-wave potential (E1/2) reached 0.760 V in 0.1 mol/L HClO4 solution, which was 40 mV lower than that of commercial Pt/C, with a four-electron transfer pathway toward ORR.
Electrochemical Stability of Pt Nanoparticles Supported on a Wide Library of Carbon Supports, Either Used Bare, or Modified By Fluorination or Tin Oxide Deposits
Authors: Asset Tristan , Ahmad Yasser , Labbé Fabien , Batisse Nicolas , Dubois Marc , Guerin Katia , Berthon-Fabry Sandrine , Metkemeijer Rudolf , Dubau Laetitia , Maillard Frederic , Chatenet Marian
Published: February 2020

Throughout the years, a lot of effort has been devoted to improve the electrochemical activity and stability of Pt-based electrocatalysts for the oxygen reduction reaction (ORR), moving from Pt nanoparticles (NPs, diameter ~ 2 – 3 nm) to complex nanostructured materials (i.e. Pt-based hollow, nanoframes or core@shell nanoparticles 1–3). Most of these nanostructures remain more efficient when supported onto a support, as this results in an enhanced specific surface area and, thus, an enhanced mass activity. As such, the nature and the intrinsic stability of the carbon support cannot be ignored, in particular in terms of durability. Here, we investigated (i) the activity of Pt NPs on different carbon supports (with various degrees of graphitization, specific surface area and surface treatments) and (ii) their stability during load (15,000 step cycles between E = 0.6 V vs. RHE and E = 1.0 V vs. RHE) or start-stop (1,000 step cycles between E = 1.0 V vs. RHE and E = 1.5 V vs. RHE) protocols. To that goal, a combination of complementary experiments (electrochemistry, transmission electron microscopy and Raman spectroscopy) were used. As an example, Figure 1 shows the evolution of the specific activity for the ORR measured at E = 0.95 V vs. RHE before and after the load-cycle ageing procedure.

(1) Dubau, L.; Asset, T.; Chattot, R.; Bonnaud, C.; Vanpeene, V.; Nelayah, J.; Maillard, F. ACS Catal.
2015, 5, 5333–5341.

(2) Chen, C.; Kang, Y.; Huo, Z.; Zhu, Z.; Huang, W.; Xin, H. L.; Snyder, J. D.; Li, D.; Herron, J. A.; Mavrikakis, M.; Chi, M.; More, K. L.; Li, Y.; Markovic, N. M.; Somorjai, G. A.; Yang, P.; Stamenkovic, V. R.; Samorjai, G. A.; Yang, P.; Stamenkovic, V. R.; Somorjai, G. A.; Yang, P.; Stamenkovic, V. R. Science
2014, 343, 1339–1343.

(3) Oezaslan, M.; Hasché, F.; Strasser, P. J. Phys. Chem. Lett.
2013, 4, 3273–3291.

Figure 1
Graphene Oxide Emulsions As a Catalyst Support for Metal Catalysts and Catalyst Layer Preparation: Cutting Corners with Hummer’s Method
Authors: Glass Dean , Galvan Vicente , Prakash G. K. Surya
Published: February 2020

Hummer’s method is a widely-used method for preparing graphene oxide from graphite powder. After the graphite is oxidized and cleaned with hydrochloric acid and water, an aqueous emulsion is formed that usually undergoes a lengthy drying procedure to form a powder. In this study, such emulsions produced were made to undergo various forms of reduction including solvothermal, microwave-based, and electrochemical instead of being dried and redispersed into a solvent. Graphene oxide was also dried in an oven for comparison. The emulsions were also mixed with various metal salts for a one pot reduction. The graphene oxide emulsions were also applied to Toray carbon electrodes and formed a thin film that didn’t penetrate the electrode like various ink solutions normally synthesized for MEA fuel cell applications. Various characterization techniques including XRD, Raman, SEM, and XPS displayed similar characteristics for the graphene oxide emulsion catalysts, both bare and with the metal salts mixed in. Various half-cell testing also displayed similar performances for the graphene oxide emulsion and dried catalysts.
(Invited) Self-Humidifying Ultrathin Proton Conductive Membranes for Low Temperature Hydrogen Fuel Cells
Authors: Gao Ping
Published: February 2020

An ultra-thin proton exchange membrane (PEM) with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on hydrogen and oxygen with 0% relative humidity. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated layered double hydroxide (LDH) nanosheets by chemical vapor deposition (CVD). After embedding Pt-LDHs nanocatalysts in 9 µm thick Nafion membranes, exfoliated LDH nanosheets effectively captured crossovered hydrogen and oxygen through membranes. Meanwhile, Pt nanocatalysts on LDH nanosheets catalyzed reactions between captured hydrogen and oxygen and provided in-situ hydration inside Nafion membranes to maintain theirs proton conductivity level. Furthermore, LDH nanosheets reinforced Nafion membranes with 162% improvement in tensile modulus and 126% improvement in yield strength. In a hydrogen fuel cell running with dry fuels, the MEA employing Pt-LDHs/Nafion membrane showed an improvement of 250 % in maximum power density, an increase of 300 % in current density at 0.3V and an improvement of 900 % in current density at 0.5V as compared to those of the MEA with a commercial Nafion 112 membrane. Furthermore, fuel cell tests were conducted on the PEMs with the thickness of 25 μm to observe the synergic effects of self-humidification and the suppression of fuel crossover. Compared to the commercial Nafion 211 membrane, Pt-LDHs/Nafion membrane with a thickness of 25 μm exhibited a combination of desirable properties for the development of affordable and durable hydrogen fuel cell technology, including better mechanical properties, higher open-circuit voltage (OCV), lower ohmic resistance and enhanced water management in a hydrogen fuel cell without external humidification.
Reinforced Polymer Electrolyte Membrane Development for Membrane Electrode Assembly of PEMFC
Authors: Kim Na Young , Lee Dong-Hoon , Lee Eun-Su , Yum Seung Jib , Park JungHwa , Lee Moo-Seok
Published: February 2020

Recently, proton exchange membrane(PEM) fuel cells have been widely considered as one of alternative devices for energy generation system as a clean and efficient for transportation and many other applications. The PEMFC systems need functionalized polymer as PEM which can transfer protons. The PEM for PEMFC require high proton conductivity, good chemical and mechanical durability. In particular, physical and chemical durability of PEM is important because the operation condition of the fuel cell for automobile needs to be repeatedly humidified and dried and requires high output. We so have introduced a porous substrate into the PEM to prepare reinforced polymer electrolyte membrane that it can stand severe condition. The reinforced PEM has good mechanical stability like dimensional stability and water uptake because the porous support suppresses the volume expansion in the plane direction. So reinforced PEM exhibits enhancement of physical properties and durability than freestanding PEM, but its overall characteristics and performance are affected by the structure of the composite layer. Therefore, in this study, we tried to derive the optimum combination condition of ionomer and support. The results obtained from this study show that the reinforced PEM can ensure physical durability through dimensional stability and its properties depend on the structure of the composite region and the substantial porosity of the substrate.
Impact of Heat Treatment on the Electrochemical Properties of Octahedral Pt-Ni Nanoparticles
Authors: Xiao Fei , Shao Minhua
Published: February 2020

Pt is still the most used catalyst for various electrocatalytic reactions. But its high cost and scarcity hinder its wide application. In order to address this problem, researchers found that alloying Pt with one or more transition metals such as Ni, Fe or Co can enhance its activity via maximizing the exposure of (111) facets.1 Octahedral Pt-Ni nanoparticles have been regarded as promising electrocatalyst for various reactions.2-4 It has been found that post heat annealing on the Pt-Ni octahedra plays a significant role in altering their activity and durability during oxygen reduction reaction.
5

In this study, the structure evolution and compositional segregation were systematically studied during annealing in various atmosphere (vacuum, N2, H2, Ar and air) by XRD, TEM, XPS and electrochemical techniques. The impact of the heat treatment on the activities toward oxygen reduction reaction, hydrogen evolution reaction, and ethanol electro-oxidation reaction were assessed. It is interesting to find that the carbon support might be unstable in certain atmosphere, for example, Ar, and can be deposited on the catalyst surface. Figure 1 compares the CVs of Pt-Ni treated in Ar and N2 at 400 °C with the unannealed one. It is clear that the surface area of Pt-Ni treated in Ar diminished due to carbon coating.

In this talk, the composition and structural evolution result upon annealing will be presented. Their effects on various electrochemical reaction activities will be discussed.

Figure 1. Comparisons of cyclic voltammograms of Pt-Ni annealed in N2 (blue), Ar (red) at 400°C for 30 min, and un-annealed one in an N2-saturated 0.1 M HClO4 solution.

Reference:

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315 (5811), 493-497.

Sulaiman, J. E.; Zhu, S.; Xing, Z.; Chang, Q.; Shao, M. ACS Catalysis
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7 (8), 5134-5141.

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13 (7), 3420-3425.

Kavian, R.; Choi, S.-I.; Park, J.; Liu, T.; Peng, H.-C.; Lu, N.; Wang, J.; Kim, M. J.; Xia, Y.; Lee, S. W. Journal of Materials Chemistry A
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6 (2), 692-695.

Figure 1
Bipolar Polymer Electrolyte Interfaces As Separators for High Performance Direct Borohydride Fuel Cells
Authors: Wang Zhongyang , Parrondo Javier , He Cheng , Sankarasubramanian Shrihari , Ramani Vijay K
Published: February 2020

Direct borohydride fuel cells (DBFCs), operating with NaBH4 as a fuel and H2O2 as the oxidant have attracted a lot of attention due to their high theoretical cell voltages and tactical advantages, particularly for defense-related applications. DBFCs have a high energy density of 9.3 kWh kg-1 and specific capacity of 5.67 kAh kg-1 based on NaBH4 oxidation in alkaline media [1]. Using liquid hydrogen peroxide as the oxidant, the DBFC is a safe and attractive low temperature power source for unmanned underwater vehicles (UUVs) as they exhibit excellent energy and power density, are safe, given the high flash point of NaBH4, and do not release any gaseous effluents, enabling operation at neutral buoyancy[2]. One challenge for this system is the separation between the anolyte fuel (1.5M NaBH4 in 3M KOH) and catholyte oxidant streams (15% H2O2 in 1.5M H2SO4), while another is the high instability of NaBH4 in acidic or even neutral pH. Herein, a bipolar interface membrane electrode assembly is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The bipolar interface employed to separate anolyte and catholyte was based on an anion exchange membrane (AEM) interface in conjunction with a cation exchange membrane (Nafion®) separator. Studies of ion-containing block copolymers have provided clear evidence that the phase separation between hydrophilic and hydrophobic phases can produce materials with excellent ionic conductivity [3, 4]. The DBFC with the bipolar interfaces yielded a promising peak power density of 300 mW cm-2 in a 5-cm2 active area cell. Different operating conditions such as catalyst loading, operation temperature, flow rate and thickness of separator were investigated. The bipolar junction offers improved performance in the DBFC when compared with the use of a typical AEM or PEM configuration in the MEA.

References

[1] J. Milikić, G. Ćirić-Marjanović, S. Mentus, D.M.F. Santos, C.A.C. Sequeira, B. Šljukić, Electrochim. Acta, 213 (2016) 298-305.

[2] C.G. Arges, V. Prabhakaran, L. Wang, V. Ramani, Int. J. Hydrogen Energy, 39 (2014) 14312-14321.

[3] Y. Ye, S. Sharick, E.M. Davis, K.I. Winey, Y.A. Elabd, ACS Macro Letters, 2 (2013) 575-580.

[4] L. Sun, J. Guo, J. Zhou, Q. Xu, D. Chu, R. Chen, J. Power Sources, 202 (2012) 70-77.
Nickel Nanoparticles Decorating Graphite Flake Surface Using Planetary Ball Milling: Physical Characterization and Methanol Electrooxidation Investigation
Authors: Garcia-Basabe Yunier , Rodrigues da Cunha Rafael Otoniel Ribeiro , Salgado Jose Ricardo Cezar , Larrude Dunieskys Gonzalez , Sossmeier Kelly Daiane
Published: February 2020

In recent years, several researches have been conducted in order to investigate the physical and chemical method for obtain the metallic nanoparticles, such as co-precipitation, hydrothermal, thermal decomposition of organometallic compounds, electrochemical, and ball milling method [1-4]. The particle size, shape and crystallinity depend on the selected synthesis method. In this sense the ball milling technique is one of the widely used to produce metallic nanoparticles, being the method feasible for large production [4].

A simple approach was proposed to obtain graphite surface decorated with nickel nanoparticles (Ni NPs) from dry ball milling process. Ni NPs were obtained after 40 h of high energy milling and 100, 200, 300 and 400 rpm ball rotation speeds. Both Ni NPs and graphite decorated samples were characterized by Scanning Transmission (STEM), Raman Spectroscopy, Scanning Electron Microscopy, X-ray diffraction pattern (XRD). The electrocatalytic activity of Ni/Graphite samples were evaluated from methanol oxidation in alkaline medium using electrochemical techniques.

Good agreement between STEM and XRD results can be found, reporting average diameter size of 4.9 nm and average crystallite size of 5.50 nm for Ni NPs. The methanol electrooxidation electrocatalytic activity was more efficient for Ni/Graphite with 100 rpm compared to Ni/Graphite others.

REFERENCES

M. Freire, T.S. Ribeiro, I.F. Vasconcelos, J.C. Denardin, E.B. Barros, M. Giuseppe, L. Carbone, S.E. Mazzetto, P.B.A. Fechine, MZnFe2O4 (M = Ni, Mn) cubic superparamagnetic nanoparticles obtained by hydrothermal synthesis, J. Nanopart. Res. 15 (2013) 1-12.

Alonso, P. Riente, J.A. Sirvent, M. Yus, Nickel nanoparticles in hydrogen-transfer reductions: Characterisation and nature of the catalyst, Appl. Catal. A 378 (2010) 42–51.

Aghazadeh, A.N. Golikand, M. Ghaemi, Synthesis, characterization, and electrochemical properties of ultrafine b-Ni(OH)2 nanoparticles, Int. J. Hydrogen Energy 36 (2011) 8674-8679.

F. de Carvalho, S.N. de Medeiros, M.A. Morales, A.L. Dantas, A.S. Carriço, Synthesis of magnetite nanoparticles by high energy ball milling Appl. Surf. Sci. 275 (2013) 84-87.
The Effect of Initial Chemical State of Copper Nanoparticles Towards C2 Products for Electrochemical CO2 Reduction
Authors: Jung Hyejin , Min Byoung Koun , Hwang Yun Jeong
Published: February 2020

The electrocatalytic reduction of CO2 to value-added products with utilizing the renewable electricity is a promising alternative for using fossil fuels and an attractive solution for mitigating the constant rise in atmospheric CO2 emissions.

Among all kinds of metal catalysts, copper is the only one that has capability to produce considerable amounts of hydrocarbons and alcohols at a moment. However, the selectivity control towards products is a main challenge for using a copper as a catalyst.

In recent studies, oxide-derived copper has emerged as an efficient electrocatalyst candidate for better C-C coupling ability and lower overpotentials. Although the reason for this enhanced ability is still under debate, the residual oxygen or Cu+ in nanostructured subsurface region has been proposed as a critical factor to improve selectivity towards C2 products and in-situ analyses examined this suggestion.

Here, we synthesized copper nanoparticles (NPs) directly grown on carbon support by wet-chemically facile one-pot method. We prepared two kinds of Cu NPs with different morphology and chemical state by controlling the synthesis temperature. The one is Cu2O with cube shape and the other is Cu/CuOx with sphere shape, which are confirmed by TEM, XPS and Cu K-edge XANES analysis. The electrocatalytic CO2 reduction reaction (CO2 RR) was conducted in 0.1 M KHCO3 aqueous solution and the effect of initial chemical state of copper on C2H4 selectivity was investigated. We observed that C2H4 selectivity is highly improved when the initial chemical state of copper nanoparticles is Cu2O compared to Cu/CuOx with the faradaic efficiency is 55 % and 20 %, respectively at -1.05 V (vs. RHE). For the verification of the reason for improved activity, we conducted XANES experiment and TEM analysis in the middle of CO2 RR. We conclude that the subsurface oxygen enhance catalytic activity and stability for ethylene production.

Figure 1. TEM images of (A) cubic Cu2O/C and (B) sphere Cu/CuOx/C

Figure 1
(Invited) Enhanced Photoelectrochemical and Photocatalytic Activities of CdS Nanowires By Surface Modification with Transition Metal Chalcogenides
Authors: Zhang Jin Z , Wang Hongmei , Li Chunhe , Bonabi Naghadeh Sara
Published: February 2020

Nanocomposites composed of one-dimensional (1D) CdS nanowires (NWs) and transition metal chalcogenide (such as NiS or MoS2) have been fabricated through a two-step solvothermal process. The as-prepared nanocomposites were characterized using a combination of techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) method, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), photoluminescence (PL) and photoelectrochemical (PEC) techniques. The properties of the nanocomposites strongly depend on the amount of transition metal chalcogenide. Compared with pristine CdS NWs, the optimal amount of transition metal chalcogenide results in enhanced photoelectrochemical (PEC) and photocatalytic activities for hydrogen evolution reaction (HER) in the presence of sacrificial agents. The enhanced PEC and HER activities are attributed to the intimate contact between CdS and transition metal chalcogenide that efficiently enhances charge carrier separation. To gain deeper insight into the mechanism behind the enhanced performance, ultrafast dynamics studies based on femtosecond transient absorption (TA) techniques have been applied to probe the charge carrier dynamics. The optimized nanocomposite showed higher average charge carrier lifetime than that of pure CdS NWs, potentially leading to more efficient charge separation and transfer. The dynamics results agree well with the photocatalytic results in that the longer charge carrier lifetime seems to correlate with improved performance in hydrogen evolution. This work demonstrates a facile approach to controlled synthesis of nanocomposites with well-defined structures for improved PEC and photocatalytic applications, particularly involving the use of biomass for HER from water splitting.
(Invited) Constructing Efficient Photocatalysts Based on the Bonding Difference
Authors: Liu Gang
Published: February 2020

Solar-driven photocatalysis represents a promising pathway of utilizing intermittent solar energy to produce storable chemical fuels from water splitting/CO2 reduction or to decompose pollutants in air/water environment. Photocatalysis can be divided into three basic steps, namely light absorption, charge separation and surface catalysis. Most stable photocatalysts suffer from the narrow visible light absorption range and/or high recombination probability of photogenerated charge carriers. Various strategies have been developed to address these challenges in the past decades. Controlling the compositions/defects of photocatalysts is an essential way of changing band structure of materials for a wide visible light absorption. Our ongoing studies on this topic demonstrate the substantial role of homogeneous distribution of electronic structure modifiers (dopants, defects, or disordering) in realizing band-to-band redshift of the absorption edge towards visible light region. Besides taking advantage of the natural diffusion pathways of some materials for electronic structure modifiers, another strategy we developed is weakening strong cation-anion bonds for an easy substitutional doping or introduction of anion vacancies. Some progress in producing a series of red anatase TiO2 and graphitic carbon nitride with strong visible light absorption has achieved. Constructing heterostructures of photocatalysts represents an important way of promoting the separation of photogenerated charge carriers. On the basis of the different bonding nature of different bonds in complex oxides, a series of complex oxide-binary oxide heterostructures were prepared by an in-situ process. As a consequence, the promoted charge separation is responsible for the enhanced photocatalytic activity.
Solar-to-Hydrogen Efficiency: Shining Light on Photoelectrochemical Device Performance
Authors: Young James L. , Döscher Henning , Geisz John F , Turner John A , Deutsch Todd G
Published: February 2020

Direct photoelectrochemical (PEC) hydrogen production aims to provide a clean and cost-effective solar fuel. Solar-to-hydrogen (STH) conversion efficiency is central to evaluating and comparing research results, and it largely establishes the prospect for successfully introducing commercial solar water-splitting systems. Present measurement practices do not follow well-defined standards, and common methods potentially impact research results and their implications. We demonstrate underestimated influence factors and experimental strategies for improved accuracy[1].

Our focus is tandem devices that have the prospect for greater STH efficiency[2], but increased complexity that requires more careful consideration of characterization practices. We perform measurements on an advanced version of the classical GaInP/GaAs design[3] while considering (i) calibration and adjustment of the illumination light-source; (ii) confirmation of the consistency of results by incident photon-to-current efficiency (IPCE), and (iii) definition and confinement of the active area of the device.

We propose applying the following standards for future PEC performance reporting: (i) traceable disclosure of the illumination-source configuration (lamp, filters, optics, PEC configuration) and/or its measured spectral distribution; (ii) thorough device-area definition including confinement of the illumination area and avoidance of indirect light paths; (iii) complementary IPCE confirmation of the solar-generation potential; (iv) proper consideration of faradaic efficiency. We will also give a brief overview of the PEC measurements and capabilities available at NREL to support academic and industry research.

[1] H. Döscher, J. L. Young, J. F. Geisz, J. A. Turner, and T. G. Deutsch, “Solar to hydrogen efficiency: Shining light on phoelectrochemical device performance,” Energy Environ. Sci. 2015.

[2] H. Döscher, J. F. Geisz, T. G. Deutsch, and J. A. Turner, “Sunlight absorption in water – efficiency and design implications for photoelectrochemical devices,” Energy Environ. Sci. 2014.

[3] O. Khaselev and J. A. Turner, “A Monolithic Photovoltaic-Photoelectrochemical Device for Hydrogen Production via Water Splitting,” Science. 1998.
Eradication of Candida Albicans Biofilm By Electrochemical Scaffold Producing Hypochlorous Acid
Authors: Zmuda Hannah M. , Kiamco Mia Mae , Mohamed Abdelrhman , Patel Robin , Beyenal Haluk
Published: February 2020

Biofilms are present in virtually all chronic wounds and contribute to the delay of wound healing. Biofilms are communities of bacterial and/or fungal cells embedded in an extracellular polymeric substance. Conventional treatment methods utilizing topical applications or systemic delivery of antibiotics are often inadequate because biofilms are inherently resistant to most of these approaches since the majority of antibiotics are active against metabolically-active, but not dormant, cells. The present study examines a new technology that can simultaneously eradicate biofilms on the wound surface and promote wound healing.

The electrochemical scaffold (e-scaffold) is a platform technology that allows controlled, continuous electrochemical production of low concentrations of biocides. The proposed novel e-scaffold consists of a three-electrode system, the working and counter electrodes are made of flexible carbon fabric, are accompanied by a Ag/AgCl reference electrode, controlled using a custom potentiostat. The e-scaffold works by electrochemically oxidizing chloride ions on the working electrode to chlorine gas when a constant potential of 1.5 VAg/AgCl is applied, and produces hypochlorous acid via chlorine dissolution. A phosphate buffer saline solution is added to the e-scaffold to provide chloride ions. While e-scaffold effectiveness in eradicating bacterial and antibiotic resistant bacterial biofilms was demonstrated in previous studies, its effectiveness against fungal biofilms has not been demonstrated. The goal of this work is to demonstrate the efficacy of the e-scaffold against in vitro
Candida albicans biofilm.

Fungal biofilms, such as C. albicans, differ from bacterial biofilms because fungal cells are eukaryotic cells and polymorphic, making fungal biofilms difficult to treat. After treating the C. albicans biofilm in an in vitro model with electrochemically produced hypochlorous acid using e-scaffold for 24 hours, the biofilm was completely eradicated. The results suggest that the electrochemical scaffold is a viable, new technology that can simultaneously eradicate antibiotic resistant fungal biofilms from the surfaces.
(Invited) Retrospective on Oxygen Reduction Electrocatalyst R&D Supported By the U.S. Department of Energy
Authors: Garland Nancy L.
Published: February 2020

Fuel cells are highly efficient energy conversion devices; they can operate on fuels such as natural gas, methane, and methanol as well as hydrogen generated using diverse domestic resources. Fuel cells are efficient, scalable, and can be used in a variety of applications - from the transportation sector to the generation of primary and secondary power. The U.S. Department of Energy’s (DOE's) Hydrogen and Fuel Cell Program supports early-stage research and development leading to energy security and resiliency, paving the way to a strong domestic economy. Because reducing cost and increasing durability remain as the major challenges in the advancement of fuel cell technology, early-stage R&D includes improvements in performance and durability and lower cost catalysts as well as membrane electrode assemblies for fuel cells and electrolyzers.

This presentation will describe the development of oxygen reduction catalysts for fuel cells focusing on the tremendous achievements from Dr. Adzic of Brookhaven National Laboratory. His association with DOE's Office of Energy Efficiency and Renewable Energy began in 2003 with the introduction of Platinum Monolayer Electrocatalysts and was extended to the broader concept of core-shell catalysts. As just a single recent example of the promise of the catalysts, Dr. Adzic and his team recently found that nitriding core components, such as NiPd alloy, in core-shell electrocatalysts resulted in a 50% reduction in Pd content compared to extant Pt/Pd/C catalysts and enhanced overall stability and activity. As a whole, the core shell catalysts have captured the attention of the industry and beyond resulting in U.S. patents, some of which have been licensed to catalyst producers. Other research groups have adopted BNL's concept of core-shell catalysts as well as the use of gold for increasing durability in catalysts. Not surprisingly, R&D 100 and many other awards have followed.
Field Testing of Floating Microbial Fuel Cells and Energy Harvesting Related Power Systems
Authors: Cristiani Pierangela , Bonelli Paolo , Liberale Alessandro , Tucci Matteo , Papacchini Maddalena , Trasatti Stefano P.
Published: February 2020

Microbial Fuel Cells (MFCs) are a promising technology to harvest energy from aquatic environments and act as sensing devices at the same time. Several prototypes of sediment MFCs have been tested in the past and more recently floating systems have been investigated as well, with encouraging results both in terms of energy harvesting and sensing. The challenge is now to scale up laboratory MFC designs for self-powering water quality sensors and implement these in real environments, where electricity sources may not be available. In this work, the performances of floating MFCs, suitably designed for aerobic and anaerobic water environments, were studied in long-term experiments. Several designs of flat and tubular cells were tested, using low-cost materials, such as plastic lunch boxes, and polystyrene or wood to keep the system afloat. Untreated carbon cloth, free of any chemical catalyst, was used for the electrodes. Flat MFCs were able to generate up to 15 mW/m2, depending on nutrient availability in the water. The electric performance of cathodes and anodes were differently correlated to chemical and physical water parameters (day/night cycle, chemical oxygen demand, total carbon content, nitrates and temperature among others). The Total Organic Carbon and Total Inorganic Carbon in the tank were continuously monitored with Sievers 820 Portable Total Organic Carbon Analyzer and compared to the current production of the cells.

Different types of power management systems had to be suitably designed, depending of the range of power produced by the MFC prototypes. A new generation of low-energy remote system (LORA) was integrated in an electronic circuit to harvest the power generated from MFCs and to transmit signals over long distance.

The experimentation was carried out in the wastewater plant site at Carimate (Figure 1), Como (Italy) and in the pool of the city garden “Orto Botanico Città Studi” at Milan (Italy).

Figure 1
Recell; A Closed-Loop Battery Recycling Model
Authors: Spangenberger Jeffrey , Gaines Linda , Dai Qiang
Published: February 2020

The number of plug-in electric vehicles sold in the U.S. has grown from 52,500 units in 2012 to over 160,000 vehicles sold in 2016; that is over a 300% increase in just four years. These vehicles’ batteries are going to reach auto dismantlers after approximately 10 years and require proper end-of-life processing, but the current solutions are not cost-effective. Argonne National Laboratory has developed a model that evaluates every stage of a battery’s life from material acquisition through recycling to provide a total cost and environmental impact. This allows for a direct comparison of virgin batteries to batteries with recycled content.