bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of Solar Fuels Photoanodes through Combinatorial Integration of Ni-La-Co-Ce Oxide and Ni-Fe-Co-Ce Oxide Catalysts on BiVO4
Authors: Haber Joel A. , Guevarra Dan , Shinde Aniketa , Zhou Lan , Sharp Ian D. , Toma Francesca M. , Gregoire John M.
Published: February 2020

The development of an efficient photoanode remains the primary materials challenge in the establishment of a scalable technology for solar water splitting. The typical photoanode architecture consists of a semiconductor light absorber coated with a metal oxide that serves a combination of functions, including corrosion protection, electrocatalysis, light trapping, hole transport, and elimination of deleterious recombination sites. To provide a more efficient exploration of metal oxide coatings for a given light absorber, we introduce a high throughput methodology wherein a uniform BiVO4 library is coated with 858 unique metal oxides covering a range of metal oxide loadings and the full Ni-La-Co-Ce oxide or Ni-Fe-Co-Ce oxide psuedo-quaternary composition spaces. Photoelectrochemical characterization of each photoanode reveals that approximately one third of the coatings lower the photoanode performance while select combinations of metal oxide composition and loading provide up to a 14-fold increase in the maximum photoelectrochemical power generation for oxygen evolution in pH 13 electrolyte. Particular Ce-rich coatings also exhibit an anti-reflection effect that further amplifies the performance, yielding a 20-fold enhancement in power conversion efficiency compared to bare BiVO4. By use of in situ optical spectroscopy and comparisons between the metal oxide coatings and their extrinsic optical and electrocatalytic properties, we present a suite of data-driven discoveries, including composition regions which form optimal interfaces with BiVO4 and photoanodes that are suitable for integration with a photocathode due to their excellent power conversion and solar transmission efficiencies. The initial high throughput discoveries were extended and validated through follow-up high throughput investigations and conventional photoelectrochemical measurements. The high throughput experimentation and informatics provides a powerful platform for both identifying the pertinent interfaces for further study and discovering high performance photoanodes for incorporation into efficient water splitting devices.
(Invited) In-Situ X-Ray Structural Characterization of Water-Splitting Catalysts in Artificial Photosynthesis
Authors: Tiede David M , Kwon Gihan , Kim In Soo , Emery Jonathan D , Martinson Alex B. F.
Published: February 2020

Resolution of structures and structural dynamics for catalysts at active electrode interfaces is necessary to resolve mechanisms for function and assembly in solar fuels applications. We have been developing porous, high-surface area, low X-ray background, 3-D electrodes for interfacial structural analysis of molecular and amorphous metal oxide water-splitting catalysts using X-ray scattering and atomic pair distribution function (PDF) analysis. We demonstrate the opportunity to use ALD-ITO coated microchannel plates and other micro- to nano-porous substrates for characterization of domain structures for amorphous metal oxides water-oxidation catalysts used in artificial leaf assemblies. This presentation will compare domain structures resolved for amorphous cobalt oxide films formed electrolytically as a function of ligand and electrolyte anion variation. For cobalt oxide catalysts, the results show that phosphate is unique in restricting domain size to small, single-layer domains where defects and edge distortions can be resolved. The results show that catalytic currents for do not scale with the domain edge content in the cobaltate films, which are the presumed sites for water oxidation catalysis, but instead track the extend of domain layering and conductivity properties of the films. These results support the view that overall catalytic activity in amorphous cobaltate thin films is determined by the charge accumulation and transport properties.  We have extended these techniques demonstrate the opportunity to measure PDF for homogeneous water oxidation catalysts. PDF measurements with 0.2 Å spatial resolution are found to be sufficient to resolve redox and catalytic state dependent changes in ligand structure.  This work establishes a foundation for extending the X-ray PDF method for the analysis of atomic structure changes in molecular catalysts driven by excited-state, sequential single electron photo-chemistry.
(Invited) On the Selectivity and Durability of Electrocatalysts for the Conversion of CO2 to Value Added Fuels
Authors: Zhou Xiao-Dong , Wu Jingjie
Published: February 2020

Rising emissions of CO2 in the atmosphere have become an increasing concern in recent years as growing evidence links greenhouse gasses to global warming, yet these emissions are the by-product of the majority of essential energy sources in place today (e.g. fossil fuels). In addition to efforts to capture and store CO2 in hopes of relieving the greenhouse effect, the conversion of CO2 to value added fuels and chemical feedstock is an attractive proposition that may provide an alternative solution to both the current energy crisis and climate issues. In this presentation, an overview will be provided on the utilization of a full electrochemical cell to study the selectivity of durability of metallic and nonmetallic electrocatalysts for the conversion of CO2 to gaseous or liquid fuels.  Special attention will be given to the chemical origin of selectivity and durability of this electrochemical process.
(Invited) 2D Nanosheet-Based Hybrid Photocatalysts for Solar Fuel Production
Authors: Hwang Seong-Ju
Published: February 2020

Solar energy is one of the promising renewable energy sources that can fulfill the rising global demand for sustainable energy.  One of the most effective approaches to harvest solar energy is the photoinduced production of solar fuel likes H2 and C1 compounds.  Despite a great deal of researches, most of inorganic photocatalysts ever-developed is not appropriate for the visible light-induced water splitting because of unsuitable band structure and poor stability.  To circumvent this problem, we have tried to synthesize hybrid-type visible light active photocatalysts via self-assembly between two kinds of nanostructured semiconductors including 2D nanosheets and 0D nanoclusters.  As building blocks, the 2D nanosheets of layered metal oxide, layered double hydroxide (LDH), and reduced graphene oxide (rG-O) are synthesized by the exfoliation process of the pristine layered materials.  The obtained 2D inorganic/rG-O nanosheets are reassembled with each other or hybridized with other 0D nanoparticles.  The band structure and surface area of wide bandgap layered metal oxide can be effectively tailored through the hybridization with LDH 2D nanosheets or transition metal oxide/metal chalcogenide 0D nanoparticles.  The obtained nanohybrids show promising photocatalytic activity to produce solar fuel under the irradiation of visible light.
Alternative Catalyst for CO2 Electrochemical Reduction
Authors: Varela Ana Sofia , Ju Wen , Roldan Beatriz , Strasser Peter , Mistry Hemma , Möller Timmey
Published: February 2020

Direct electrocatalytic conversion of CO2 to hydrocarbons is a promising alternative for the production of carbon based chemicals. Ideally, the driving force for this process would be electricity from renewable sources, making this process CO2 neutral.1 Copper is the most studied material as catalyst for CO2 reduction reaction (CO2RR) given its unique ability to produce hydrocarbons in considerable amounts. Nevertheless, the reaction’s poor energy efficiency and selectivity remain a major challenge.2 Therefore the technological viability of this process is contingent on the development of novel and efficient catalyst.

In recent years different groups have demonstrated that oxide derived copper foil catalysts exhibit lower onset potentials for CO2RR and high selectivities towards C2 products.3,4 Future applications, however, will require the use of supported nanoparticles. Herein we will present the use of Cu2O nanoparticles as catalyst for this process. We demonstrate that these nanoparticles have a lower onset potential for CO2RR in comparison with metallic Cu, which makes them a promising catalyst for this process.

Moreover we will discuss the use of alternative catalyst such as heteroatom-doped carbon.5 We show that these materials meet and exceed the activity and selectivity of traditional Au catalysts for the production of syngas, offering a cost-effective alternative. Furthermore, we provide evidence that sufficiently strong interaction between CO and the metal enables the protonation of CO to form hydrocarbons.  In order to get more insight into the role of  the metal atom, changes in the chemical stat under operando conditions observed via X-ray absorption fine-structure spectroscopy (XAFS) will be also discussed.

Figure 1: Scheme of the as heteroatom-doped carbon catalyst for CO2RR. b) Faradaic selectivities of CO and H2 after 10 min reaction at constant electrode potential in CO2 saturated 0.1M KHCO3 at 0.785 mg/cm2 catalyst loading. Lines to guide the eye.

References

(1) Gattrell, M.; Gupta, N.; Co, A. Ener. Convers. Manag.
007, 48, 1255.

(2) Kortlever, R.; Shen, J.; Schouten, K. J. P.; Calle-Vallejo, F.; Koper, M. T. M. J.Phys. Chem. Lett.
2015, 4073.

(3) Li, C. W.; Kanan, M. W. J. Am. Chem. Soc.
2012, 134, 7231.

(4) Kim, D.; Lee, S.; Ocon, J. D.; Jeong, B.; Lee, J. K.; Lee, J. Phys. Chem. Chem. Phys.
2015, 17, 824.

(5) Varela, A. S.; Ranjbar Sahraie, N.; Steinberg, J.; Ju, W.; Oh, H.-S.; Strasser, P. Angew. Chem. Int. Ed.
2015, 54, 10758.

Figure 1
(Invited) CO2 Photoreduction Under Visible Light By Oxygen-Deficient TiO2 with Co-Exposed {001} and {101} Facets
Authors: Li Ying , Liu Lianjun , Yang Kesong
Published: February 2020

This work for the first time reports engineered oxygen-deficient, blue TiO2 nanocrystals with co-exposed {101}-{001} facets (TiO2-x{001}-{101}) to enhance CO2 photoreduction under visible light. The TiO2-x{001}-{101} material demonstrated a relatively high quantum yield (0.31% under UV-vis and 0.134% under visible light) for CO2 reduction to CO by water vapor and more than four times higher visible light activity compared with TiO2 with a single {001} plane or {101} plane and TiO2(P25). Possible reasons are the exposure of more active sites (e.g., under-coordinated Ti atoms and oxygen vacancies), the facilitated electron transfer between {001} and {101} planes, and the formation of a new energy state (Ti3+) within TiO2 band gap to extend visible light response. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study was applied to understand the roles of co-exposed {001}-{101} facets and Ti3+ sites in activating surface intermediates. The in situ DRIFTS analysis suggested that the co-exposed {001}-{101} facets increased the capacity of reversible CO2 adsorption and that the combination of {001}-{101} and Ti3+ enhanced the activation and conversion kinetics of adsorbed species. The visible light responsive TiO2-x{001}-{101} material is not oxidized after long time exposure  to an air environment.
Carbon Negative CO2 Conversion with Atomically Precise Nanocatalysts
Authors: Kauffman Douglas R. , Matranga Christopher , Thakkar Jay , Siva Rajan , Jin Rongchao
Published: February 2020

Converting waste CO2 into fine chemicals and/or fuels is an exciting prospect for green-house gas mitigation. Electrocatalytic CO2 conversion is a leading candidate for this application because it operates at ambient conditions with extremely high reaction rates, product selectivity and faradaic efficiency. Carbon balance is a major consideration for any CO2 conversion technology because the majority of the United States' electricity is derived from burning fossil fuels. This necessarily shifts most CO2 conversion technologies into the carbon positive regime because CO2 emissions associated with fossil-fuel derived electricity will likely exceed that consumed by the conversion process. This limitation is an important challenge that must addressed before CO2 conversion technologies can be implemented on an industrial scale. Here, we describe a “carbon negative” (more CO2 consumed than produced) electrochemical CO2 conversion system based on atomically-precise Au25 nanocatalysts. The catalytic system operates on inexpensive (ca. $10-20 USD), consumer-grade photovoltaic cells and solar-rechargeable batteries. We show stable CO2 → CO conversion activity with turnover numbers (TON: mol CO2/mol catalyst) surpassing 5x106, rates exceeding 800 L CO2 /gram catalytic metal/hour, and faradaic efficiencies and product selectivities around 90%. These performance metrics correspond to 1-2 kg CO2 converted per gram of catalytic metal every hour. We can also tune product selectivity to favor CO or H2 production by varying the catalyst loading and/or operating voltage. We show stable operation for 12 hours with photovoltaic cells to represent daylight operation, and 24 hours with a solar-rechargeable battery to mimic low-light or night-time hours. This study provides proof-of-principle example that renewable-powered electrocatalysis is a viable strategy for CO2 conversion applications. The results were published in ACS Applied Materials and Interfaces
2015, 7, 15626.
(Invited) Chalcopyrites and III-V Semiconductors for Solar Water Splitting--a Detailed Look at the Electronic and Chemical Surface Structure
Authors: Heske Clemens , Blum Monika
Published: February 2020

This presentation will discuss the chemical and electronic surface properties of Cu(In,Ga)(S,Se)2- and GaInP2-based materials in view of their use in solar water-splitting devices. Many of the primary requirements for photoelectrochemistry (such as efficiency and stability) are directly related to such properties, but it is generally quite difficult to paint a comprehensive surface picture, in particular in operando environments.

The talk will focus on results obtained with a tool chest of soft x-ray and electron spectroscopies, with primary emphasis on high-brilliance synchrotron radiation experiments. It will be shown how photoelectron spectroscopy (PES), also under “ambient pressure” conditions, inverse photoemission (IPES), x-ray emission spectroscopy (XES), and x-ray absorption spectroscopy (XAS) can be suitably combined to derive surface electronic band gaps, study local chemical bonding and electronic level alignment, and gain insights into chemical stability.
Electrochemical Deposition of Cu2O Thin Film As Efficient Photocatalyst for Water Splitting Reaction
Authors: Hasan Maksudul , Mavrokefalos Christos K. , Compton Richard G , Rohan James F. , Foord John S.
Published: February 2020

Solar water splitting can form the basis of a sustainable hydrogen based energy economy, however the system requires optimisation in terms of cost and performance on a scale commensurate with the global energy demand. Photocatalysts consist of solar spectrum absorber semiconductor materials and co-catalysts as the redox mediator for hydrogen and oxygen evolution reactions. The key factors for efficient solar water splitting process to occur with such photocatalysts are a semiconductor with a sufficiently narrow band gap to absorb visible lights, a suitable thermodynamic potential for the redox reactions, and stability against photocorrosion. However, current photocatalysts also suffer from undesirable photoelectron-hole (charge carrier) recombination within the semiconductor due to their short diffusion path lengths and lifetimes, which results in fewer than 10% of the incident photons being used for water splitting.

Cuprous Oxide (Cu2O), one of the few naturally occurring p-type metal oxides, is the most promising candidate for an efficient photocathode because of its earth abundance, a band gap of 2.0 eV, which enables efficient visible light absorption, a scalable CMOS compatible deposition technique (e.g., electrodeposition), and favourable energy band position i.e. conduction band lies 0.7 eV negative of the hydrogen evolution potential that drives off half of the water reduction reaction without of any external bias. However, the application of Cu2O as photocathode is limited by two drawbacks; fast photoelectron–hole recombination owing to short carrier diffusion length and self-photo corrosion in aqueous solution under illumination since the potentials of Cu2O reduction and oxidation to metallic Cu and CuO, respectively, lie within the bandgap. Hence, the solar-to-fuel conversion efficiency on Cu2O depends on how fast the photoelectron can be extracted to the reduction reaction sites and inhibition of electrolyte access to Cu2O surface. A thin protective coating and a heterostructure in the seed layer of the electrochemically deposited Cu2O film enhance the overall photocatalytic performance versus the Cu2O film alone. The thickness of the Cu2O film was optimised to avoid the charge carrier recombination towards the efficient and stable photocatalytic performance. The photocatalytic performance of Cu2O thin film is shown in Fig 1, in which the film performance is unexpectedly high and only dropped to 22% after the first cycle at 0.0 VRHE, after which it stabilises. This presentation will discuss our current research to develop cheap and efficient photocatalysts and their enhancement mechanism towards photocatalytic water splitting reactions.

Figure 1
(Invited) Modeling and Its Use in Interpretation of Experimental Results for Electroactive Films at Electrodes
Authors: Sunde Svein , Tjelta Morten
Published: February 2020

Electrochemical characterization of electroactive films at electrodes requires models for interpretation of experimental results. Such films at electrodes may range in complexity from dense films for which uniform one-dimensional diffusion of intercalants provides an adequate description to porous systems with conductivity varying with state of charge and where more than one species may contribute to film conductivity. We describe here on-going attempts at extending models to these more complex situations within an analytical framework, and focus on interpretation of experimental results in view of the models. We thus review previous models suggested for describing the impedance of porous electroactive films of mixed conductivity, and extensions of the theory to include the effect of space charges within the porous matrix on the electrode capacitance. The Poisson-Boltzmann equation was thus solved for spherical geometry by use of Green’s functions, resulting in an analytical (closed form) integral expression that could be solved iteratively using a solution to the linearized Poisson-Boltzmann equation as the first order approximation for the potential. Practically identical results were produced when solving the governing equation by finite differences. Calculated concentration and potential profiles can be used to determine at which combination of carrier concentration and radius a particle is too small to sustain an extended space charge layer. Also, the surface capacitance-potential behavior has been obtained for extrinsically and intrinsically semiconducting particles. For the intrinsic case the behavior had a minimum value at the flatband potential. Extrinsic particles approached Mott-Schottky behavior at high dopant levels or large radii. These results will be discussed in the context of intercalation in porous electrodes, as well as extensions to other measurement methods than impedance.

References

[1] S. Sunde. I. A. Lervik, L.-E. Owe, and M. Tsypkin, “An impedance model for a Porous Intercalation Electrode with Mixed Conductivity”, J. Electrochem. Soc., 156 (2009) B927

[2] Sunde, S. , Lervik, I.A., Tsypkin, M., Owe, L.-E. , “Impedance analysis of nanostructured iridium oxide electrocatalysts”, Electrochimica Acta, 55 (2010) 7751 – 7760

[3] M. Tjelta and S. Sunde, “Current-distribution effects on the impedance of porous electrodes and electrodes covered with films”, J. Electroanal. Chem. 737 (2015) 65 -- 77
(Invited) Development of an Inductively Heated Ultramicroelectrode for SECM
Authors: Wipf David O , Dowell Timothy J
Published: February 2020

An underused parameter in electrochemistry is temperature. Controlling or altering the temperature at the electrode can provide several experimental benefits. Changes in kinetics and equilibrium constants are readily observed. Temperature dependent potential shifts and wave shapes can allow unique identification of chemical species. Thermal effects can also renew catalytic surfaces and improve mass transport by increasing diffusion coefficients or inducing convective currents.

Temperature control is readily achieved using thermostated electrochemical cells, but this produces several practical problems that may require addressing.  These include destruction of thermally unstable compounds, loss of volatile components, and reference electrode potential shifts.  In addition, the large thermal mass of an electrochemical cell does not favor rapid temperature changes.  These drawback can be minimized or eliminated by directly heating the electrode in a non-isothermal mode. (1)  For example, using high-voltage AC to heat cylindrical electrodes of mini to macroscopic dimension. These, and other types of electrode heating, produce a heated zone in the solution immediately adjacent to the electrode surface.  This then permits considering using temperature as a parameter in electrochemical imaging (cf. SECM) because of the potentially rapid temperature rise and fall at microscopic electrodes.  However, now several disadvantages are produced in the non-isothermal mode. These include reduced control over the temperature achieved, increased complexity of the experiment, and lower temperature precision.

Our goal is to develop heated-tip microelectrodes compatible with SECM and other SPM imaging.  We have developed a novel inductive heating procedure that can be used with electrodes of 1-20 μm. A small induction coil is placed entirely inside the electrode housing allowing the electrode shank to be heated by galvanically isolated induction. This electrode is physically small and is readily incorporated into the SECM instrument with no instrument modifications.

In this presentation, we demonstrate the rapid heating and cooling produced by the inductive method and show, using effects on kinetics and equilibrium potentials, that the temperature at the tip of the ultramicroelectrode may be altered up to the boiling point of the solvent. We also use finite element modelling to model the heating process and to estimate the temperature at the tip based on the geometry of the induction coil, the electrode material, the electrode body and any active cooling, and the solvent. In addition, we are modeling the rate of temperature rise and return to ambient relative to a heating pulse. Finally, we model the possibility of indirect, transient heating the imaged substrate by the heat flow from the closely-spaced heated tip.

 (1) Gründler, P.; Flechsig, G.-U. Microchim Acta 2006, 154 (3-4), 175–189.
Modeling Transport Phenomena in Ammonia Fuel Cells
Authors: Suh Dongmyung , Botte Gerardine G , Daramola Damilola A.
Published: February 2020

Introduction

Ammonia has been considered as a potential fuel for alkaline fuel cells. Ammonia can be produced at low cost, and inexpensive catalysts can be used in Ammonia Fuel Cells (AFC) [1, 2]. In AFC, ammonia is oxidized at the anode side and OH-, nitrogen and water are produced (1). OH- anion moves through membrane and reduced into water at the cathode side (2).

 1/3 NH3 + OH- ↔ 1/6 N2 + H2O + e-,  E0=0.40V   -----  Eqn. 1

1/4 O2 + 1/2 H2O + e- ↔ OH-,              E0=0.40V   -----  Eqn. 2

The theoretical open-circuit voltage (OCV) of the AFC is 1.17 V at standard conditions. The value is less than that of Hydrogen Fuel Cells (HFC), but AFC has a higher energy efficiency, 88.7%, than HFC of 83% [1].

Performance and durability of hydrogen PEM fuel cells has been improved over the last decade by extensive experiments and computations. In particular, continuum modeling has been an important tool for understanding and insight into processes and phenomena, which cannot be captured through experiments [3].

Recently, AFCs have attracted the attention of fuel cell researchers due to its high potential for a clean future energy device.  However, AFCs show some problems in related to mass transfer and fuel crossover in the membrane electrode assembly. In this study, transport phenomena in AFCs are analyzed using a computational model.

Objective

When the AFC is in operation, complex phenomena occur in the Membrane Electrode Assembly (MEA) including mass and heat transfer, electrochemical reactions, and charge (OH- and electron) transport (Fig.1). Therefore, a continuum model was developed to simulate the phenomena in MEA. 

Figure 1. Illustration of Mass Transport in Membrane Electrode Assembly depicting individual layers and chemical components. cCL and aCL depict the cathode and anode catalyst layers respectively, while cGDL and aGDL depict the cathode and anode gas diffusion layers respectively.

Results

Using the model, potential and species distribution in MEA, and the extent of electrochemical reaction in catalyst layer were calculated. In addition, the effect of different operating conditions on these phenomena were analyzed. These results, along with the effect of water transfer and ammonia crossover on cell performance will be discussed. Detailed accounts of the governing equations and their numerical solving procedure will also  be provided.

References

[1]           R. Lan and S. W. Tao, "Direct

Ammonia Alkaline Anion-Exchange Membrane Fuel Cells," Electrochemical and solid State Letters, vol. 13, pp. B83-B86, 2010.

[2]           M H. Assumpcao, S.G.Silva, and R. F. Souza, "Direct Ammonia Fuel Cell Performance using PTIR/C as anode electrocatalysts," Int. J. of Hydrogen Enrgy, vol. 39, pp.5148-5152, 2014.

 [3]          A. Z. Weber, R. L. Borup, "A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells," J. of The Electrochemical Society, Vol 161, ppF1254-F1299, 2014

Figure 1
Nitrogen-Doped Graphene/Sulfur Composite As Cathode Material for Room-Temperature Sodium-Sulfur Battery Application
Authors: Hao Yong , Li Xifei , Wang Chunlei
Published: February 2020

Sodium is a promising alternative anode material with advantages of high abundance, low cost, and suitable redox potential (~2.71 V). Sulfur, as one of the most abundant elements on earth, is considered as an attractive cathode material owing to its high theoretical capacity of 1675 mA h g-1 and high energy density of 2600 W h kg-1. It is well known that sodium-sulfur (Na-S) battery has been widely used for stationary energy storage, operating at a high temperature condition. In recent years, much effort has been devoted to develop Na-S batteries at ambient temperature to overcome the safety drawback [1-3]. However, more challenges exist in room temperature (RT) NaS batteries such as dissolution of intermediate polysulfides into the electrolyte, low utilization of active material, and poor cycle life. In this work, nitrogen-doped graphene nanosheets (NGNS) interlinked with sulfur has been used as an electrode material for RT Na-S batteries. This nanocomposite was synthesized via an chemical reaction-deposition and thermal treatment strategy. Two series samples with both high and low sulfur content levels in the nanocomposites have been developed. Characterizations testing such as SEM, XPS and XRD have been conducted and the results from electrochemical testing show that the first cycle discharge/charge capacities of the low loading sulfur-NGNS composite at 0.05C have been reached 212 mA h g-1 and 181 mA h g-1. The low loading sulfur-NGNS composite also presented notable cycling life with 300 cycles at 0.1C and the capacity remained at 55 mA h g-1, indicating good cyclic retention. Detailed discussion on the characterization and electrochemical performance of the synthesized NGNS/S nanocomposite will be presented in the meeting.

References

1.  T.H. Hwang, D.S. Jung, J.S. Kim, B.G. Kim, J.W. Choi, Nano Lett., 13, 4532 (2013).

2.  S. Xin, Y.X. Yin, Y.G. Guo, L.J. Wan, Adv. Mater., 26, 1261 (2014).

3.  S. Zheng, P. Han, Z. Han, P. Li, H. Zhang, J. Yang, Adv. Energy Mater., 4 (2014).
(Invited) Advantages of the Chloride-Containing All Vanadium Redox Flow Battery System
Authors: Li Liyu
Published: February 2020

In 2010, a novel all vanadium redox flow battery system was developed at the US Department of Energy’s (DOE) Pacific Northwest National Laboratory (PNNL), with the support of the US DOE Office of Electricity Delivery and Energy Reliability’s Grid Storage Program. This new system uses vanadium electrolyte with chloride-containing supporting solution, in which a stable complex between Cl- and V5+ forms. This new system was proved to have a much improved stability over the traditional sulfate based chemistry in small scales.

In the past three years, this advanced chloride-containin all vanadium redox flow battery system was extensively evaluated at UniEnergy Technologies, LLC (UET). The stability and cell performance of electrolyte solutions with different impurities were tested over a broad temperature window;  the performance of kW-scale and large-scale stacks was tested for thousands of cycles under various operation conditions; different testing and prototype systems, from 1 kW, 30 kW, to 100 kW, were developed and thoroughly tested for different applications; etc.

In 2014, the first commercial product of UET, Uni.System™, which delivers 600kW power and 2.2MWh energy in a compact footprint of only five 20’ containers, was successfully developed. This system integrates the abuse tolerant mixed acid vanadium electrolyte; a state-of-the-art containerized design derived from multiple decades of design experience among the UET team; optimized power electronics and controls at each system level (from cell to site); and mature large-scale stacks with more than 7 years of field deployment and over a dozen systems in the field.  In early 2015, a 1 MW-4 MWhr system, which consists of two Uni.SystemTM, was deployed in Pullman, WA by a utility company, Avista.

In this presentation, we will discuss what we’ve learned in the past three years about this advanced chloride-containing all vanadium redox flow battery system, especially the unique advantages of this system over the traditional sulfate system, and our understanding on the potential of this novel technology for various energy storage market applications.

Figure 1
Ionic Liquid Electrolytes for Rechargeable Aluminum Batteries
Authors: Wang Huali , Liu Gao , Bai Ying , Wu Chuan , Chen Shi , Wu Feng , Ling Min
Published: February 2020

Rechargeable aluminum battery is considered as a promising battery system used in energy storage devices, due to its abundant natural resources and high capacity. However, fabrication of this battery working at room temperature didn’t succeed until haloaluminate contained ionic liquids were used as electrolytes. Therefore, electrolytes are expected to have a great effect on performance of rechargeable aluminum battery. For ionic liquid electrolytes, anions play a major role in its electrochemical properties. Anion-effect of haloaluminate contained ionic liquids prepared with different halogenated imidazole salt and AlCl3/imidazolium chloride mole ratio are studied. Electrochemical window is found narrowing with reducibility of halide ion and AlCl3 mole fraction. When used as electrolyte in rechargeable aluminum battery with V2O5 nanowire cathode, AlCl3/[BMIM]Cl ionic liquid with the mole ration of  1.1:1 shows the best performance. The as-assembled cell exhibits a high discharge voltage platform (1 V) and capacity (288 mAh/g) at the first cycle. Concentration of Al2Cl7
- is considered as a key factor in chloroaluminate ionic liquids when used as electrolyte.

A slightly corrosion is found on the surface of Al metal foil immerged in acid AlCl3/[BMIM]Cl ionic liquids after 24 h. It means this kind of ionic liquids may help to remove the oxide film on Al metal foil. The oxide film is considered as a mainly hinder to performance of aluminum battery. Performance of battery using ionic liquid with other anions (such as BF4
-, PF6
- and CF3SO3
-) has not been reported, which is probably due to the dense Al2O3 film formed on surface of Al anode. It prevents the oxidation of Al in discharge process of battery and causes a failure.

Figure 1
Self-Sacrifice Template Formation of Hollow Hetero-Ni7S6/Co3S4 Nanoboxes with Intriguing Pseudo-Capacitance for High-Performance Supercapacitors
Authors: Hua Hui , Chen Qiuliu , Chen Zhiyi , Hou Linrui , Yuan Changzhou
Published: February 2020

Herein, we report a simple yet efficient self-sacrifice template protocol to smartly fabricate hollow hetero-Ni7S6/Co3S4 nanoboxes (Ni-Co-S NBs). Uniform nickel cobalt carbonate  nanocubes are first synthesized as the precursor via solvothermal strategy, and subsequently chemically sulfidized into hollow heter-Ni-Co-S NBs through anion-exchange process. When evaluated as electrodes for electrochemical capacitors (ECs), the resultant hetero-Ni-Co-S NBs visually exhibit attractive pesudo-capacitance in KOH just after contineously cyclic voltammetry (CV) scanning for 100 times. New insights into the underlying energy-storage mechanism of the hollow hetero-Ni-Co-S electrode, based on physicochemical characterizations and electrochemical evaluation, are first put forward that the electrochemically induced phase transformation gradually occurrs during CV sweep from the hetero-Ni-Co-S to bi-component-active NiOOH and CoOOH, which are the intrinsic charge-storage phases for the appealing Faradaic capacitance of hollow Ni-Co-S NBs at high rates (~677 F g-1 at 4 A g-1) after cycling. When further coupled with negative activated carbon (AC), the AC//hetero-Ni-Co-S asymmetric device with extended electrochemical window of 1.5 V demonstrates high specific energy density of ~31 Wh kg-1. Of significance, we strongly envision that hollow design concept and new findings here hold great promise for enriching synthetic chemistry and electrochemistry of complex metal sulfides for next-generation ECs.
Effect of Morphology on the Electrochemical Properties of Lithium Titanate Anode Materials
Authors: Li Jianling
Published: February 2020

Effect of morphology on the electrochemical properties of lithium titanate anode materials

Zhanyu Lia, Jianling Lia*, Yuguang Zhaoa, Kai Yangb, Fei Gaob

a State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, No. 30 College Road, Beijing 100083, China

b China electric power research institute, Beijing 100085, P. R. China)

* Corresponding author. Tel/ Fax: +86 10 6233 2651

Email Address: lijianling@ustb.edu.cn(J.Li)

    In recent years, Lithiumion batteries (LIBs) are popular electrochemical devices. In case of the anode, carbonaceous materials have been used as the most common commercial anode materials for LIBs. However, carbonaceous materials as anode material have a lot of problems in the safety and life. Therefore, there is an urgency to develop the LIBs with high power density, good cyclic stability and low cost. Recently, Li4Ti5O12 (LTO) has attracted much interest due to its potential application as an anode material for high-power LIBs.[1-3]

    In this work, two different morphologies of lithium titanate were synthesized by solid-state method and liquid phase method (as shown in Fig.1). It can be seen from Fig. 1 that the SEM image of LTO was synthesized liquid phase method (Fig.1b) shows uniform spheres morphology distributed, but LTO was synthesized solid-state method (Fig.1a) shows a little agglomeration. Fig.2 shows the rate capacity of LTO samples at different rates of 0.2 C, 0.5 C, 1 C, 2 C, 5 C and 10 C. It can be seen that the rate capacity of LTO obtained by liquid phase method is better than that of LTO synthesized by solid-state method. It may be attributed to the deagglomeration and uniform LTO crystallites that were generated by liquid phase method. Therefore, different morphologies have great influence on the electrochemical performance of LTO.

Fig.1. SEM image of Li4Ti5O12were synthesized by solid-state method (a) and liquid phase method (b)

Fig.2. Rate performances of LTO samples

Reference

 

Dunn B, Kamath H, Tarascon JM (2011) Electrical energy storage for the grid: a battery of choices. Science, 334: 928-935

Ying Y, Hao WY, Lai QY, Lu JZ, Chen YD, Ji XY (2008) A new composite material Li4Ti5O12-SnO2 for lithium-ion batteries. Ionics, 14:85-88

Zhou TP, Feng XY, Guo X, Wu WW, Cheng S, Xiang HF (2015) Solid-state synthesis and electrochemical performance of Ce-doped Li4Ti5O12 anode materials for lithium-ion batteries. Electrochim Acta, 174:369-374

Acknowledgments

The work was financially by the science and technology project of State Grid Corporation of china (DG71-15-042).

Figure 1
Flexible and Stretchable Lithium Ion Batteries Based on Solid Polymer Nanocomposite Electrolyte
Authors: Kammoun Mejdi
Published: February 2020

The strong demand for portable, ultra-thin, lightweight, flexible and stretchable devices, raises the need for new material and design concepts in battery technology that offer multi-functionality such as simultaneous electrochemical and mechanical functions. A key imperative in the development of the all-solid-state lithium ion batteries (LIBs) is the replacement of the traditional organic liquid electrolyte with high performance solid electrolyte. In this study, flexible and stretchable Li ion batteries are developed, based on solid nanocomposite polymer electrolyte (1% graphene oxide nanosheets in polyethylene oxide host), exhibiting capacities higher than 0.1 mAh cm-2 and excellent cycling stability over 100 charge/discharge cycles. Improvement in internal impedance of the battery is observed with the addition of 1% graphene oxide nanosheets to the polymer electrolyte. The energy density of the fabricated LIB is measured to be 4.8 mWh cm-3 at room temperature. The laminated LIB exhibits robust mechanical flexibility, good voltage retention over high bending and stretching cycles (i.e. over 6000 cycles) and good electrochemical performance in different configurations. Finite element analysis of the flexible and stretchable batteries provides critical insights into the evolution of mechanical stresses during lamination, bending and stretching.
Silver Modified MnO2 As an Electro-Catalyst for Oxygen Reduction Reaction in Alkaline Fuel-Cell and Battery Applications
Authors: Velraj Samgopiraj , Beverage Kevin , Wang Yuxuan , Li Zhe-Fei , Botte Gerardine G
Published: February 2020

The commercial viability of alkaline fuel cells and metal-air batteries as future energy applications hinges to a large extent on the development of highly efficient catalysts for the oxygen reduction reaction (ORR). Currently, platinum nanoparticles are the de facto cathode electrode materials to catalyze the sluggish ORR [1]. However, the scarcity of Pt metal coupled with their ever-growing demand are key obstacles for the broad deployment of this precious metal in all commercial technologies [2]. The logical solution to this persistent problem is an alternate catalyst with good ORR capabilities and durability at a reduced cost.

Several metals, metal-oxides, and non-metal based catalyst are being studied as alternate ORR catalysts with limited success [3]. Among metal-oxides, manganese oxide (MnO2) has gathered enormous interest due to their ability to catalyze the disproportionation reaction of HO2
- to H2O and catalyze 4-electron reduction of oxygen in combination with another material (usually carbon) active for 2-electron reduction of oxygen to peroxide [4]. Another method to improve ORR capabilities is to incorporate a small amount of noble metals in to the metal-oxide catalyst structure. It is expected that modifying catalysts with an inexpensive noble-metal such as silver would result in an improvement in the electrochemical performance of the cathode without significantly increasing catalyst cost. Additionally, the high activity of silver for oxygen reduction [5] and their superior electrical conductivity probably have additional synergy effect on the catalysts as shown for other bi-functional catalyst [6].

The objectives of this study are as follows: (i) synthesis and evaluation of MnO2 nanoparticles structure/morphology with and without silver, (ii) characterization of the synthesized catalyst materials using RDE to determine the effect of silver addition on the ORR kinetics, and, (iii) long-term durability testing of the cathodes prepared with different catalysts at higher current density to ensure their feasibility as ORR cathodes in alkaline media.

Fig. 1. shows the TEM and XRD of the MnO2 catalyst synthesized using the hydrothermal method. The XRD peaks of the catalyst powder as shown in Fig. 1a were identified as MnO2, while the TEM image shows a flake-like structure. Long-term durability testing of the MnO2-based cathode was performed using the three electrode cell design.

Fig. 2 shows the voltage measured at the cathode maintained at a constant current density of -150 mA.cm-2in 6 M KOH. Clearly, no noticeable drop in voltage was observed for 200 hr indicating good stability of the cathode for ORR over extended periods.

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Figure 1
A Versatile Measuring Setup for the Electrochemical Characterization of Materials Developed for Energy Storage Devices
Authors: Vyas Ritesh , Kubicsko Michael , Huber Benedikt , Drüschler Marcel
Published: February 2020

Recent development in the fields of energy storage and energy conversion has rapidly gained a fascinating momentum. A central aspect is the search for methods to enhance the safety, efficiency and durability of energy storage devices like lithium ion batteries. Particularly, the performance of the different components of such devices, like the electrodes, the electrolyte and the separator, as well as the interplay among them, has to be improved. Thus to characterize the properties of modified and novel materials, there is a need not only for measuring devices but also for measuring setups.

The Microcell HC setup offers different types of measuring cells which are suitable for the electrochemical characterization of liquids, gels, and polymers with a low to high viscosity as well as the characterization of solid samples [1]. Depending on the measuring cell, the measurements can be performed in both a two- and three-electrode setup. During measurements the temperature of the sample can be controlled quickly and precisely. Only a small sample volume (milligram range) is required, which allows for electrochemical analyses of substances that are only available in small amounts and/or extremely expensive.

Already established applications of the setup are the measurement of the conductivity of ionic liquids, polyelectrolytes [2], and polymer electrolytes, electrochemical impedance spectroscopy for the characterization of the interface ionic liquid/electrode [3], and cyclic voltammetry for a large variety of electrochemical systems [4]. Especially cyclic voltammetry experiments, but also measurements utilizing a three-electrode setup, require a reference electrode. For electrochemical measurements on ionic liquids or carbonate based electrolytes, a microreference electrode can be used [5].

Literature:

[1] B. Huber, M. Drüschler, B. Roling, Nachrichten aus der Chemie
2012, 60, 1213- 1214. [2] B. Huber, L. Rossrucker, J. Sundermeyer, B. Roling, Solid State Ionics
2013, 247-248, 15-21. [3] J. Wallauer, M. Drüschler, B. Huber, B. Roling, Z. Naturforsch.
2013, 68b, 1143-1153. [4] J. Schwaben, N. Münster, T. Breuer, M. Klues, K. Harms, G. Witte, U. Koert, Eur. J. Org. Chem.
2013, 2013, 1639-1643. [5] B. Huber, B. Roling, Electrochim. Acta
2011, 56, 6569-6572.
Aqueous Ion Intercalation in Hydrous Oxides
Authors: Lo William , Wang Ruocun , Augustyn Veronica
Published: February 2020

Transition metal oxides are often the materials of choice for energy storage and conversion applications due to their numerous oxidation states, mixed electronic/ionic conductivity, and structural variability. Here, we describe the electrochemical behavior of hydrous hexavalent tungsten and molybdenum oxides (WO3 and MoO3, respectively) as model material systems for investigating aqueous intercalation mechanisms.  These oxides offer the benefits of multi-valent transition metal redox, diversity of crystal structure, hydrated polymorphs, and a variety of synthesis techniques that yield bulk powders, nanomaterials, and nanosheets.  The mechanism of ion intercalation is dependent upon two different regions of the material:  the internal structure, or the solid-state environment that controls the ion diffusion and favorable storage sites, and the external surface, or the nature of the electrochemical interface which controls the charge-transfer step of the intercalation reaction as well as stability.  We characterize the behavior of these oxides in a variety of aqueous electrolytes in order to understand the effect of electrolyte ion size, charge, and hydration on the intercalation mechanism. We find that the presence of structural water and the nature of the intercalating ion both result in significant effects on the aqueous intercalation mechanism in tungsten and molybdenum oxides.
Transparent and Flexible Energy Storage Using Pseudocapacitive Ni(OH)2 coated Cu Nanowires By Solution-Processes
Authors: Thostenson James O. , Cordova Isvar A. , Stewart Ian E. , Amsden Jason J. , Parker Charles B. , Liu Jie , Wiley Benjamin J. , Glass Jeffrey T.
Published: February 2020

Realization of cost-effective energy storage that is both safe and scalable relies on the ease with which it can be integrated into existing manufacturing technology. Roll-to-roll and solution-based processes are two such technologies that offer the ability to deposit flexible films of controlled thickness for a low cost device. Our work uses one such approach to build a transparent and flexible pseudocapacitive electrode using earth-abundant and low cost materials. The electrode is comprised of a core/shell Cu/Ni(OH)2 structure of nanowires (NWs) on a glass slide. In order to understand the effects of both NW network density and the thickness of the Ni(OH)2 shell, we utilize Meyer rod and electroless plating techniques to control the network density and shell thickness, respectively. Our study uses NW networks with resistance of <50 Ω/sq. and >60% transmittance to investigate the performance of Ni(OH)2shells with 20, 30, and 40 mol% Ni, with respect to the conductive Cu core.

Controlling the Cu NW density and Ni(OH)2 shell thickness yields capacitances of 800 F/g and 2550 μF/cm2 at 0.02 mA/cm2 charge-discharge current density with >70% transmittance. The 30 mol% Ni on Cu NW structure exhibits higher gravimetric capacitances than the 20 and 40 mol% Ni structures. We propose that these differences are due to diffusion limitations limiting the amount of electrochemically active material and to the density of active NWs, which impacts the sheet resistance of the underlying conductive NW network. In addition, the quasi-1D Ni(OH)2 structure of our NW devices enabled highly reversible pseudocapacitive intercalation and remarkably stable performance under fast charge-discharge rates, exhibiting coulombic efficiencies of >90% with only a 13% decrease in capacitance after 10,000 cycles for the thicker 40 mol% Ni(OH)2 shell.

Our continuing and future work in exploring the Cu/Ni(OH)2 NW material is to further stabilize and improve both areal and gravimetric capacitance while we investigate the use of a flexible polypropylene (PPE) substrate. Preliminary results show that the electrode can be bent at a 90° angle and retain capacitive behavior beyond 12 hrs in solution. Additionally, we seek to match our electrode’s characteristics with a suitable counter electrode and solid-state electrolyte to construct a fully flexible, hybrid supercapacitor device.

Figure 1