bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Sodium Fluoride and Sodium Lignosulphonate Additives on Performance of the Soluble Lead Redox Flow Battery
Authors: Suman Rathod , Ravikumar Musuwathi Krishnamoorthy , Jaiswal Nandini , Patil Satish , Shukla Ashok Kumar
Published: February 2020

Soluble lead redox flow battery (SLRFB) is a flow battery with a common electrolyte and can be developed in undivided, divided and semi-divided configurations [1]. At present, the development of SLRFB is hindered mainly due to (i) the formation of lead dendrites at anode, (ii) oxygen evolution reaction (OER) at cathode and (iii) accumulation of PbO2 due to poor electrode kinetics [2]. In an earlier study, we have reported a study on extending the cycle-life of SLRFB using an auxiliary electrode concept [3]. In the present study, we report the independent and combined effects of adding sodium lignosulfonate (SLS) and sodium fluoride (NaF) to the electrolyte as anode and cathode benefitting additives, respectively. The study reveals that adding 4.2 gm/L NaF alone improves the kinetics of both electrode reactions as compared to that with no additive but fails to prevent dendrite formation. Adding 1 gm/L SLS alone has beneficial effect on anode by preventing dendrite formation but the concentration of SLS gradually decreases with the cycling of the battery. The combined effect of adding SLS and NaF depends on the concentration of SLS. It is observed that adding low concentration of SLS 0.2 gm/L along with 4.2 gm/L NaF has beneficial effect on both the anode and cathode reactions and hence maintaining this concentration would help extending the cycle-life of SLRFB. The individual as well as combined effects of these additives on the reaction products is studied by quasi in situ XRD and FESEM techniques. The effect on electrode kinetics and cycle life are also reported.

References

1. M. Krishna, R.G.A. Wills, A.A. Sha, D. Hall and J. Collins, J. Appl. Electrochem.,
48(9) 1031 (2018)

2. D. Pletcher, ECS Transactions,
28(16) 1 (2010)

3. R. Suman, M.K. Ravikumar, N. Jaiswal, S. Patil and A.K. Shukla, ECS Meeting 233, Abstract no. MA2018-01, 221 (2018)

Acknowledgements

Financial support from UKRI Global Challenge Research Fund project, SUNRISE (EP/P032591/1) and DST, New Delhi is gratefully acknowledged.

Figure 1
Nature-Derived Organic Mesomeric Electrolyte for Low Cost and High Capacity Aqueous Flow Battery
Authors: Zhu Hongli
Published: February 2020

Organic redox flow batteries have the potential to surpass the challenges posed by inorganic electrolytes commonly used in flow batteries, thus achieving high performance and a sophisticated storage solution for the grid. Herein, we demonstrated a high performance aqueous organic redox flow battery (AORFB) utilizing a redox active resource from nature, IC, as the anolyte. The IC-H is obtained through substitution of sodium ions with protons (H+). The aqueous solubility was increased dramatically from 0.035 M to 0.760 M (theoretical capacity ~37.0 Ah L-1 and theoretical energy density ~28.2 Wh L-1) in protic solvents by enhancing hydrogen bonding. The revealed diffusion coefficients (IC-Na: 3.38 ×10-5 and IC-H: 2.23 ×10-5 cm 2 s −1) and reaction rate constants (IC-Na: 2.32 × 10-4 and IC-H: 2.82 ×10-4 cm s-1) indicate rapid reaction kinetics. The highly soluble constructs high-performance AORFB, when paired with bromine/hydrobromic acid catholyte, exhibiting high capacity of 24.2 Ah L-1 at 40 mA cm-2 with round-trip energy efficiency and capacity retention exceeding 77 % and 99.96 % per cycle. Moreover, computational study signifies the prospect of further improvements in solubility and voltage window by tuning the structure. Therefore, the environmentally benign and earth-abundant natural dye represents a promising choice for green and sustainable redox active anolyte of AORFB.
(Invited) High-Energy-Density Redox-Flow Batteries: Fundamental Redox Processes and Materials Design Strategies
Authors: Lu Yi-Chun
Published: February 2020

Energy storage system is a critical enabling factor for deploying unstable and intermittent renewable power sources such as solar and wind power sources. Redox flow batteries (RFBs) offer unique advantages of high efficiency, low cost, scalability and rapid response for grid energy storage. One of the most critical bottlenecks of RFBs is their low energy density, which is strongly related to the cell voltage and the solubility of the active materials. In this presentation, we will discuss strategies to improve the energy density of aqueous and nonaqueous RFBs and spectroscopic investigation on the redox processes involved in these RFB systems. Design strategies including redox complexing agent (e.g. lithium iodide, lithium bromide), semi-solid approach (e.g. sulfur/C and organic molecules), self-mediation approach, and highly-concentrated organic molecules (e.g. ferrocene-based) will be discussed. The influence of flow rate and current density on the electrochemical performance under continuous/intermittent flow modes as well as the synergistic interplay between solvent and redox-active materials in solid and liquid phases will be discussed.

Acknowledgement:

This work was fully supported by a grant from the Research Grant Council of the Hong Kong Special Administrative Region, China (Project No. T23-601/17-R).
Optimally Engineered Flow-through Electrodes Using Automatic Design Algorithms and Additive Manufacturing
Authors: Beck Victor A , Weisgraber Todd H , Ivanovskaya Anna N , Chandrasekaran Swetha , Moran Bryan D , Watts Seth E , Tortorelli Dan A , Duoss Eric B , Biener Juergen , Stadermann Michael , Worsley Marcus A.
Published: February 2020

Flow batteries are a promising technology for large scale energy storage and load balancing from intermittent power sources, but their viability hinges on our ability to attain high-power outputs while minimizing costs and meeting performance constraints. Controlling fluid flow, active species distribution, and mass transport in the electrode has a dramatic impact on cell power and efficiency. However, this control is often limited to changing a quasi-two-dimensional flow field and selecting bulk properties of a monolithic electrode. This can lead to non-uniform reaction rates, underutilized regions of the flow cell, and can limit the ultimate performance of the devices. We propose an alternative approach which seeks to control the fluid distribution in the cell by controlling the electrode geometry. Our approach is enabled by additive manufacturing techniques which allow us to directly build three-dimensional morphologies. Further, to determine effective electrode geometries, we employ topology optimization techniques that couple solution of the forward electrochemical problem over the full electrode domain with gradient-based optimization. The output of our code is a three-dimensional CAD representation which optimizes over specific performance metrics and which can be used to print functional electrodes. We will demonstrate the process for generating the electrodes using our optimization framework and present experiments comparing the performance of the optimized geometries across designs and against conventional electrodes. This work provides a systematic path toward automatic design of engineered electrodes with precise control over the fluid and species distribution.

LLNL-ABS-764035

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
A No-Mixing Design of Vanadium Redox Flow Batteries
Authors: Liu Baichen , Zhu Runfan , Sun Jie , Zheng Menglian
Published: February 2020

Vanadium redox flow batteries are expected to play an important role in the future energy systems with increasing intermittent renewables. Over the past few decades, the performance of vanadium redox flow batteries has improved significantly in terms of such as power density, voltage and columbic efficiencies. However, the effective energy capacity has not yet reached the theoretical value, partly because of the large concentration discrepancies of the active species in the tank and stack during the (dis-)charging processes. In order to alleviate this concentration discrepancy and thus enhance the effective energy capacity and economics of the vanadium redox flow battery, the authors develop a no-mixing design with two additional tanks and two extra pumps being added to the battery system. As such, the mixing of the (dis-)charged and un(dis-)charged electrolytes in tanks during (dis-)charge processes can be alleviated to certain extent. Some main findings include: First, both experimental and simulative results show that the no-mixing design can effectively improve the effective capacity and voltage efficiency by more than 10% and 2%, respectively, compared to the conventional two-tank system. In addition, the efficiency increment in the effective capacity rises with increasing electrolyte volumes and decreasing flow rates. Moreover, an analytical approach for estimating the benchmarked enhancement of the effective energy capacity in the no-mixing design is also provided in the present study. With the alleviated concentration discrepancy and increased benchmarked enhancement of the effective energy capacity, the no-mixing design is recommended to be adopted in the applications that require a large amount of electrolytes, i.e., relatively large electrolyte volume. And last, some new industrial setups based on the no-mixing design are proposed, such as gravity-driven or pressure-driven setups, to enhance the industrial practicability of the no-mixing design. The no-mixing design is also shown to be one of the possibilities to achieve pumpless system for reduced pump consumption in the future, especially for non-aqueous redox flow batteries with high viscosity electrolytes.
(Invited) RKP Vanadium Flow Battery and its Application
Authors: Ma Xiangkun , Zhang Huamin , Xu Xiaobo , Jiang Shan , Wu Jingbo , Chigan Ting , Wang Hongbo , Zhao Haijun , Chen Ning
Published: February 2020

Vanadium flow battery(VFB) is deemed to be one of the most promising technologies for large-scale industrial energy storage, due to its attractive features like flexible capacity, active thermal management, long cycle life and high safety. Dalian Rongke Power Co., Ltd. (RKP) has been devoted to the fundmental study and advanced research of Vanadium flow battery applications. It has become one of the world-leading enterprises in VFB development, manufacturing and delivery industry. The products have evolved from earlier indoor structure to the latest containerized system designs. More than a dozen VRFB systems have been deployed and end products have been launched into operations across the world over the past decades.

The 500kW/2MWh VFB product was developed for the large scale energy application, which is consisted of 16 cell stacks. The high integration level, low shunt current loss, low auxiliary power supply consumption and high reliability were achieved. The novel cell stack is designed by optimizing the key materials and cell stack structure, which can achieve a better performance and higher reliability at a relatively low cost. The energy efficiency(EE) could reach 80% at the rated power of 33kW, and the current density could be improved to 140~150 mA/cm2.The cycle life test indicated that no obvious performance decay was found even after 10000 cycles. The advanced two-stage power conversion system (PCS) was selected in order to realiaze the independent control of each sub-systems, which would improve the overall reliability ultimately. The AC/AC energy efficiency could reach 70% at the rated power of 500kW. The 500kW/2MWh VFB product has been installed in power plants for wind and solar energy storage and has obtained better application effect.

The world largest battery system, a 200MW/800MWh VFB peaking power plant conducted by RKP, is currently in progress in Dalian, China. The purpose is to improve the Northeast grid resiliency and facilitate smooth integration of renewables. A 500kW/2MWh VFB product is the minimum storage unit of the project. Each unit product could be controled independently. The foreseeable success of the project would exert great influence on the development of the flow battery in the future.

In this presentation, new technolgy and product developments of vanadium flow battery at RKP will be introduced and further challenges will be addressed as well.
Iron(tris pyridyl-imine) Complexes As Redox Couples for Non-Aqueous Redox Flow Battery Applications
Authors: Maurya Sandip , Smythe Nathan , Davis Benjamin L , Andrade Gabriel , Sharma Shikha , Park Eun Joo , Gordon John , Kim Yu Seung , Mukundan Rangachary
Published: February 2020

Grid-scale energy storage technologies are much needed for efficient integration of intermittent energy sources, such as wind and solar, into the electrical grid. Redox flow batteries (RFBs) have decoupled power and stored energy qualities, in contrast to traditional batteries, storing energy chemically in scalable solutions, and thus have the potential to solve the large-scale energy storage issue. Conventional redox flow chemistries are aqueous-based, such as Iron-chrome and all vanadium, where operating cell voltages are limited by water splitting reactions. Therefore, non-aqueous RFBs, which can operate at much higher voltages, are gaining attention and are typically only limited by the potential window of the non-aqueous solvent. Despite having enlarged potential windows that could provide higher energy density, most of the non-aqueous RFBs still operate at very low concentration, current densities and suffer from poor cycle life. In addition, the high cost of metals, such as vanadium, ruthenium, cobalt, etc., are an obstacle to achieving the DOE’s long term target of 150 USD per kWh for RFBs.

In this presentation, therefore, we will discuss the synthesis and characterization of iron pyridine-imine complexes for redox couples. The performance of these redox couples in a bulk electrolysis cell and flow battery set-up will also be discussed. A mechanistic study to understand the fundamental degradation mechanisms of the redox couples under continuous charge/discharge operations will also be discussed. Our results indicate that iron complexes possess good reversibility and have the potential to compete, and potentially replace, other redox systems used in non-aqueous RFBs.

Acknowledgement

This work is supported by the Laboratory Directed Research & Development Program at Los Alamos National Laboratory.
Diketopyrrolopyrrole Based Derivative for Non-Aqueous Redox Flow Battery
Authors: Sharma Shikha , Suman Rathod , Ray Suman , Aetukuri Nagaphani , Shukla Ashok Kumar , Patil Satish
Published: February 2020

Non-aqueous Redox Flow Batteries (RFBs) exploiting the wider electrochemical potential gap between catholyte and anolyte operate at higher cell voltages and lead to high energy and power densities with compelling energy efficiencies. However, stable anolytes are rare, primarily due to their low stability in presence of oxygen and moisture. The inherent atmospheric reactivity of anolyte puts a formidable demand to judiciously design molecules with high electron affinity and electrochemical stability. In this study, a non-aqueous organic RFB utilizing the redox pair is demonstrated employing commercially available Unisol blue (UB) dye (1,4-bis(isopropylamino) anthraquinone) as catholyte and air stable diketopyrrolopyrrole (DPP)-based derivative as anolyte. Cyclic voltammetry measurements with repeated sweep scans over 200 cycles are performed to find the redox potentials for both materials and electrochemical stability of the redox couple. The electrochemical performance of the RFB is studied by assembling cell with UB and DPP as redox pair. The study opens up a route to design/select molecules for non-aqueous RFBs.
Mechanically Robust Crosslinked Membranes for Non-Aqueous Redox Flow Batteries
Authors: Lehmann Michelle , Yang Guang , Self Ethan Craig , Li Bingrui , Delnick Frank M. , Nanda Jagjit , Saito Tomonori
Published: February 2020

Non-aqueous redox flow batteries (RFBs) are potential alternatives to aqueous redox flow systems for large scale energy storage. The advantages of non-aqueous RFB’s over aqueous systems are a larger voltage operating window, wider temperature range and the potential for increased energy density. A sodium-based system is of interest due to sodium’s low cost and natural abundance. One major challenge for non-aqueous RFB’s is the lack of high performance membranes that can withstand their operation conditions. A membrane for an RFB needs to possess sufficient mechanical strength, high conductivity, ion selectivity and excellent chemical resistance. In this project, mechanically robust, chemically resistant, crosslinked membranes have been fabricated via thermal or UV curing. In one system, crosslinked poly(ethylene oxide)-based membranes containing 10 wt% to 40 wt% sodium triflate have been studied as dry and plasticized samples. Careful tailoring of the crosslinking chemistry allows the membranes to be free standing, flexible and robust with and without plasticizer. The membranes are stable over a wide temperature range, with a constant storage modulus of ~1 MPa from -20 °C to 180 °C even with the addition of plasticizer. The mechanical strength of the membranes is enhanced by 3 orders of magnitude to above 1 GPa with the addition of an inorganic filler, without any significant adverse effect on ionic conductivity. Specific ionic conductivities up to 2.0 x 10-4 S/cm at 20 °C and 7.1 x 10-4 S/cm at 70 °C are achieved for the plasticized membrane, while ionic conductivities for the dry membrane are 3.0 x 10 -6 S/cm at 20°C and 6.4 x 10-5 S/cm at 70 °C. Furthermore, our efforts on the synthesis and characterization of sodium sulfonate functionalized cation exchange membranes will be discussed.

This work is funded by Dr. Imre Gyuk, Office of Electricity Delivery and Reliability, Department of Energy and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC.”
Effect of Surfactant for PTFE Binder Dispersion of Electrodes Prepared By Bar Coating Method in High Temperature Polymer Electrolyte Membrane Fuel Cell
Authors: Lee Min Jae , Lee Ju Sung , Lee So Young , Kim Hyoung-Juhn , Song Kwang Ho
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFCs) are one of the most promising energy devices for both mobile and stationary applications due to their high energy conversion efficiency and low environment pollution. However, there are some problems to be solved. PEMFCs operating at low temperatures (below 80℃) based on Nafion require humidification and have low CO tolerance. To overcome this problem, high-temperature PEMFCs that operate up to 180℃ are being studied. High temperature PEMFCs does not require humidification, which simplifies the system and is highly resistant to CO. It also has the advantage of using waste heat. However, the cell performance of high-temperature PEMFCs is still much lower than that of low-temperature PEMFCs and needs to be increased for practical applications

The reason for this is slow Oxygen Reduction Reaction (ORR) and limited transport of protons and reactants, especially in the presence of phosphoric acid in the catalyst layer. In the high-temperature PEMFCs, phosphoric acid acts as a proton conduction as an electrolyte and is a necessary element for electrochemical reactions at the triple phase boundaries. Therefore, if the amount of phosphoric acid in the catalyst layer is too small, it exhibits low electrochemical activity. If it is too much, the pore inside the catalyst layer is blocked to restrict the movement of the fuel, thereby reducing the number of triple phase boundaries and reducing the performance. Therefore, the amount and distribution of phosphoric acid and the formation of structural network pores in the catalyst layer are important. Thus, several polymeric binders have been introduced to perform this role. Among them, PTFE is known as the most promising binder. PTFE has hydrophobicity and high chemical stability. However, PTFE easily agglomerates and sinks immediately in the solvent due to its high hydrophobicity. Therefore, if an electrode is made of a catalyst slurry that does not properly disperse PTFE, uniform PTFE distribution in the catalyst layer cannot be expected. So, in the catalyst layer, there may be more or less parts of the specific part than the desired PTFE content. Therefore, it is not only difficult to form a proper phosphoric acid distribution and structural network of the catalyst layer, but also may affect the reproducibility of electrode manufacturing.

In this study, the catalytic electrode was prepared by introducing a surfactant to disperse PTFE in the preparation of catalyst slurry. Single cell test was carried out using membrane electrode assembly made from this electrode. And the electrochemical and structural characterizations were compared. The details will be discussed in presentation.
(Invited) Enabling Conversion-Based Metal Oxide Anodes for Li Ion Batteries through Material Confinement
Authors: Ng Benjamin , Mustain William E.
Published: February 2020

The market demand for electric vehicles (EVs) and hybrid electric vehicles (HEVs) have pushed Li-based technologies towards new higher capacity materials. The end goal is to enable full EVs that recharge very quickly (5-10 min) and achieve similar driving range to fossil-fuel cars (400-500 miles). State of the art Li ion batteries can deliver a gravimetric energy density of approximately 250 Wh kg-1, which is equivalent to ~250 miles for an EV. For EVs to truly compete in the market, batteries with an energy density greater than 500 Wh kg-1 must be realized. One family of materials that has been proposed to replace graphite at the anode is conversion metal oxides, which have both higher capacity (700-1200 mAh/g vs. 372 mAh/g) and slightly higher operating potential. This means that metal oxides have the potential to concomitantly increase energy density and improve safety (by avoiding Li plating during fast charge). Unfortunately, many of the metal oxide anodes that have been reported in the literature have shown poor cycle life and low coulombic efficiency.

In this presentation, we will discuss each of the degradation mechanisms that act to reduce capacity, capacity retention and coulombic efficiency of conversion metal oxides in Li-ion batteries. We will present new data on the influence of the electronic conductivity of these materials as well as the growth dynamics of the solid electrolyte interphase (SEI). It will be shown that there are two primary degradation pathways for metal oxide anodes in lithiuim ion batteries and a new strategy based on material confinement will be presented to simultaneously mitigate both. A combination of physical (TEM, S/TEM, XPS) and electrochemical (charge/discharge, EIS) characterization will be used to explain the behavior of these materials, and materials combinations that allow for achieved capacity of 800 mAh/g, capacity retention over 1000’s of cycles and coulombic efficiency > 99.5% will be presented.
Oxygen Transport Resistance in PEMFC Catalyst Layer Based on Ultra-Micro Electrode (UME) Theory
Authors: Lu Zijie , Yang Jun , Xu Chunchuan , Wang Chunmei , Waldecker James
Published: February 2020

Hydrogen fuel cell is a promising zero-emission automotive powertrain for larger vehicles with long-distance requirements. However, its cost must be reduced to achieve real commercial use. Minimizing use of precious metal catalysts and increasing the fuel cell power density have been the most viable means to reduce the stack cost. Focus of advanced research is shifting to improve the fuel cell power density (> 1 W/cm2) with low Pt-loaded catalyst layers (≤ 0.125 mgPt/cm2 total).

One of the emerging issues with the low loaded fuel cell electrode is the dramatic increase of oxygen transport resistance with Pt loading reduction. This has been observed for both diluted (with addition of carbon particles to maintain the layer thickness) and undiluted (thinner) electrodes. The mechanism for the transport resistance increase in low Pt loaded electrode is not well understood and the quantitative modeling of the resistance is scarce. In this work, we propose a simple explanation to the oxygen transport in the catalyst layer based on the assumption that each active Pt particle functions as a semi-spherical nano-electrode, which is covered by a layer of proton conducting matter (ionomer, water film, or a combination of two). Without any other assumption, the oxygen transport resistance in the catalyst layer can be analytically determined, for the case of limiting current density, as

RMT,CL = coth(Φ⋅sqrt(4πRρK)) / sqrt(4πRρ⋅Dion⋅DCL)

This model identifies several critical factors that influence the oxygen transport resistance, including the CL thickness, the Pt particle density, and the diffusivities of oxygen in proton conducting phase and in CL voids.

In order to verify this model, a Pt/C catalyst with different Pt:C ratios (ca, 5:5, 3:7 and 1:9 by weight) were fabricated into MEAs and their mass transport resistances were measured with the limiting current method. The I/C ratios and the Pt loadings of the catalyst layer were also varied to investigate the complex interactions of the CL thickness, Pt particle density and CL microstructure (e.g., porosity). The results are compared to the estimates from the above model.
Electrocatalytic Activities and Stabilities of Selenium Based Cobalt-Nickel Binary and Ternary Chalcogenides
Authors: Liu Jiaqi , Zheng Jiwu , Gong Qing , Zhang Tengfei , Cheng Xuan
Published: February 2020

The requirement of precious platinum (Pt) based materials as electrocatalysts and the sluggish kinetics of oxygen reduction reaction (ORR) in a cathode have significantly impeded the commercialization of proton exchange membrane fuel cells. Much effort has been directly made to search for high performance Pt-free cathode catalysts. Chalcogenides are promising alternatives because of their moderate electrocatalytic activities and good selectivity toward ORR in acidic and basic media. The carbon supported binary cobalt selenide (CoSe2/C), nickel selenide (NiSe2/C) and ternary cobalt-nickel selenide (Co-Ni-Se/C) nanoparticles were prepared by a simple microwave synthesis route without or with heat treatment. The microstructure, electrocatalytic activities and stabilities of CoSe2/C, NiSe2/C and Co-Ni-Se/C catalysts were studied in 0.1 mol/L HClO4 or KOH solutions. The single cell performances of the as-prepared catalysts were further investigated and compared.
Application of Platinum Nanoparticles Decorated Needle-Shaped Cobalt for Methanol and Ethanol Oxidation
Authors: Norkus Eugenijus , Zabielaitė Aušrinė , Šimkūnaitė Dijana , Vaičiūnienė Jūratė , Pakštas Vidas , Tamašauskaitė-Tamašiūnaitė Loreta
Published: February 2020

Low-temperature fuel cells operating on methanol or ethanol fuel comprise a promising class alternative sources of energy. Active search for cost-effective and efficient catalysts is still in progress. In this study, the oxidation of methanol and ethanol has been investigated on the needle-shaped cobalt (Coneedle) catalyst decorated with low amounts of platinum nanoparticles (PtNPs). The electrochemical and chemical methods were used for the fabrication of the PtNPs decorated needle-shaped Co catalysts. The electrocatalytic activity of the as-prepared PtNPs-Coneedle catalysts for the oxidation of methanol and ethanol in an alkaline media was evaluated using cyclic voltammetry and chrono-techniques. The data on methanol and ethanol oxidation under different conditions will be presented and discussed.

It has been determined that the decoration of the needle-shaped cobalt catalyst with low amounts of Pt nanoparticles results in enhanced electrocatalytic activity for methanol and ethanol oxidation, compared with that of pure needle-shaped Co and seem to be a promising anode material for direct methanol and ethanol fuel cells.
A Gold-Polyaniline Nanocomposites Catalyst with a Posy Bouquet Structure for Efficient Electrocatalytic Reduction of CO2.
Authors: Vijayakumar Amruthalakshmi , Zhao Yong , Wang Caiyun , Wallace Gordon
Published: February 2020

The concentration of atmospheric CO2 rose up significantly due to the extensive use of fossil fuel as the main energy source since the industrial revolution in 19th century. In 2015, it has already exceeded the upper safety limit of 350 ppm and reached as high as 401.3 ppm [1]. This has been considered as the main cause of global warming, ocean acidification, desertification etc. The electrochemical reduction of CO2 (CO2ER) at room temperature that can produce value-added chemical feedstock and liquid fuels by using the electricity from renewable energy sources is an attractive way for CO2 recycling [2, 3].

Generally, CO2ER suffers from sluggish kinetics and poor selectivity since the CO2 molecule is highly stable that requires high energy to be activated, the electrochemical potential differences between different products are small, and the competitive H2 evolution reaction (HER).Developing selective and efficient catalysts is the key challenge for CO2ER.Gold (Au) is one of the best catalyst investigated for the CO2-to-CO conversion [4, 5]. However, cost and availability limiting its wide applications. Integrating gold with suitable conductive support to form composites can reduce the cost by minimal the usage. Also, these catalysts can deliver remarkably an improved catalytic performance in terms of Columbic efficiency and selectivity due to the synergistic interaction between the metallic catalytic center and conductive support through the enhanced charge transfer by providing σ electron and stabilization of metallic center via weakened binding ability of *CO reaction intermediate [6, 7].

Herein, we synthesized an efficient catalyst, gold-polyaniline (Au-PANI) nanocomposites with a posy bouquet structure by an ecofriendly one-step redox reaction at ambient conditions. This composite displayed a high faradaic efficiency of 85% for CO formation with a high partial current density of 11.6 mA cm-2 at -0.9 V vs. reversible hydrogen electrode (RHE) in 0.1 M KHCO3 aqueous solution, much higher than that for gold nanoparticles or the annealed gold-polyaniline nanocomposites (Au-NC).This work clearly demonstrates the influence of PANI on the CO2ER performance for Au-PANI composite.

References

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CO2 Reduction to CO on Au: Facet Dependent Activity and Selectivity
Authors: Seger Brian , Mezavilla Stefano , Chorkendorff Ib
Published: February 2020

Due to the drastic drop in renewable electricity prices, electrochemical CO2 reduction has received renewed interest. While CO2 reduction can lead to a wide variety of products, almost all go through a CO intermediate, thus understanding the 2 electron transfer reaction of CO2 to CO is important not just for CO production, but also for products such as ethylene, ethanol, methane and others. Au has been shown to be the most active electrocatalyst for CO production, however major fundamental knowledge on this reaction has yet to be discovered. While most works focus on highly active nanostructured Au electrodes, there has yet to be a comprehensive study on the intrinsic electrochemical activity of individual Au facets.

This talk will discuss our work on the electrochemical conversion of CO2 to CO on single crystal Au <100>, <111>, <110>, and <211> facets as well as polycrystalline Au. Our results show a 25 fold difference between the least and most active crystal facets. All facets follow approximately the same Tafel slope between the tested potentials of -0.6 V to -0.8 V vs. RHE. Pb underpotential deposition (UPD) was used to deposit a monolayer of Pb on the Au gold surface to determine surface area. However, the potential at which Pb UPD deposits is facet dependent. By setting a correct potential we could selectively deposit lead on a given facet. While PB UPD favored depositing on the most active sites, we still could gain fundamental catalysis knowledge. On polycrystalline Au, 20% of a monolayer of Pb yielded a 50% decrease in CO production, but only a 30% decrease in H2 production. 50% of a Pb monolayer on Au yielded a 95% decrease in CO production, but only a 50% decrease on H2 production. The decrease in CO production as a function of Pb coverage indicated that not only could we passivate the most active sites, but also that the facet dependent activity was quite different for CO production versus the competing H2 evolution side reaction.

To further utilize Pb UPD to isolate sites we reinvestigated one of our least active facets, Au <111>. As expected, STM images show that our single crystal is not completely flat and there is a small percentage of step sites. We used selective Pb UPD to deposit 4% of a monolayer in the attempts to passivate these sites. This led to a 50% decrease in CO activity, but the same H2 evolution activity. Covering the Au with 15% of a monolayer led to a 90% drop in CO activity, but the same H2 evolution activity. These results suggest that our intrinsic activity of our least active facets is probably much lower than measured and is dominated by a small number of highly active defect sites. While these results focus on Au, no single crystal is defect free. Thus these results may lead us to also question whether there are other situations where the non-optimal facets for a given reaction are actually much less active than originally thought.
Chemical Consequences of Flow- CO2 Reduction in a Microfluidic Flow Cell
Authors: Henckel Danielle A. , Bhargava Saket , Gewirth Andrew A. , Kenis Paul J.A.
Published: February 2020

Transforming CO2 into value added products such as CO, formic acid, alcohols and hydrocarbons is a part of the global scientific effort to reduce atmospheric CO2 levels. In particular, Cu and Cu-based catalysts are the only known materials that can catalyze the reduction of CO2 into C2+ products, although specific product selectivity is an ongoing issue. In this work we utilize a microfluidic flow cell to study the electroreduction of CO2 on Cu. In this system, the electrolyte is flowed over a gas diffusion electrode on which the Cu catalyst has been deposited. The effect of electrolyte flow rate as a lever on the product distribution of CO2 reduction on Cu was investigated. To correlate any effects of product distribution on the local pH of the electrode surface, we utilized in situ Raman spectroscopy to monitor the local pH as a function of electrolyte flow rate and composition.
Sustainable Hydrogen Production Using Water By a Photovoltaic Integrated Electrolyser with Active Area Exceeding 100 cm2
Authors: Calnan Sonya , Kemppainen Erno , Aschbrenner Stefan , Bao Fuxi , Schlatmann Rutger
Published: February 2020

Hydrogen generated by electrochemical water splitting driven by solar energy presents a near zero carbon emission means of energy storage. For the wide scale deployment of this technology, it is necessary to reduce costs of the components by reducing the amount of scarce materials used on one hand on the other hand, simplifying the device design. In this work, a fully integrated photovoltaic driven electrolysis system is designed in which the electrical connection of the device is wholly internal and the two energy conversion components are inseparable. Also transfer of heat from the back of the PV minimodule to the electrolyte is facilitated by thermal contact. Computational fluid dynamics simulations were used to optimise the geometry as well as the feedstock and thermal management in the device. The PV minimodule with a total area of 294 cm², consisted of silicon heterojunction solar cells while the electrolysis cell used 1.0M KOH electrolyte and 100 cm² nickel foam electrodes for water splitting. The hydrogen production efficiency of the entire device was tested under different irradiation and ambient temperature conditions without additional heating. Outdoor tests under irradiation levels of about 500 W/m² recorded hydrogen production rates of reaching 85 µg cm² s-1, corresponding to solar-to-hydrogen conversion efficiencies around 5 %. The use of better catalysts and higher irradiance conditions are expected to contribute to improved device performance.

Figure 1: Photograph of the photovoltaic integrated electrolyser during outdoor tests

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(Invited) Preparing Composite Electrolytes: A Comedy in Two Acts
Authors: Zawodzinski Thomas A.
Published: February 2020

Composites of polymers and inorganic particles are a favorite approach in the literature on preparing electrolytes with desired properties. This is a result of several different aspects. First, such composites are judged to be relatively easy to prepare. Inorganic nanoparticles as well as those such as graphene or carbon nanotubes are readily available. Compounding the materials is often carried out by co-casting from solutions/suspensions.

In this work, we provide a case study of composite formation in two parts. The overall goal was to prepare a proton conducting composite in which the conducting component was provided by sulfonic acid terminated grafts on oxide particles. In the first part, we detail our first attempt at this, in which we used silica particles onto which we synthesized silane grafted alkyl bromides which were then converted into two steps to sulfonic acids. These were prepared in composites with PVDF. This first attempt yielded poor conductors. Investigations suggested poorly connected composite domains. In short, reflection revealed that we did almost everything wrong.

In the second part of the work, we dissected the reasons for failure and sought to create optimal conditions for composite formation with high numbers of charge carriers and good interconnections within the networks of components. This was achieved by using different sulfonate formation chemistry, different particles and, importantly, polymeric components with different levels of functionalization to allow us to tune the interactions between particles and binder. The result of this was a much more effective conductor.

Acknowledgement

We gratefully acknowledge the support of this work by the Department of Energy. The significant contributions of Dr. Berry Decker and Dr. Hossein Ghassemi of Case Western Reserve University are also appreciated.
Optimization of Anion Exchange Membranes Derived from Bacterial Cellulose for Solid-State Supercapacitors
Authors: Guo Xiaojing , Qiao Jinli
Published: February 2020

At present, supercapacitors have received increasing attention, due to its low cost, light-weight, high-performance environmentally-friendly and flexible. Electrolyte has been identified as one of the most influential components in the performance of electrochemical supercapacitors. However, mostly conventional supercapacitors used liquid electrolyte, such as (KOH solution). These liquid electrolytes limit the development of supercapacitors owing to their corrosivity and easy leak. Solid electrolytes not only eliminate leakage problems, but also act as membranes to prevent internal short circuits. Bacterial cellulose (BC) membrane attracted extensive attention, due to the high crystallinity, ultra-fine network structure, high mechanical strength, low cost and good degradability. In this work, Alkaline anion exchange membrane (AAEM) have been developed by using modified BC membrane. The membranes are characterized and tested in detail by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Differential scanning calorimetry (DSC), thermal gravity analysis (TG), mechanical property, ion transport number, AC impedance technique, water uptake, ion exchange capacity (IEC) and swelling ratio to evaluate their applicability in solid-state supercapacitors. The membrane shows a high OH- conductivity of 0.031 S cm-1, excellent stability, and has potential in the application of supercapacitors.
Enhanced Solid Electrolyte Interface (SEI) on Li Metal Surfaces through Catalytic Electrolyte Decomposition
Authors: Lochala Joshua Andrew , Wu Bingbin , Tarverne Tyler , Xiao Jie
Published: February 2020

Lithium metal batteries have seen a rise in attention as the next generation battery is sought. Li metal is considered the “Holy grail” anode material with a high theoretical capacity of 3860 mAh g-1.[1] However, Li metal is unstable during cycling leading to issues with dendrite formation leading to cell short or “dead” Li, and increase in cell impedance due to the excess formation of SEI on the “dead” Li..[2–4] The SEI plays an important role in altering the ion transport which alters the structure evolution of the Li metal anode during repeated cycling. While the understanding of the fundamental properties of the SEI has advanced continuously in recent years, effectively tuning the SEI components, especially the inorganic constituents, is still challenging. In this work, tungsten oxide, WO 3, is found to promote the formation of inorganic salts e.g., LiF/Li2CO3 in SEI layers and thus enhancing the SEI properties allowing for the smoother plating of Li metal. Additionally, WO3 is reduced to W during electrochemical process, the addition of W within the SEI increases the electronic conductivity, reducing the formation of “dead” Li which otherwise is completely wrapped by insulating SEI layers. The possibility of WO3 to catalyze electrolyte decomposition through favored reaction pathway to produce more robust SEI layers is discussed, providing new insights to control the SEI formation on Li metal.

Xu, W., Wang, J., Ding, F., Chen, X., Nasybulin, E., Zhang, Y. and Zhang, J.G., 2014. Energy & Environmental Science, 7(2), pp.513-537.

Pei, A.; Zheng, G.; Shi, F.; Li, Y.; Cui, Y. Nano Lett 2017, 17, 1132–1139.

Wu, B.; Lochala, J.; Taverne, T.; Xiao, J. Nano Energy 2017, 40, 34–41.

Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H. J. Solid State Ionics 2002, 148, 405–416.
A Novel Microbiosensor Microarray for Continuous Ex Vivo Monitoring of Gamma-Aminobutyric Acid in Real-Time
Authors: Hossain Md Imran , Tan Chao , Doughty Philip , Dutta Gaurab , Murray Teresa , Siddiqui Shabnam , Iasemidis Leonidas , Arumugam Prabhu U
Published: February 2020

Gamma-aminobutyric acid(GABA) is the major inhibitory neurotransmitter that is essential for normal brain function. It is involved in multiple neuronal activities, including plasticity, information processing and network synchronization.Abnormal GABA levels result to severe brain disorders and therefore GABA has been the target of a wide range of drug therapeutics. GABA being non-electroactive is challenging to detect in real-time. Here, we report the design and implementation of a GABA microarray probe that operates on a newly conceived principle. It consists of two microbiosensors, one for Glutamate (Glu) and one for GABA detection, modified with glutamate oxidase and GABASE enzymes, respectively. GABA and Glu can be detected continuously in real-time in-vitro and ex-vivo and without the addition of any externally applied reagents. This method yielded higher sensitivity and it was also successfully tested in an adult rat brain slice preparation. These initial results demonstrate that the developed GABA probe has the potential to become powerful neuro-scientific tool that could be employed in the future for in vivo studies. Moreover, we will discuss the recent findings from the optimization of the probe by modifying enzyme concentration and process automation with micro-spotting technique and the changes in the GLU-GABA concentrations in different parts of the brain (thalamus, hippocampus, cortex) for epilepsy disease model.

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Filter Paper Based Electrochemcial Sensor for Selenium Detection in Water
Authors: Devi Pooja , Kumar Praveen
Published: February 2020

The escalated contamination of water resources with inorganic pollutants is a pressing global problem for the ecosystem due to their well-documented negative effects. Over the years, the problem has aggravated due to uncontrolled industrialization, urbanization and the subsequent disturbance to natural resources by mankind. The direct discharge of inorganic pollutants and their geogenic mobilization has caused their elevated concentrations in ground, surface and river water. Selenium is amongst the emerging inorganic pollutants of concern besides other and was neglected earlier by the environmentalist due to their occupancy in other major pollutants and lack of sensitive analytical techniques. It is essentially known as a beneficial element, however, when consumed above a permissible limit, it may lead to devastating acute and chronic health effects. With the advancement made in paper analytical devices, we herein present for the first time the in-situ prepared flexible electrodes from “lab grade filter paper” for selenium sensing in water with high selectivity and sensitivity. The paper electrode are modified with nanostructured materials (metallic nanoparticles) to introduce conductivity, and thereafter utilized as a transduction platform in anodic stripping voltametric based detection of selenium. The flexible paper electrodes are also studied for their structural, compositional and electrochemical characteristic. A battery of ions are tested under competitive and comparative performance evaluation of fabricated sensor electrodes to realize their practical applications in real water samples. The analytical performance of the paper sensor is also validated against ion chromatography reference technique. The designed sensor electrode demonstrate a wide detection capability of 5-1000 ppb, high sensitivity, and excellent detection limit <10 ppb.