Materials for Energy Applications

Materials for Energy Applications

  • Deepak Sridhar added an answer:
    How can I reduce a large iR drop in a nickel carbon based supercapacitor?

    Hello everyone, 

    I am doing a galvanostatic charge discharge using the Gamry Poteniostat with a voltage window from 0-0.5 V and 3 electrode setup. When I charge my electrode it takes about 2000 seconds to reach 0.5 V however, it discharges either in 60-120 seconds. The iR drop is about 0.2 V which is pretty high. When I test it at a higher current density the discharge is in milli seconds. I would like to know how I should reduce the iR drop? I tried various concentration of electrolytes from 0.5 M- 6 M KOH but it still shows the drop. The ESR of the electrode is about 4 Ohms which is high. 

    Additionally, I would like to know what program in Gamry has to be used to study the effect of CD on Charge discharge behaviour? I use the Cyclic Charge discharge and calculate the specific capacitance. Is there anyother program that should be used?

    Thanks,

    Haritha

    As Dr. Samaras has commented, your composition of the electrode will play a role in deciding about your IR drop. Your electrolyte, separator will also play a role. 

    best

  • Ahmed A. Farghaly added an answer:
    What is the best substrate for supercapacitor application?

    I am trying to put MnO2/C composite on Al foil, however, the foil is getting damaged after couple of days. Please suggest me some alternate.

    Ahmed A. Farghaly · Virginia Commonwealth University

    Nickel foam is a perfect. I am using it. Some scientists are using Ti foam, graphit/carbon paper or depositing the material over GCE. Good luck 

  • Jason Mclafferty added an answer:
    From where does the electron come in the Oxygen Reduction Reaction?

    When we assemble a full fuel cell, electron comes from the hydrogen oxidation.

    I don't understand  when we study only Oxygen reduction reaction, in a 3-electrode set-up , from where electrons come for that which we calculate from K-L plots??

    Jason Mclafferty · Final Coat, Inc.

    I think what Juan Casado said explains your question regarding the flow of current being in the direction opposite of electrons.  As he says, in electronics and electrical circuits, "conventional current" is taken as the flow of positive charge.  It gets confusing in electrochemistry, because the definition of anode and cathode are referred to the flow of electrons.  This makes it more complicated to understand the interfacing of electronics and electrochemical cells - you have to be careful with the "book-keeping."

    To build on what other said, the potentiostat is moving electrons from the counter electrode to the working electrode or vice versa (through the wires and potentiostat circuit), depending on the reactions occurring.  For example, in your case, the working electrode is supporting a cathodic reaction.  The conservation of charge dictates that the electrons have to be supplied quantitatively by another reaction.  This reaction occurs at the counter electrode.  So for a cathodic reaction at the working electrode, there is an anodic reaction at the counter electrode.  The electrons flow through the potentiostat circuit from the counter electrode to the working electrode and ions move through the electrolyte to enforce electroneutrality in the solution.  So there are two kinds of current - current through the external circuit (wires and potentiostat) and current through the electrolyte.  If you remove one of these paths - no current flows and you have no electrochemical reactions.

  • Ioannis Samaras added an answer:
    Can one use a Cu foam/foil/plate as current collector for testing super-capacitor electrode loaded with Ni(OH)2?

    Hi everyone,

    I found most reports about nickel hydroxide / oxide electrodes said that they used Ni foam as the current collector. Can one use a copper foam or foil instead for testing Ni hydroxide/oxide electrodes in alkaline solution? I found this an issue because Ni foam contributes quite a lot in the scanned potential range (0-0.4V) and shows significant redox peaks.

    Thanks.

    Ioannis Samaras · Aristotle University of Thessaloniki

    An alternative is Titanium Foam, "stable" in alkaline media.

  • Francis Salzano added an answer:
    Can two dimensional materials be used as electrolytes of fuel cell?

    One question about solid state fuel cell: Can the van der waals heterostructure be used as electrolyte of fuel cell? In other words, van der waals heterostructure is impermeable or permeable to proton or Oxygen ion?

    Francis Salzano · Brookhaven National Laboratory

    Please supply more information.

  • Subramanian Ramachandran added an answer:
    What kind of coolant for hydrogen storage in metal hydrides should I use?

    The use of a coolant is necessary to regulate temperature in hydrogen storage tank based on metal hydrides. What kind of coolant is more efficient and most used actually?

    Subramanian Ramachandran · University of Washington Bothell

    Hi, based on my experience, for transition metal hydrides with enthalpy of absorption about 30kJ/mol H2, water as a coolant worked well in keeping the temperature constant during exothermic hydriding process as well during the endothermic dehydriding process. . However, proper designing of the heat and mass transfer aspect is important.

  • Tanujjal Bora added an answer:
    What is the purpose of uniform thickness of titania films in Dssc? What should be the thickness value?

    what is the good thickness value ?

  • Tsvetanka Babeva added an answer:
    How can one obtain pure V2O5 films by the sol-gel method using vanadium tri-isopropoxide?

    I have prepared V2O5 films by sol-gel method using vanadium isopropoxide. The calculated extinction coefficient decreases with wavelength in the range 400-550, have a minimum around 550 nm and starts to increase for wavelength greater than 550 nm. Is it possible some other oxide to be presented in the film? How to obtain pure V2O5 phase.

    Tsvetanka Babeva · Bulgarian Academy of Sciences

    Thank you very much Dr. Carlos Araújo Queiroz! I will try to use acetone. Just to mention that it is not possible to use water with VTIP because even very small amounts lead to precipitation. Till now we have obtained  clear sol only using isopropanol alchohol. Even the usage of ethanol leads to the same effect as using water. The problem is that the deposited thin films have a relevent absorption that lead us to the conclusion that mixed oxides exist.

  • Zol Bahri Razali added an answer:
    What are the competing technologies of shape memory polymers (SMP)?
    The applications of SMP in consumer durable has been very limited. No real applications can be found despite the advantages of SMP. I observed that there have been very less awareness on SMP among the decision makers (e.g. designer, product engineers) in the industry. I believe certain technology has been favored over SMP (for instance mechanical actuators) because of specific factors.
    my questions is: can anyone kindly provide me examples of competing technologies of SMP in any application area.
    Zol Bahri Razali · Universiti Malaysia Perlis

    Please visit to this journal

    http://onlinelibrary.wiley.com/doi/10.1002/1521-3773(20020617)41:12%3C2034::AID-ANIE2034%3E3.0.CO;2-M/abstract;jsessionid=E1A3E7B28045B5C7D677D911BBA1FBCE.f02t03?deniedAccessCustomisedMessage=&userIsAuthenticated=false

  • Francesco Lufrano added an answer:
    In asymmetric supercapacitors, metal oxides are used as which type of electrode? And what about reduced graphene oxide?

    (Cathode and Positive) or (Cathode and Negative) or (Anode and Positive) or (Anode and Negative)?

    Francesco Lufrano · National Research Council

    For Metal oxides as MnOx, they have to be used as the positive electrode and not as negative because are unstable in that side. Therefore, the negative should be done with a carbon material, which can work as both the negative and positive electrode.

  • Arvinder Singh asked a question:
    How can one perform time limited OCP (open circuit potential) measurement in Autolab Nova 1.10 ?

    I want to measure OCP of a supercapacitor device for a time period (say for 10 hours). Is it possible with Autolab Nova 1.10?

    I didn't find options for time limited OCP measurement, however, we have options for d(OCP)/dt limited OCP measurement.

    Thanks

  • Siva Subramanian added an answer:
    How do I measure charge-discharge in a supercapacitor using chronocoulometry ?

    How can I perform charge-discharge measurements on a supercapacitor material in a standard 3 electrode set-up using the Chronocoulometry technique. I am using CHI604D workstation, if that helps. I have come across one article (see link below) that uses this technique for charge-discharge measurements, but the authors have not explained the details of the same. 

    Siva Subramanian · Indian Institute of Technology Madras

    Dear atharva

              As santimoy pointed out electrochemical charge discharge in a supercapacitor can be measured by chronopotentiometry. For further reference kindly have a look with the attached paper.

  • Sai Siddhardha R. S. added an answer:
    How to convert a potential collected with reference to Ag/AgCl to Reversible Hydrogen Electrode?
    I have collect a cyclic voltammetric data by taking Ag/AgCl as the reference electrode. But I want to convert this one to Potential with respect to Reversible Hydrogen Electrode. Please suggest me the required conversion equation. 0.5M H2SO4 was taken as the supporting electrolyte.
    Sai Siddhardha R. S. · Sri Sathya Sai Institute of Higher Learning
    • The general equation for this conversion at any pH using Ag/AgCl reference electrode is:
    • E(RHE) = EAg/AgCl + 0.059 pH + EoAg/AgCl
    • Where EoAg/AgCl = 0.1976 V at 25oC and  E Ag/AgCl is your working potential
  • Mojgan Kouhnavard added an answer:
    Does anyone know how to measure LUMO-HOMO from CV?
    As I searched there are different formula for it which I don't know which one I should use? And what is different between them?

    1) E LUMO=-(E red (onset)+4.4)
    2)E LUMO=-[4.65 V-E red(onset)]
    3)E LUMO=[(E red-E 1/2 (ferrocene)+4.8 ]
    4)E LUMO=-(E red (onset)-4.4)
    Mojgan Kouhnavard · Universiti Teknologi Malaysia

    thanks for your comprehensive reply. it helped a lot, indeed.

  • Mazdak Hashempour added an answer:
    Does anyone have an idea about the adhesion of a carbon paste to Al for supercapacitors?
    One of the methods of electrode preparation for electrochemical capacitors is to cast a paste of active material (mainly containing carbon nanostructures) on a metal sheet (Al or other metallic substrates). However, the adhesion of the carbon layer to current collector is always an issue, especially under the applied electrochemical conditions. The paste components are usually like: Activated carbon+ [CNT or Graphene or pseudocapacitive materials & etc.] + a polymeric binder (PVDF, PTFE) + an organic solvent (NMP).
    So, how can we improve this adhesion?
    Mazdak Hashempour · Politecnico di Milano

    Hi Qamar,

    Nice to hear from you again after Lausanne and thanks for participating the discussion.
    Honestly, we have not focused deeply on the corrosion of Al substrate. We either use the direct growth of active material (mainly CNTs) on Al for supercap (like these papers: Supercapacitor electrodes by direct growth of multi-walled carbon nanotubes on Al: a study of performance versus layer growth evolution AND Growth of carbon nanotubes on aluminium foil for supercapacitors electrodes) or the paste method. In case of growth method, we have not encountered the contact and adhesion problems of the CNTs to Al and so, we have not gone through the corrosion issue though it is definitely worth investigating. Especially, considering the point that our studies have been mainly focused on the material’s capacitive behavior and therefore, we have not gone through long and severe life cycling experiments. Although below 10K cycles the systems works reasonably, in longer cycles, maybe up to 100K, there is no guarantee that it remains as good as it was. So, it should be tried. The potential window in those cases (direct growth) is usually less than 1 V (0.7-0.8 V) and the collector is high purity Al. We didn't try other alloys and we didn't observe corrosion products or color changes on collector or separator. Pitting and other microstructural checks yet remain to be carried out in case we plan to monitor the longer cycling behavior of the system.

    The problem of adhesion however, refers mainly to the paste method where even before starting the electrochemical characterization, the electrodes suffer from delamination and cracking. I have seen some works using special pretreatments on substrate with special conductive adhesives (like Electrodag EB-012) to enhance the adhesion of the paste to the substrate (see the suggestion by Steffen Schlueter in this discussion and his paper: Strategies to Reduce the Resistance Sources on Electrochemical Double Layer Capacitor Electrodes). Moreover, in our work, we do not prepare the active material as a separate film to be put on gold or Al current collector, but we try to cast it on the current collector to make it more realistic in practical point of view and more similar to a supercap electrode. Here is where the problem of delamination and cracking comes up even before the start of the characterization.

    Have a good time

    Mazdak

  • Rasu Muruganantham added an answer:
    How can we improve the conductivity of the olivine structure LiFePO4 with other transition elements?
    Do you think that the substitution of Fe in LiFePO4 or doping Mn, Mg, Cr or Co, improves its poor conductivity?
    Rasu Muruganantham · Alagappa University

    If You doped with other metals on LiFePO4 , I suggest the conductivity improved depends on your dopent elements but c/d performance definitely changed the pure LFP. so surface modification is best way to improve the conductivity as well as C/D performances.

  • Daniel Marinha added an answer:
    If a material is not only ionic conductive, but also electric conductive, how to measure its ionic conductivity and electric conductivity separately?
    I want to measure the electric and ionic conductance of slurry.
    Daniel Marinha · Saint-Gobain

    I would be very careful in following Huggins simplistic method to determine mixed conductivity by impedance spectroscopy. see j. maier's work on the topic. 

  • Michael Dubrovsky added an answer:
    Can someone suggest a battery chemistry which has equilibrium concentrations very sensitive to temperature?
    See this google drawing I made to illustrate a hypothetical battery system where the equilibrium point (where battery is considered "dead") changes with temperature.

    https://docs.google.com/drawings/d/1zeGpgjE4uTnBlAtCTwmSVAZP0u7jMgQ3SkqdguFCX-o/edit?usp=sharing

    I am looking for battery chemistry where this shift is dramatic. Common/cheap battery chemistry preferred but exotic ones would be interesting as well.

    Also, would take a suggestion for a good reference which provides experimental data on the dV curves as they relate to T for various battery reactions.

    _________

    In theory this shift would be dramatic in battery chemistries that have high entropy difference between product/reactants. I can think of some examples but interested to see what others think/know empirically.
    Michael Dubrovsky · State University of New York College of Environmental Science and Forestry

    ?

  • Subbukalai Vijayakumar added an answer:
    Could anyone tell me how can to measure IR drop?
    I want to measure IR drop. Is there a way to measure it from galvanostatic charge/dicharge curve?
    Subbukalai Vijayakumar · University of Ulsan

    Charge-discharge is time against potential diagram.  Straight line part in the discharge curve from maximum potential give the value of IR drop.  If you want to measure IR drop means, In discharge part

    1. note down the maximum potential and time (s) - V1

     Consider max potential is 1 V at 60 s.

    2. Note down the minimum potential in the same time -V2

     low potential in 60 s is less then 1 V, say 0.98 V 

    The difference between V1 and V2 is IR drop. So 1 V - 0.98 V = 0.02 V is IR drop

  • Mazdak Hashempour added an answer:
    What is the difference of Internal Resistance (Ri) & Equivalent Series Resistance (ESR) in the context of supercapacitors’ resistance & power density?

    Equivalent Series Resistance (ESR) and Internal Resistance (Ri) are two measures for the evaluation of a supercapacitors' resistance. The former is evaluated through the electrochemical impedance spectroscopy (EIS) and the latter, through the cyclic charge-discharge (CCD) experiment and the potential drop on current peak at the initiation of the discharge. Disregarding the obvious distinction in the method used for their measurement/evaluation, what is their difference (if any)?


    Basically, the sources of the resistance in a supercapacitor are the same independent from the method used to measure and quantify them:
    The intrinsic resistance of the electrolyte (R electrolyte), diffusion resistance of the electrolyte among and into the porous structure of the active material (R diff), contact resistance between the active material and the current collector (R cont) are the most well-known sources of the resistance.
    From the other hand, ESR and Ri, to the best of my knowledge, are intended to measure the same things. So, as far as the global magnitude of the cell resistance is concerned (like in the case of power density estimation, where, the specific contributions of the different components to the global cell resistance are not important, but their summation instead) why should ESR and Ri be different? and if they are, what is the criterion for the use of either ESR or Ri ? There is no reliable agreement on this in the literature (some use ESR and some other the Ri).

    Mazdak Hashempour · Politecnico di Milano

    Hi Xingfei,

    Yes, generally EIS is a more complicated method compared to the other technique and delicate elaborations are required to extract the data (eg., ESR) out of it. But about the precision and accuracy and reliability of the data (I mean in this case, for the overall resistance) I am not sure which one could be better.

  • Debarati roy chowdhury added an answer:
    Can I do chronopotentiometry in potentiostat using a CHi 760d model?

    I am doing it for a supercapacitor study. I got the data but I am not sure whether it is acceptable or not. Should I use galvonostatic charging discharging? I am attatching two of my chronopotentiometry data. Please help me.

    Debarati roy chowdhury · Indian Institute of Science Education and Research Bhopal

    Dear K.P. thank you. I am really grateful to you. In that paper they have done without separator. Now I can do chronopotentiometry in potentiostat.

     

  • Mustafa Kamal added an answer:
    How do we calculate d-spaces from SAED pattern?
    I have taken SAED pattern of my Titania sample. It is showing that the sample is polycrystalline with clear boundaries. I calculated d-spaces using Image-J, but the d-spaces values are not matching with the XRD pattern? I attached the electron diffraction images below. Could you suggest me how to calculate or how to match d values with XRD?
    Mustafa Kamal · Mansoura University ,Al Mansurah ,Egypt

    The interpretation and indexing of spot patterns from single - crystal are nearly always carried out using the concept of the reciprocal lattice originally by Ewald and Von Laue. The reciprocal lattice is one composed of a system of points , each of which represents a reflecting plane in the crystal and has the same indices as the corresponding reflecting plane.

    dr = Camera constant . R it is easy to measure directly from the phtographic plate and once r is indexed , camera constant can be established  . This is not eadsy to do if bthe structure is not Known  . The Camera Constant will also vary with the lens current used so that camera constant must be worked out of each pattern that is obtained .

    Once Camera Constant is known for the microscope the diffraction patterns may quickly indexed simply by dividing Camera Constant with the measured distances r of the spots from the origin in this way d- spacings are obtained directly .

  • Matthew Monari Ombaba added an answer:
    What initial charge/discharge rates should I use for Li-ion pouch cells?
    I am making "coffee bag" batteries, aka pouch cell batteries. The cathode and anode are LiFePO4(Al) and CMS graphite(Cu), respectively. The electrolyte is 1M LiPF6 in ethylene carbonate, dimethyl carbonate and diethyl carbonate. All materials are bought as prepared.

    I made a 3 cell battery that should have ~74 mAh capacity. I originally reached this capacity, but the capacity is dropping with each subsequent charging/discharging cycle. The charging cycles are as follows:

    Constant Current Charge - 8.2 mA up to 4.0 V
    Constant Voltage Charge - 4.0 V until 0.1 mA
    Rest - 5 min
    Constant Current Discharge - 8.2 mA until 2.5 V
    Rest - 2 min

    The rate is ~ 0.11C.

    Why would the capacity be dropping? Water contamination? Gas build up?

    Thank you.
    Matthew Monari Ombaba · University of California, Davis

    A rule of thumb when characterizing most batteries is to do a C/20 charge- discharge cycles. Normally, commerical batteries use this cycles to determine their  capacities. I would stick to that.  From my experience, dont work in a Nitrogen filled  glovebox if you want to avoid errors. I would keep a potential window of between 1-3.6V. Hope this helps.

  • Juan Casado added an answer:
    Is it time to think other catalyst than TiO2 for water splitting?
    There are so many papers on water splitting using TiO2 based photocatalysts. However, the yields of hydrogen production are very low. I think some compositions other than the trends need to be synthesised and tested...I would like to have your opinion on this and would like to welcome your views.
    Juan Casado · Autonomous University of Barcelona
    Anwar, Any data on the stability of the system you have worked in?
  • Manohar Sehgal added an answer:
    Can we conclude that the performance of Indium tin oxide nanoparticles are better than bare tin oxide nanoparticles for various applications?
    Comparison between ITO and TO
    Manohar Sehgal · DAV College Jalandhar
    The superiority of[ ITO] over [TO] can well be authenticated from the following two references .In fact the above answer gave a “resume” of these two references for your kind perusal:

    [A]Journal of Nanoparticle Research 12(7):2597-2603].
    [B] J Am Chem Soc. 2009 Dec 16;131(49):17736-7].
  • Morteza Karimzadeh added an answer:
    Which are the best sulphurizing reagents for SILAR deposition?
    I'm thinking about Na2S, but I was wondering if using any organic reagent like thiourea (it should thermally decompose at low temperatures) would be suitable too? Thanks
    Morteza Karimzadeh · Isfahan University of Technology
    It may be possible to use KSCN to do sulphurizing. Such compounds can also be applicable in higher temperatures.
  • Chunhua Cui added an answer:
    Does anyone know the reported highest photocurrent of doped/non-doped hematite Fe2O3 photoanode without introduction of any cocatalysts by Vis light?
    It is driven by visible light above 400 nm. One reference please and I would like to mention and cite it.
    Chunhua Cui · University of Zurich
    Thanks, João.
  • Alaa J Mahrath added an answer:
    Is there a simple way of converting chloride to alkoxide?
    I have some chlorides (zirconium, titanium and silicon) and would like a simple way to convert them into alkoxide? Is it possible? Is the reaction dangerous? If you can provide me some information or literature, it will be very welcome.
    Alaa J Mahrath · University of Babylon
    This is depend on what you want to do after alkoxide formation. as you know in most cases the alkoxide can be formed by rxn of metal group (I or II) elements with alcohol this type is highly reactive ( strong base).if you look at IE of sodium , zirconium and magnesium (5.1 ,6.6 and 7.6) ev. so the Zr can be converted to alkoxide .
  • Christopher F Buurma added an answer:
    What are the alternatives and workarounds for Solar Simulators in DSSC Research?
    I am involved with research on Dye - Sensitised Solar Cells (DSSCs) at an institution which does not currently have (and presumably cannot afford) a solar light simulator. I was wondering if there are feasible alternatives to obtaining a simulator, and possible implications on the quality of the research and data obtained. We had considered calibrating a Xenon lamp to obtain 1000W/m^2 equivalent light intensity, but the logistics involved in designing a working testbed would probably be a diversion from the main focus of the research.

    The institution is a University located in the Tropics, and has clear, sunny weather for most of the year, so extended data collection (via datalogger) might be a last resort alternative.
    Christopher F Buurma · Epir Technologies Inc.
    I will also warn that you should invest time/effort into properly calibrating and controlling your light source. You can save hours, days or weeks of wasted time by having reproducible and representative data. Without a proper light source there are techniques to use other light sources and a known QE curve for your device. These spectral matching methods are often used as a corrective measure on near-solar simulated light.
    Good luck!

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