# Materials for Energy Applications

• Atharva Sahasrabudhe asked a question:
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.

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
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

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

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.

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.

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.

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

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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

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.

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.

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 .

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.

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?
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].
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.
• Azrol Kassim asked a question:
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.
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.
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 .
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!
Is it possible to theoretically calculate a CV curve for a capacitor model?
Is there any method by which we can get the cyclic voltammetry curve (CV curve)
theoretically?
Alberto Battistel · Ruhr-Universität Bochum
if you want to simulate the CV of a capacitor, you just need to check the equations in wikipedia about capacitor. Once you have the I-V relation, just plug in a potential ramp up and down. It is rather easy. with only a C/R system the CV comes a kind of rectangle. This becomes larger and larger increasing the scan rate.
What is the most current catalyst suitable for fuel cell purposes?
I need a suitable catalyst with high performance towards oxidation of glycerol.
Can anyone tell me about the role of heteroatoms (S, N) during carbon dissolution in a metal matrix (Fe, Ni etc)?
Some of the metals like Fe, Ni have the carbon dissolution property. In such case if we use N-doped graphene or S-doped graphene, the present heteroatom will affect the carbon dissolution property in Ni or Fe.
Vishal Mahesh Dhavale · CSIR - National Chemical Laboratory, Pune
Thanks for the clue. However, the carbon adsorption and dissolution are the simultaneous process and depend on the plane energy. However, is the hetro atom will helps to trigger the same. If anybody have such reference. Please give me the links, if possible.
• Subrata Ghosh asked a question:
How the mass of carbon nanowalls/vertical graphene can be calculated for specific capacitance measurement?
Carbon nanowalls/vertical graphene grow vertically on substrates. To calculate the specific capacitance from cyclic voltammetry measurement, I wanted to know how the mass of the samples can be calculated. Can someone provide any reference regarding that?
What is the theoretical density of Ca3Co4O9 and Zn0,98Al0,02O?
In the frame of my internship, I'm looking for the theoretical density of Ca3Co4O9 and Zn0,98Al0,02O.
Nuno Vitorino · University of Aveiro
Dear Ayoub
For Ca3Co4O9 theoretical density see this paper...
Nuno
Can anyone suggest a method to synthesize of Pt/CNTs nanocomposite?
.
BALAMURUGAN Matheswaran · Sona College of Technology
Microwave assisted synthesis of Pt/CNT nanocomposite is one of the best non toxic, environment friendly grren method. Hereby, one of the best reference article is

Weimin Zhang, Jun Chen, Gerhard F. Swiegers, Zi-Feng Ma and Gordon G. Wallace, “Microwave-assisted synthesis of Pt/CNT nanocomposite electrocatalysts for PEM fuel cells”. Nanoscale, 2010,2, 282-286 (DOI: 10.1039/B9NR00140A)
How can I identify specific phase of WO3 from XRD?
Since the intense 2 theta angles from WO3 XRD peaks seems similar for monoclinic, orthorhombic, and tetragonal phases, how can they be distinguished? is there any specific observation for identification or distinguishing?
Are they similar in intensity? Check with simulations!
• Andreas Hess asked a question:
What are the concentration and temperature dependent electrolyte properties of commercial SelectiLyte LP40?
I am interested in a full set of transport properties for the LiPF6 based electrolyte SelectiLyte LP40 from Merck / BASF analogously to the outstanding work of Valoen and Reimers (J. Electrochem. Soc. 152, A882, (2005)).

Are there any data available?

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Development and Characterization of Metallic and Ceramic Materials for Energy Applications