- V.ladimir Nikolaevich. Fateev added an answer:What is the best binder to fabricate membrane-electrode assemblies for HT-PEMFCs using PBI-based proton-exchange membranes?While it is well-known that the electrodes for HT-PEMFCs generally include Teflon as the binder (originally added to the electrode inks in suspension form), suppliers provide several different types of Teflon suspensions, including a variety of surfactants (both ionic and non-ionic). Does the type of surfactant make a difference? If yes, how? What's the best Teflon suspension to fabricate electrodes for HT-PEMFCs?
I suppose that teflon is OK but without surfactants - they can act as a catalyst poison.Following
- Abudukeremu Kadier added an answer:What is best chemical way to detect hydrogen evolution?Hi,
I'm developing a new reaction that hydrogen is generated as key product. I want to experimentally show that hydrogen is generated. My idea is to connect the Schlenk tube (which the hydrogen evolution reaction undergoes) with other reaction which requires the hydrogen gas as reactant. Perhaps something like Rh catalyzed hydrogenation reaction. Could you give me a good candidate for this type of 'hydrogen detecting reaction'?
GC and GC-MS.Following
- Ran Hong added an answer:Suppose an electron loses all its energy and falls into a nucleus, what will happen?My assumption is that energy will be released and only neutrons will exist.
If we only allow EM interaction, the electron can never lose all its kinetic energy. It will stay in its ground state (like a hydrogen atom at ground state) forever. It does spend time inside the nucleus, since the wave function has non zero value there. If weak interaction is allowed, and for some nucleus, electron capture can happen. It will be converted into a e-neutrino.Following
- Lionel Flandin added an answer:Should I use TGA or XPS for determining the Pt loading of carbon support in PEM & DM fuel cells?After the catalyst synthesis and decoration of the support materials (carbon species in this case decorated with Pt nano-particles, by any method), one needs to know “how much” Pt is there to take it into account for normalizing the electrochemical results by the mass of Pt catalyst. One reliable and mostly used method is the TGA to determine the Pt fraction of the “support-catalyst” system, right after the synthesis of the material (washing & drying of course considered).
However, this is not exactly when this “support-catalyst” system is electrochemically characterized, but there are also intermediate steps such as preparation of the slurry or paste for casting on the glassy carbon electrode which involves a lot of sonication. Since this sonication could give rise to some of Pt nano-particles come off the support, the final loading could be less than what measured by the primary TGA.
Another necessary step to characterize the behavior of the “support-catalyst” system is the surface chemistry that is assessed by the XPS. Usually the prepared slurry can be drop-cast on a XPS neutral substrate (e.g., Si wafer) and analyzed. This XPS can also give a quantitative measurement of the materials and their oxidation states. But since it is done after the sonication, the probably disintegrated Pt particles can be assumed to be put out of the total sum (to avoid any destructive interference in the final XPS results, nafion can be added to the slurry after the sample collection for XPS).
So, the question is if one can rely on this XPS result for Pt loading instead of TGA.
We've used TGA for this purpose during the last couple of years. It works fine. It remains the most efficient way, although the standard error is rather high.
- Rina Dao added an answer:What is the relation of SOMO energy and the reaction barrier of hydrogen atom transfer?I am working on this reaction: R-H + X· → R· + X-H
I'm curious about the relationship of the SOMO energy of the abstracting radical and the reaction barrier. The radical SOMO is somewhere between the R-H LUMO and HOMO, when X· is electrophilic, SOMO energy is more close to HOMO. because the interaction between the radical SOMO and the R-H HOMO helps to lower the overall barrier, so the lower the radical SOMO evergy, the better. But, is there a theory, maybe, supporting this viewpoint? Is there a numerical relationship between the SOMO energy and the barrier?
Here is the answer they gave me on computational chemistry list. He said the barrier and orbital gap are related in, eg. Diels Alder reaction. So, is it true in hydrogen abstraction reaction? I am really confused. Please help me.
(by Marcel Swart from CCL)
When you look into the literature of Frontier MO for e.g. Diels-Alder reaction,you can see a good correlation (I seem to remember between the
HOMO(diene)-LUMO(dienophile) and the reaction barrier). And this
was also related to the change in barrier and MO-levels when electron-
withdrawing or -donating groups are added.
To Prof. Peter Daminan Jarowski
I have read both FMOT and PMOT, but how to mix them? The gap of the interacting orbital might be considered as the driving force ? Could you perhaps give an example paper or anything ?Following
- Dhiraj K. Mahajan added an answer:Does anyone have any knowledge on hydrogen pressure chambers for fatigue testing?
At our institute, we are planning to install a fatigue testing facility for metals under pressurised hydrogen.
While I can find guidelines on security concerns involving such kind of experiments. I was not able to find a company that can help install such facility.
In case some one can provide some link or reference to such organization/company, it will be extremely helpful.
Thanks in advance,
Dhiraj K. Mahajan
IIT Ropar, India
Thank you David for your reply.
I have seen the design in the book earlier.
However, I am intersted to get in contact with a company that can help to build something similar at my institute.
- Chandrasekhar Kuppam added an answer:How do you see Hydrogen as next generation biofuel?I have read that hydrogen (generated by microorganisms) can be used as fuel for automobiles but its overproduction and rough handling may prove toxic and even lethal.
What are the prospects in using hydrogen as fuel or biofuel? Would it be safe, non toxic and economical? What are the main parameters that need to be checked for its production and application?
Hydrogen is a fuel of the future because it has a excessive energy density, nearly 3 times that of petrol or diesel, and hence its use produces only H2O instead of greenhouse gases and other exhaust pollutants. Moreover, using petrol and diesel in combustion engines waste at least two thirds of the energy in the fuel, whereas hydrogen can be used in fuel cells, which are about twice as efficient, so much more of the fuel’s energy is put to good use and less fuel is needed.
Nevertheless, H2 is not an energy source but an energy carrier; it’s a useful way of carrying energy from renewable sources such as sun, wind and water to valuable applications such as a car. Many types of microbe can convert renewable energy sources into H2.
Biohydrogen is an example of an advanced biofuel (or third generation biofuel). In advanced biofuel technologies, microbes are grown in special bioreactors and provided with the energy and nutrients that they need including, sunlight, waste organic material, CO2 from the air or from conventional gas plants. As they grow the microbes produce the biofuel.
However there are some parameters/factors affecting biological hydrogen production as follows...
3) Hydrogen Partial Pressure
4) Volatile Fatty Acid (VFA)
6) Metal Ions
7) Hydraulic Retention Time (HRT) etc.....Following
- Maxim Belkin added an answer:How can I go about visualizing first hydration layer oxygen and hydrogen average density?I have an MD trajectory file in TIP3P water. I want to use the trajectory to create a 3D visualization of the density map (or average polarization density whichever is easier) of the Oxygen and Hydrogen of the closest water molecules to the molecular surface. How do I go about it? I saw something in chimera tutorial but got confused. Something like the figure 2 in this article http://pubs.acs.org/doi/abs/10.1021/jp709958f is what I need.
Figure 2 in that paper is density plot. You can easily do this type of analysis in VMD. To get density map, use the VolMap plugin. In "Selection" specify "water and oxygen" (or "water and hydrogen"), volmap type - "density", weights - "mass", check the box to average results for the entire trajectory, and output results to a file. You may also increase a bit the default values in the "atom size" field to get slightly smoother-looking results and in the "resolution" field to speed up calculations (at least for the initial test run). The result will be a 3D map, that you can visualize nicely in VMD.
If you want to get g(r), use the GofRGUI plugin. Don't use GPU-accelerated version for now (or, at least, make sure to compare the results to the CPU version).
In VMD, you can access both of these plugins under Extensions->Analysis menu. (The latter is called "Radial Pair Distribution Function g(r)" there).
- Dave Modeste added an answer:What would be the most suitable method to separate a mixture of gases containing H2, H2O and HCl?The mixture of gases contains about 5vol.% of HCl, 25-30vol.% of hydrogen (H2), and the rest is water steam (65-70vol.%). I want to separate hydrogen to use it afterwards for power generation (i. e. in a fuel cell). I think one of the recommendations is using certain types of membranes, any ideas?
The mixture of gases is coming from the exothermic reaction between Al(OH)3 and HCl (mainly), carried out during the preparation of PAC (aluminium polychloride) and ACH (aluminium hydroxide).A membrane separation approach is an option depending on the operating conditions. Another alternative is an absorber, using a packed bed with water, or a weak NaOH solution as the absorbent. As long as the incoming water is cool enough, and you have a means to remove the heat of absorption due to HCL, you should be able to get a fairly clean H2 stream overhead, and some aqueous HCl solution if water is the absorbent. This approach can be evaluated using ChemCad as mentioned earlier or Aspen Plus, or Pro II. Key issue for the separation approach may be the capital cost of a separation column vs a membrane separation unit. There may be other contributing factors that may affect the decision; things like operating costs, and the reliability of membrane separation vs absorption.Following
- Arun Siddarth added an answer:How can I obtain a high-performance photocatalytic system for hydrogen generation from water splitting?Water splitting to generate hydrogen production.A large amount of research into Photocatalytic and Photoelectrochemical water splitting has been conducted, high efficiency systems are already being developed. Water splitting is an uphill four electron-hole task, and There are a number of factors that limit efficiency. Most significant factors are 1. Electron-hole recombination, 2. Stability of the Photo-catalyst and 3. Light absorption across a broader range of the solar spectrum. These problems have been dealt with in two approaches, and have resulted in significant improvements in stability.
1. Combination of a light absorbing semiconductor with a water oxidation/Hydrogen evolution catalyst. In addition to playing its role in water oxidation/reduction, an effectively designed catalyst prevents electron hole recombination, increasing the life time of excited charge carriers. This increases the photocurrent, and decreases the activation energy barrier (or overpotential in an electrochemical sense). This basically increases Applied bias photon-to-current efficiency (ABPE) due to reduced bias requirement for PEC water splitting (Or increases the Solar to hydrogen conversion- STH efficiency in the case of wireless photocatalytic systems). This approach is most suitable for water oxidation, the biggest barrier for water splitting. However, these systems cam be expanded for water reduction as well, basically using something like Cu2O combined with a molecular HER catalyst. The Nocera lab at MIT has contributed a lot to development of semiconductor catalyst systems.
2. The photocatalyst must use the solar spectrum to get 4 electrons and holes that stay apart and do not recombine within minuscule duration. Use of multiple light absorbers and tandem cells (combined water oxidation/reduction photocatalysts in a singe cell as two discrete compartments) is a very good approach. The work performed by Prof. Gratzel and his team at EPFL has produced excellent results.
You may want to refer to these books for good info (link provided)
1. Photoelectrochemical Hydrogen production (Gratzel)
2. Photoelectrochemical Water Splitting : Materials, Processes and Architectures (Hans-Joachim Lewerenz, Laurie Peter)
Also for practical research protocols and experimental approaches on water splitting, the following book released by DOE will come in handy (link provided)
1. Photoelectrochemical Water Splitting.Following
- 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.Anwar, Any data on the stability of the system you have worked in?Following
- Wang Fuqiang added an answer:How to successfully convert water into fuel using sunlight and earth abundant materials?What are the options for:
Water into hydrogen, oxygen, or low carbon fuel?
At what cost, materials, infrastructure, etc?Solar thermo-chemical reactions with the consideration of spectral wave length.Following
- Wang Chun asked a question:Does Silicate-1 still have hydrophobicity under high pressure and temperature condition?I read that silicate-1 usually has good hydrophobicity under certain conditions. As we know, H2O is gas phase under high temperature and pressure condition. Thus, I would like to know whether the silicate-1 still has good hydrophobicity or not. Some recommended references would be useful.Following
- Kien-Cuong Pham added an answer:Why does the voltage of fuel cells decrease when we increase the load (i.e. current)?As an open circuit voltage of individual cell is about 1 volt (theoretically 1.23 V). When we apply the load then there is a sudden drop in voltage decreasing gradually by increasing the load (current). What happen within the cell? Is it due to decrease the reaction site available to the reactant gases? Or ability of proton conducting membrane? Or due to there catalyst activity?Dear Anjum,
There are three major loss factors in a fuel cell, including kinetic loss, ohmic loss and mass transfer loss. I assume that you are interested in PEM fuel cell.
Firstly, at the low load region, you will see a large drop of voltage from a theoretical 1.23V to about 0.8V or so. This is the kinetic loss due to the very slow reaction kinetic of oxygen reduction in the cathode side. This in turn requires a large overpotential (voltage loss) to drive any practical current density. Pt is currently the best commercial catalyst, but this is still not efficient enough. In this region, the ohmic loss and mass transfer loss are not significant.
Then with increasing load, while the kinetic loss continues taking place, there is an ohmic loss adding in as well. This is due to the internal resistance of the fuel cell, mainly from the PEM membrane.
Lastly, at high current density, you may see another quick drop of voltage. This is due to the mass transport issue that the reactants cannot be delivered to the catalyst sites quickly enough, either due to the low porosity of the electrode, or due to water flooding, or anything that prevents the reactant flows.
Hope it helps.Following
- Wan Ahmad Najmi Wan Mohamed added an answer:How can we handle the flooding issue in large PEM fuel cell stack?There is durability issue of PEM fuel cells due to flooding problem. When we operate the cells above 500 watts there is a big voltage drop. This may due to dryness or flooding on the individual cells.In my experience with large stacks (single cell active area >200 cm2) the operational key to minimize flooding is constant purging on both sides. But expect a greater loss in fuel usage.Following
- Partha Sarathy added an answer:What is the best possible way to quantify H2 gas concentration in a mixture of gases?Assuming no use of any analytical instrument is to be performed. Any idea of using simple method without the need of any instrument is highly welcome. For information, gas mixture may contain CH4,CO,CO2,H2,H2O.Http://www.ncbi.nlm.nih.gov/pubmed/9670345
- Taib Iskandar Mohamad added an answer:How can I design the cam for inlet and exhaust if I want to convert single cylinder SI engine to hydrogen engine?The flame speed of hydrogen is higher than the gasoline and the ignition energy required is very low but the auto ignition temperature of hydrogen is higher than that of gasoline. So in the combustion of the hydrogen, how we can calculate the Lift and Dwell for the both intake and exhaust cam? What changes will be needed in the cam design?The breathing pattern of engine has significant effect on combustion, performance and emission. Engine designs are optimized for specific fuel. Among the optimize parameters are the cam profile. Referring to some characteristics of hydrogen-air reaction it is not easy to give theoretical reference for designing cam because the engine geometry also need to be considered. I would suggest that you use simulation tool with your engine geometry to predict engine response to hydrogen combustion by varying the cam profile. Some useful software include AVL Boost. It is easy to change the cam profile and predict engine performance and emission.Following
- Jorge Morales Pedraza added an answer:What are the other popular applications of hydrogen other than in energy (fuel cell)?I'm looking for possible applications of hydrogen in microchannel system, preferably other than energy applications.A limited number of analytical techniques have been used for measuring hydrogen sulfide in the breath (expired air) . These include gas chromatography coupled with flame ionization detection (GC/FID), gas chromatography coupled with flame photometric detection (GC/FPD), iodometric titration, potentiometry with ion-selective electrodes (ISE), spectrophotometry, and high-performance liquid chromatography (HPLC). Puacz et al. (1995) developed a catalytic method, based on the iodine-azide reaction, for the determination of sulfide in whole human blood. The method involves the generation of hydrogen sulfide in an evolution-absorption apparatus. In addition, the method allows for the determination of sulfide in blood without interference from other sulfur compounds in blood. This method is appropriate for the determination of sulfide in the concentration range of 4–3,000 μg/L. A percent recovery of 98–102% was achieved. Although the accuracy and precision of the catalytic method are comparable to those of the ion-selective electrode method, the catalytic method is simpler, faster, and would be advantageous in serial analysis. Richardson and others developed a method for measuring sulfide in whole blood and feces, which overcomes the problems of viscosity and turbidity that are typical for these types of samples. Turbidity of the sample interferes with colorimetric assays such as methylene blue. In this method, samples are first treated with zinc acetate to trap the sulfide as an insoluble zinc complex. Next, a microdistillation pretreatment is used to release the complexed sulfide into a sodium hydroxide solution. This microdistillation step is coupled to ion chromatography with electron capture detection. A detection limit of 2.5 μmol/L (80 μg/L) and percent recoveries of 92–102% (feces) and 79–102% (blood) were reported. GC/FPD was employed for measuring hydrogen sulfide in human mouth air with a detection limit of 7 ppb (Blanchette and Cooper 1976) and included improvements such as calibration of the system with permeation tubes, use of a variable beam splitter to produce a wide range of vapor concentrations, and the ability to handle samples of limited volume. For occupational measurements of airborne concentrations, NIOSH (1977a) recommended the use of a midget impinger for sampling breathing zone air and the methylene blue/spectrophotometric method for the analysis of hydrogen sulfide. The detection limit was 0.14 ppb. GC/FID has been used for quantifying sulfur volatiles such as hydrogen sulfide in human saliva (Solis and Volpe 1973). This method included microcoulometric titrations and a procedure for incubation of saliva and sampling of headspace sulfur volatile components. The amount of total sulfur volatiles detected in control samples of saliva incubated at 37 °C for 24 hours ranged from 4.55 to 13.13 ppm. Fresh and frozen mouse tissue samples obtained from brain, liver, and kidney have been analyzed for hydrogen sulfide levels by sulfide-derived methylene blue determination using ion-interaction reversed-phase HPLC. This method can quantify nmol/g levels of sulfide. Gas dialysis/ion chromatography with ECD has been utilized for measurement of sulfide in rat brain tissue with 95–99% recovery. The methods most commonly used to detect hydrogen sulfide in environmental samples include GC/FPD, gas chromatography with electron capture detection (GC/ECD), iodometric methods, the methylene blue colorimetric or spectrophotometric method, the spot method using paper or tiles impregnated with lead acetate or mercuric chloride, ion chromatography with conductivity, and potentiometric titration with a sulfide ion-selective electrode. Several methods for determining hydrogen sulfide in air have been investigated. GC/FPD has been widely used for analyses of hydrogen sulfide at levels ranging from 10-11 to 10-8 grams/0.56 mL and for hydrogen sulfide in emissions from tail gas controls units of sulfur recovery plants to a sensitivity of 0.5 ppmv. Sampling of a standard reference (0.055 ppm hydrogen sulfide) with this method resulted in a relative standard deviation of <3%. The sensitivity of hydrogen sulfide detection in air was improved with GC/ECD. The detector operation is based upon the measurement of the current when hydrogen sulfide is electrochemically oxidized at a diffusion electrode. Use of this method resulted in a lower detection limit of 3x10-12 grams hydrogen sulfide and a precision of 0.5%. Analyses were achieved within 2 minutes. GC/FPD has been used to measure hydrogen sulfide that has been removed from air by activated carbon fiber. Activated carbon fiber, made from coal tar, effectively oxidized hydrogen sulfide (200 ppm) to sulfate. Methylene blue techniques have been widely utilized for continuous, quantitative monitoring of hydrogen sulfide in air and are sensitive to hydrogen sulfide concentrations down to approximately 1–3 ppb. This method provides adequate specificity with good accuracy and precision. The amount of sulfide is determined by spectrophotometric or colorimetric measurement of methylene blue. The method has been improved to eliminate the formation of the precipitate cadmium sulfide, which can result in the obstruction of the sampling impinger. Also, the simplified method can be used to measure hydrogen sulfide levels in the viscose rayon industry because it is not as sensitive to carbon disulfide. Limitations of the methylene blue method include potential interferences from light, mercaptans, sulfides, nitrogen dioxide, and sulfur dioxide, and that the system is not portable. Photoacoustic spectroscopy of hydrogen sulfide converted to methylene blue has been demonstrated to yield greater sensitivity than standard spectrophotometric methods. By maximizing instrument response to the 750-nm peak, it was possible to achieve a detection limit of 0.01 μg when collected at 2.0 L/minute for a 1-hour period. NIOSH (method 6013) describes the measurement of hydrogen sulfide in the air by ion chromatography. This method has a working range of 0.6–14 ppm for a 20-L air sample and an estimated limit of detection of 11 μg per sample. However, sulfur dioxide may interfere with the measurement of hydrogen sulfide. The iodometric method has been utilized in analyzing hydrogen sulfide in the air. The method is based on the oxidation of hydrogen sulfide by absorption of the gas sample in an impinger containing a standardized solution of iodine and potassium iodide. This solution will also oxidize sulfur dioxide. The iodometric method is suitable for occupational settings. The accuracy of the method is approximately 0.50 ppm hydrogen sulfide for a 30-L air sample. Another application of the iodometric method is for the determination of hydrogen sulfide in fuel gas emissions in petroleum refineries. In this method, the sample is extracted from a source and passed through a series of impingers containing cadmium sulfate. The hydrogen sulfide is absorbed, forming cadmium sulfide, which is then measured iodometrically. The sensitivity range of this method is 8–740 mg/m3 (6– 520 ppm). Paper tapes impregnated with lead acetate have been widely used for air sample measurements of hydrogen sulfide in the field. The presence of other substances capable of oxidizing lead sulfide can lead to errors. This method has been improved by impregnating the paper with mercuric chloride or silver nitrate. Mercuric chloride paper tape is sensitive and reliable for measurement of hydrogen sulfide in air with a sensitivity of 0.7 μg/L. Tapes impregnated with silver nitrate are suitable for determination of hydrogen sulfide concentrations in the range of 0.001–50 ppm. Potentiometric titration with a sulfide ion-selective electrode as an indicator has been used to measure hydrogen sulfide in the air at ppb levels. The method has been shown to have very good accuracy and precision. No interference could be found from nitrogen dioxide, sulfur dioxide, or ozone. Passive card monitors can be used to detect hydrogen sulfide in workplace environments. These monitors can be categorized as quantitative, semiquantitative, and indicator cards. Quantitative cards use an optical reader to assess exposure and calculate a hydrogen sulfide concentration in air; the results are digitally displayed. Semiquantitative cards are read by comparing the exposed card to a chart or by observing a progressive color development in windows on the card that represent differing exposure concentration ranges. The indicator cards change color above a certain threshold concentration of hydrogen sulfide. Badges that can be worn in a worker’s, breathing zone that change color based on exposure to toxic gases, including hydrogen sulfide, are available from American Gas & Chemical Co. The sensitivity for the hydrogen sulfide badges is 10 ppm/10 minutes with a color change from white to brown . Other colorimetric methods for monitoring of hydrogen sulfide include handheld colorimetric tubes. Air is drawn through the tube and a color change indicates the presence of hydrogen sulfide by reaction with a chemical reagent in the glass tube. Tubes for hydrogen sulfide are available from Draeger Safety, Inc. in various measuring ranges from 0–5 ppm to 100– 2,000 ppm. Electrochemical sensors are the most commonly used sensors for toxic gases, including hydrogen sulfide, and are the best sensor for ambient toxic gas monitoring. These sensors are specific to a particular gas, are very accurate, do not get poisoned, and monitor at the ppm level. However, they have a narrow temperature range and a short shelf life, particularly in very hot and dry areas. When sensitivity to low concentrations of hydrogen sulfide (ppm levels) is needed, semiconductor sensors are one of the best sensors. Some advantages of semiconductor sensors for hydrogen sulfide include small size, ruggedness, and sensitivity to ppm concentrations. Disadvantages include slow response on aged sensors, requirement of a temperature controlled heater, and cost. The Iowa Department of Natural Resources (DNR) monitors airborne levels of ammonia, hydrogen sulfide, and odor concentrations new animal feeding operations. Approved monitoring methods and equipments for the hydrogen sulfide must incorporate a thermal oxidizer and an EPA reference method analyzer that is designed for sulfur dioxide. There are several instruments that meet the requirements for the Iowa DNR, all of which detect hydrogen sulfide by first oxidizing it to sulfur dioxide, which is then measured using a fluorescence detector. The hydrogen sulfide and total reduces sulfide analyzer (Model 101A) from Advanced Pollution Instrumentation, Inc. has a range of 0–50 ppb to 0–2 ppm for hydrogen sulfide. In addition, three hydrogen sulfide analyzers from Thermo Electron Corporation are also approved by the Iowa DNR. Minimum detection limits as low as 0.5 ppb can be achieved for models 45C and 450C, and 0.06 ppb with model 450C-TL, respectively. The APHA (1998) defines three categories of sulfides that must be taken into account for analytical methods measuring sulfides in water: total sulfide, dissolved sulfide, and un-ionized hydrogen sulfide. Total sulfide includes all sulfide containing species, dissolved hydrogen sulfide, bisulfide ion, and acid-soluble metal sulfides in suspended matter. Dissolved sulfide includes sulfide-containing components that remain after suspended solids have been removed. The concentration of the un-ionized hydrogen sulfide can be calculated from the concentration of dissolved sulfide components, pH of the solution, and the acidity constants for hydrogen sulfide using the equilibrium expressions for the ionization of hydrogen sulfide and bisulfide ion. Samples that contain sulfide species can be either analyzed immediately after collection, or preserved with a zinc acetate solution for later analysis. The addition of zinc ion (Zn2+) to the sample will precipitate any sulfides as zinc sulfide. A qualitative sulfide test, such as a precipitation test using potassium antimony tartrate or testing for hydrogen sulfide vapors using lead acetate paper or silver foil, can be useful and are advisable when testing industrial wastes that may contain substances that interfere with certain test methods, such as the methylene blue method. The total sulfide concentration in a water sample can be determined using an iodometric titration. In this method sulfide is reacted with a measured excess of iodine in an acidic solution; the remaining unreacted iodine is then determined by titration with a thiosulfate solution. This method is an accurate method for determining sulfide concentrations of >1 mg/L, if interferences are absent and the loss of hydrogen sulfide from the solution is avoided. The iodometric method is best suited for the analysis of samples freshly taken (i.e., from wells and springs). The methylene blue method is applicable to sulfide concentrations ranging from 0.1 to 20.0 mg/L. In this method, an amine-sulfuric acid reagent and a ferric chloride solution are added to the sample to produce methylene blue, which is then quantified colorimetrically. In the automated methylene blue method, a gas dialysis technique separates the sulfide from the sample matrix, which removes most inferences (i.e., turbidity and color). Addition of ascorbic acid, an antioxidant, improves sulfide recovery. The automated methylene blue method is applicable at sulfide concentrations from 0.002 to 0.100 mg/L. Potentiometric methods using a silver electrode are also suitable for determination of sulfide concentrations in water and are unaffected by sample color or turbidly. In this method, an alkaline antioxidant reagent (AAR) and zinc acetate are added to the sample. The potential of the sample is measured using an ion selective electrode (ISE) and the measurement is compared to a calibration curve. This method is applicable for sulfide concentrations >0.03 mg/L. Three methods for quantifying acid volatile sulfides in sediment have been used. These include methylene blue/colorimetric methods, gravimetry, and potentiometry with ion-selective electrode. Prior to measurement, the acid volatile sulfide in the sample is converted to hydrogen sulfide by acidification. The hydrogen sulfide is then purged from the sample and trapped in aqueous solution for the colorimetric and potentiometric methods. In the gravimetric method, hydrogen sulfide is trapped with silver nitrate (AgNO3), and the mass of the insoluble silver sulfide (Ag2S) that is formed is determined. The methylene blue/colorimetric method is generally preferred and is capable of determining acid volatile sulfide concentrations in sediment as low as 0.01 μmol/g (0.3 μg/g) dry weight. The gravimetric method can be used for samples with moderate or high acid volatile sulfides. However, below concentrations of acid volatile sulfides in dry sediment of 10 μmol/g (320 μg/g), accuracy may be affected by incomplete recovery of precipitate or by weighing errors. The limit of detection of the ion-selective electrode method as applied to measuring hydrogen disulfide in sediment was not reported. GC/FPD has been used to measure hydrogen sulfide, free (uncomplexed) sulfide, and dissolved metal sulfide complexes in water (Radford-Knoery and Cutter 1993). Hydrogen sulfide was measured in the headspace of the sample (100 mL) with a detection limit of 0.6 pmol/L (20 pg/L). A detection limit of 0.2 pmol/L (6 pg/L) was obtained for total dissolved sulfide. This method allows for the determination of the concentration of free sulfide that is in equilibrium with hydrogen sulfide. Complexed sulfide can be estimated from the difference between total dissolved sulfide and free sulfide. A molecular absorption spectrophotometry method, using a sharp-line irradiation source, has been developed for the determination of sulfide (as hydrogen sulfide) in water and sludge samples. The method was tested with measurements of real waste water samples. The limit of detection was 0.25 μg (1–10 mL sample volume).Following
- Xiaolan Huang (黄 晓澜) added an answer:Have you tried to get the hydrogen from these aluminum residues?Since these aluminum residues still have considerable amounts of metallic aluminum, why not to use it to get hydrogen as an new resource of energy? The product of hydrolysis of aluminum is hydrogen and aluminum hydroxide, which should further increase the values of residue.Thanks for your response. Dr. Cao. This might be a interesting approach to get the catalysis, however, either the waste from the secondary aluminum production, e.g. salt cake or the primary aluminum production, red mud, are huge. What I am concerning is the metallic aluminum in the wastes, minely SAP. How to use them before the waste to landfill?Following
- D. Fruchart added an answer:Information on solid-state hydrogen reservoirs?I'm interested not only in the principle of the hydrogen storage device, but the conceptual methods of hydrogen accumulation and extraction.Look at the web site of McPhy Energy please;
- Pavel V. Komarov added an answer:gPROMS Fuel Cell or ANSYS - Fluent, PEMFC module?Does anybody know which software would be best to use for high-fidelity predictive modelling of PEM fuel cell, stack and system, gPROMS Fuel Cell or ANSYS - Fluent, PEMFC module?
I want to solve key design problems and optimise design & operation. I want to implement the system of fuel cells to operate in a passive house.Following
- Partha Sarathy added an answer:How to optimize hydrogen production in water electrolysis?For hydrogen fuel in motor or car engine.Optimize the current and electrode area which determines the amount of hydrogen producedFollowing
- Ulrich Mutze added an answer:How can one find the eigenvalues of the hydrogen hamiltonian with orbital quantum number?Solving the classical problem of hydrogen hamiltonian eigenvalues one obtain energies (in atomic units) E_n=-0.5, -0.125... etc
These energies depend only on principal quantum number. How one can obtain orbital splitting in the electromegnetic field by means of numerically searching for eigenvalues of the hamiltonian with matrix elements < n L | H | n1 L1 >?
When I use only < n 0 | H | n1 0 > elements of free hamiltonian, I obtain E_n=-0.5, -0.125... etc (as expected).
If I use the whole matrix < n L | H | n1 L1 >, how can I obtain the correct energy levels in the case of atomic hamiltonian and in the case of the atom in the electromagnetic field by means of hamiltonian diagonalization?You are welcomeFollowing
- Closed account added an answer:How can I make simple electrolytic cells?I am planning to make an electrolytic cell for hydrogen production using carbon electrodes. Could anybody suggest some good literature on the concept and how I can measure the hydrogen evolution ?you can have a good idea about the design of your experiment by reading about polymer electrolyte membranes Fuel Cell and electrolyzer and their components.Following
- Ulrich Eberle added an answer:Any thoughts on market prospect of fuel cell PHEVs?In the projection, fuel cell PHEVs are found to be competitive for both the near term and long term, but for different reasons. I welcome any discussions and criticism of this finding, as elaborated by the paragraph right before Section 3.4 in the paper.
"The remarkable synergy between FC and plug-in battery is mainly due to the shared powertrain option—FC PHEVs, which appear to be competitive across all scenarios, both in the short term and the long term, but for common and different reasons. Low energy cost is the common reason. FC PHEVs have lower energy costs than SI PHEVs by relying on a cheaper (partly due to subsidy) and more efficient fuel (hydrogen). Compared to FCVs, FC PHEVs also achieve lower energy costs by fueling some miles with slightly cheaper electricity. The other reason for FC PHEVs to be attractive in the short-term market is its less severe range barrier. FC PHEVs consume less hydrogen fuel and thus require less frequent refueling trips, which is an important advantage in the early market with low hydrogen availability. Over time, this advantage diminishes as the hydrogen infrastructure expands, but the long-term advantage emerges—a competitive vehicle price of FC PHEVs due to progress of both FC and plug-in battery. As illustrated by Figure 5, the price of FC PHEV10s in 2045 is even a little lower than that of a SI PHEV10s, if all technical targets are met on time. The competition among SI PHEVs, FCVs and FC PHEVs reflects tradeoff among vehicle price, energy cost, and refueling inconvenience. This topic is worthy of further investigation because the knowledge about how consumers value energy costs and fuel availability is still insufficient"Dear Zhenhong Lin,
Not directly related to your specific questions on Fuel Cell PHEVs ... but I think nevertheless interesting in the framework of the discussion: Please find below a recent review co-authored by myself on the state of the art of fuel cell electric vehicles and hydrogen infrastructure. A well-to-wheel discussion of the fuel path is included, as well as a brief comparison with extended-range and pure battery electric vehicles.
It would be great if you consider the piece helpful.
- A.I. Manilov added an answer:What is the best procedure to measure hydrogen in photocatalytic water splitting?may be if we can avoid GC.The most simple way to measure the H2 evolution is displacement of water in an inverted measuring cylinder. The cylinder should be filled with water and placed over the electrode for H2 generation. The produced gas will displace the water volume corresponding to its quantity.
Such way was also used in our articles devoted to hydrogen extraction.
However, this method can be used if hydrogen is the sole product of the reaction, or it could be separated.Following
- Yury Mikhailovich Baikov asked a question:What is your opinion on any opportunity to use rechargeable batteries (+)C|KOH.H2O (solid)||(TiFe or Sn)?Electrochemically active heterostructures "any electrodes - solid protonic conductors, based on solid eutectics or crystalline hydrates of KOH or NaOH" are studied in Ioffe Instutute (St-Petersburg) from fundamental view point on physico-chemical problems of proton-conducting materials at room-temperature range. We are srudying as electrodes IV group (C. Si, Ge, Sn) and factually novel solid protonic conductors KOH.nH2O (n=o,5; 1,0; 2,0). See http://www.solidionic.com and publication in researchgateFollowing
- Yannick Perez added an answer:Solar-hydro-wind combination?I am trying to find a good paper describing the combination of Hydro-wind -solar or anyone in this category of research, please feel free to get in touch for information sharing.You can find data about real generation produced in france for hydro-solar wing in RTE website for free.