The downfalls of conventional electrolysis - and how to fix them

[iquant]

Traded a few emails with Alaskastar regarding a Sodium Battery of sorts. 
Through our exchange he suggested taking a look at Ammonia for my particular application... 
Wow!  theoretically the electrolysis of ammonia consumes 95% lower energy than a water electrolyzer!

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Electrolysis of Ammonia: an in-Situ Hydrogen Production Process
Gerardine G. Botte, Luciano Benedetti, and Juan Gonzalez. Chemical Engineering, Ohio University, 183 Stocker Center, Ohio University, Athens, OH 45701

Introduction

Hydrogen is the main fuel source for power generation with fuel cells, but its storage and transportation are still major issues. To overcome these problems, hydrogen has been stored and transported via other chemical compounds, such as alcohols, hydrocarbons, ammonia, etc. In many ways, ammonia is an excellent hydrogen carrier [1]; liquid ammonia represents a convenient way of storing supplies of hydrogen, boasting a specific energy density (kWh/l) 50% higher than liquefied hydrogen. Ammonia is also easily condensed at ambient temperature (under 8 bar of pressure), which makes it a good choice for transportation and storage. Even though ammonia is flammable within defined limits (16%-25% by volume in the air) and toxic (above 25 ppm) its presence can be detected by its characteristic odor (above 5 ppm). Ammonia is produced world-wide in large quantities (more than 100 million ton/year), which allows the effect of economy of scale on the cost of production. Its decomposition by electro-oxidation in alkaline media at low overpotentials is NOx and COx free with nitrogen and water as products of reaction [2].

The Electrochemical Engineering Research Laboratory (EERL) at Ohio University (OU) is working on the development of a new technology for the production of hydrogen in-situ from the electrolysis of ammonia. The reactions take place in alkaline medium as shown [3-5]:

2NH3(aq) + 6OH- -> N2(g) + 6H2O + 6e- (1)

2H2O + 6e- -> 3H2(g) + 6OH- (2)

Reactions (1) and (2) take place at the anode and cathode, respectively. At 25 oC the ammonia oxidation potential is -0.77 V versus Standard Hydrogen Electrode (SHE), only 0.06 V less negative than the value of -0.83 V vs. SHE for hydrogen evolution in alkaline solution. Therefore, thermodynamic values are much in favor of the production of hydrogen coupled to the oxidation of ammonia compared to hydrogen production by electrolysis of water, for which the theoretical cell voltage is 1.23 V. One of the advantage of this process is its ease of integration with renewable energy (electricity) sources. Because the energy consumption is low, the cell could operate with renewable energy (or by stealing part of the energy of a PEM hydrogen fuel cell if the ammonia electrolytic cell operates close to the theoretical potential). Therefore, hydrogen could be produced on demand, minimizing the needs for hydrogen storage. The theoretical energy consumption during ammonia electrolysis can be calculated from the standard potential of the cell and is equal to 1.55 Wh/g H2 while the electrolysis of water requires at least 33 Wh/g H2 at standard conditions, this means that theoretically the electrolysis of ammonia consumes 95% lower energy than a water electrolyzer. The scalability of the technology as well as its ability to easily operate in an on-demand mode facilitates the technology's ability to interface with renewable energy sources including those whose production of electricity may vary with time (for example, wind and solar energy).

Recently, we had developed novel catalysts that enhance the oxidation of ammonia in alkaline medium. The catalysts are made by electrodeposition of nobel metals on carbon fibers [5]. The novel electrocatalysts allow the achievement of current densities of up to 75 mA/cm2 at cell voltage of 0.45 V. Within this context, the objective of this paper is to evaluate the technical and economical feasibility of producing hydrogen from the electrolysis of ammonia for distributed power generation using the novel electrodes. These results will be presented at the meeting.
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Ohio University Licenses Ammonia Electrolyzer Technology to American Hydrogen
6 August 2007

Ohio University has granted a worldwide exclusive license to American Hydrogen Corporation, a subsidiary of American Security Resources Corp., to commercialize the patent-pending catalytic electrolyzer technology developed by Ohio University’s Dr. Gerardine Botte, associate professor of Chemical and Bio-Molecular Engineering at the Russ College of Engineering and Technology.

Ammonia electrolysis could produce hydrogen at a current cost of $0.899/kg H2, according to Botte. The US Department of Energy’s target cost for hydrogen is $2/kg H2. The ammonia process is also much less energy intensive than water electrolysis, requiring 1.55 W-h/g H2, compared to 33 W-h/gH2 for water electrolysis.

Ammonia electrolysis could be extended to use ammonia from waste water (e.g., from livestock or municipal waste water) as a feedstock as well.

Ammonia electrolysis couples the ammonia electro-oxidation reaction with the hydrogen evolution reaction for the production of high-purity hydrogen in an alkaline electrolytic cell. The reactions are as follows:

    2NH3(aq) + 6OH- â†' N2(g) + 6H2O + 6e- (1)

    6H2O + 6e- â†' 3H2(g) + 6OH- (2)

The overall reaction is:

    2NH3(aq) â†' N2(g) + 3H2(g) (3)

One of the challenges faced by ammonia electrolysis is the need for the development of improved catalysts for ammonia electro-oxidation. While significant current densities can be obtained from platinized Pt electrodes, higher current densities quickly deactivate the catalyst.

A number of studies have tried different combinations of catalyst materials, with unsatisfactory resultsâ€"very low current densities and the deactivation of the catalyst.

Botte and her team combined a catalystâ€"containing Raney nickel, platinum, and rhodium prepared by electrodepositionâ€"with an operating procedure for the electrolytic cell that prevents deactivation of the catalyst over a long period of time.

[ramset]

Wow,
This is quite interesting info !!

Thanks iquant!
Thanks Chris hunter!

And of course Dutchy!

Fellahs this is amazing stuff!
Dutchy you had some ideas?

Chet

[Stressed101]

Ok, still following with great interest, but not up on all the physics of it.   I know that ammonia mixed with other compounds can release deadly gasses....are you considering inducing a magnetic field through a vessel containing super-saturated NAOH with ammonia vs with water?  Is this safe?

[iquant]

Here is the deal..

1 liter of liquid Ammonia stores 2x the amount of hydrogen as 1 liter of liquid hydrogen!
Liquid Ammonia can be stored at ambient temp & pressure and theoretically requires 1/20 the equivalent H20 energy for electrolysis.

Storing Liquid Hydrogen requires Cryogenic dewars... 
Storing Gaseous Hydrogen requires High Pressure composite tanks.

1 Liter of Liquid Hydrogen expands to 851 Liters of Hydrogen gas at 1 ATM 20C.
1 Liter of Liquid Ammonia through electrolysis liberates 1702 Liters of Hydrogen Gas

A 34 Liter 700 bar High Pressure Hydrogen tank stores 28 liters of liquid hydrogen expanding to 24,000 liters of gas.
Lots of safety issues to contend with not to mention the cost of the equipment.

14 Liters of Liquid Ammonia contains 24,000 liters of hydrogen gas...  full capacity of the high pressure tank and can be generated on demand consuming less energy than produced.
 
A US 18 Gallon tank of Ammonia with on board electrolysis (1/20th the energy requirement) would give a hydrogen vehicle 5x the range of an existing hydrogen tank + air conditioning (Ammonia is a refrigerant).  All the infrastructure is already in place and Ammonia is relatively dirt cheap..  $400 a ton..  $1 per gallon

Horizon Fuel Cell technologies has a 5kW PEM Fuel Cell consuming 70l / minute.  About 15 gallons of Ammonia would provide 5kw of power for 24 hours.  The average US Household consumes 920 Kwh / month = approx 120 Gallons of Ammonia.

Ammonia is probably the best Hydrogen Battery...


"On-board hydrogen storage and production via ammonia electrolysis was evaluated to determine whether the process was feasible using galvanostatic studies between an ammonia electrolytic cell (AEC) and a breathable proton exchange membrane fuel cell (PEMFC). Hydrogen-dense liquid ammonia stored at ambient temperature and pressure is an excellent source for hydrogen storage. This hydrogen is released from ammonia through electrolysis, which theoretically consumes 95% less energy than water electrolysis; 1.55 Wh gâˆ'1 H2 is required for ammonia electrolysis and 33 Wh gâˆ'1 H2  for water electrolysis. An ammonia electrolytic cell (AEC), comprised of carbon fiber paper (CFP) electrodes supported by Ti foil and deposited with Ptâ€"Ir, was designed and constructed for electrolyzing an alkaline ammonia solution. Hydrogen from the cathode compartment of the AEC was fed to a polymer exchange membrane fuel cell (PEMFC). In terms of electric energy, input to the AEC was less than the output from the PEMFC yielding net electrical energies as high as 9.7 ± 1.1 Wh gâˆ'1 H2 while maintaining H2 production equivalent to consumption"

Edit Here is a link for a video showing the reaction of Sodium Metal and Liquid Ammonia.

Ok, still following with great interest, but not up on all the physics of it.   I know that ammonia mixed with other compounds can release deadly gasses....are you considering inducing a magnetic field through a vessel containing super-saturated NAOH with ammonia vs with water?  Is this safe?

[ZathEros]

Gentlemen,
So far I have found three things that don't work.
I was able to conduct a few experiments using High frequency RF and UHF RF energy to split water. So far I have not had any luck.
I took a 250 ML graduated cylinder and wrapped  24 ga. wire around the cylinder fro the base to about 6" above the base.
I attached a 50 300 watt carbon pile resistor to one end of the wire and chassis ground. The other end of the wire was attached to the center conductor of a pl-259 RF chassis connector.
I chose this method for two reasons-
1) To not destroy my radio gear in the pursuit of the experimentation.
2) This method will definitely deliver RF power ( field ) to the cylinder.

I filled the cylinder with a saturated aqueous solution of sodium Hydroxide. I powered the coil on the cylinder with ~40 watts @ 146 Mhz and observed the cylinder to look for any hint of gas production in the cylinder.
Nothing.
I then tried a lower frequency. I tried 28 Mhz @ ~ 60 watts.
Nothing.
I went down to 18 Mhz @ ~ 40 watts.
Again nothing.

I will repeat these same experiments with saltwater when I get time.
Zatheros