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New Approach to Release Hydrogen from Ammonia Borane Promising for Fuel Cell Vehicle Applications

Hydrogen yield from the hydrothermolysis approach as a function of AB concentration, at different operating conditions. Source: Diwan et al. Click to enlarge.

A team of chemical engineers at Purdue University have developed a noncatalytic hydrothermolysis approach to release hydrogen from ammonia borane (AB)—a promising hydrogen storage material containing 19.6 wt% hydrogen—in yields and under conditions promising for application in on-board hydrogen storage systems for fuel cell vehicles.

In a paper published online recently in AIChE Journal, the researchers report that the maximum hydrogen storage capacity from a 77 wt% solution of AB at 85 °C (185 °F)—i.e., near PEM fuel cell operating temperatures—was 11.6 and 14.3 wt% at 14.7 and 200 psia pressure, respectively. Research findings were also presented 15 June during the International Symposium on Chemical Reaction Engineering in Philadelphia.

To our knowledge, on a material basis, the AB hydrothermolysis process is the first one to provide such high hydrogen yield values at near PEM fuel cell operating temperatures without use of catalyst. Further, for the same temperature range, these yield values are higher than previously reported in the literature by either AB hydrolysis or thermolysis alone. It is worth noting that DOE system targets for H2 yield are 4.5 and 5.5 wt% for the years 2010 and 2015, respectively. The material-based H2 yield (~14.3 wt%) achieved in this work is sufficiently higher than the target values, suggesting that the noncatalytic AB hydrothermolysis method is promising for hydrogen storage in fuel cell based vehicle applications.

—Diwan et al.

The paper was written by former Purdue doctoral student Moiz Diwan, now a senior research engineer at Abbott Laboratories in Chicago; Purdue postdoctoral researcher Hyun Tae Hwang; doctoral student Ahmad Al-Kukhun; and Arvind Varma, R. Games Slayter Distinguished Professor of Chemical Engineering and head of the School of Chemical Engineering. Purdue has filed a patent application on the technology.

There are two conventional approaches to releasing hydrogen from AB: thermolysis and catalytic hydrolysis. Due to limited AB solubility in water, catalytic hydrolysis provides low theoretical hydrogen yield (~5.6 wt%) and also requires expensive catalysts such as ruthenium, the authors note. Thermolysis, on the other hand, requires heating the material to more than 170 °C (338 °F) to release sufficient quantities of hydrogen. However, fuel cells that will be used in cars operate at about 85 °C.

The new process also promises to harness waste heat from fuel cells to operate the hydrogen generation reactor, Varma said.

In the AIChE paper, the researchers investigated their thermolysis approach over a wide range of AB concentrations, pressure, and temperature. In the experiments, they used deuterium (D2O) instead of H2O to clarify the reaction mechanism, enabling them to trace how much hydrogen is generated from the hydrolysis reaction and how much from the thermolysis reaction, details critical to understanding the process.

It was shown that with increasing AB concentration up to 77 wt%, the H2 molar equivalent increased, while the HD molar equivalent decreased. Thus the role of thermolysis (H2 yield), as compared to hydrolysis (HD yield), increases with AB concentration. The effect of pressure on hydrogen yield was found to be insignificant up to 60 wt% AB. An important finding is that for AB concentration > 43 wt %, Treactor ~85 °C is sufficient to release the same amount of hydrogen as at Treactor ~135 °C. This, however, does not hold for lower AB concentrations (≤ 32 wt%).

The maximum observed hydrogen storage capacity, obtained at 77 wt% AB concentration and Treactor ~85 °C, was 11.6 and 14.3 wt% at pressure 14.7 and 200 psia, respectively. Transient experiments showed that during the hydrothermolysis process, the sample temperature increased sharply due to heat evolution by reaction (both AB hydrolysis and the first step of AB thermolysis are exothermic). The H2 and HD evolution began simultaneously at Tsample ~105 °C, and reached maximum value within a few seconds, which suggests rapid reaction kinetics.

—Diwan et al.

Future work on hydrothermolysis will explore scaling up the reactor to the size required for a vehicle to drive 350 miles before refueling. Additional research also is needed to develop recycling technologies for turning waste residues produced in the process back into ammonia borane.

The technology may also be used to produce hydrogen for fuel cells to recharge batteries in portable electronics, such as notebook computers, cell phones, personal digital assistants, digital cameras, handheld medical diagnostic devices and defibrillators.

The recycling isn’t important for small-scale applications, such as portable electronics, but is needed before the process becomes practical for cars.

—Dr. Varma

The research has been funded by the US Department of Energy by a grant through the Energy Center in Purdue’s Discovery Park.


  • Moiz Diwan, Hyun Tae Hwang, Ahmad Al-Kukhun, and Arvind Varma (2010) Hydrogen Generation from Noncatalytic Hydrothermolysis of Ammonia Borane for Vehicle Applications. AIChE Journal doi: 10.1002/aic.12240



When used in electrified FC vehicles it would be very similar the battery swapping EVs except that the very costly FC will always be an extra cost. However, the extra driving range could be interesting for certain customers, like long range buses, trucks, locomotives etc. Pure EVs (with batteries) are better for short driving range vehicles. PHEVs could be a lower cost solution for long driving range vehicles.


It seems they are nowhere near 'recycling'.
I don't get the big advantage over methane.
the reaction is NH3BH3 --> NHBH + 2H2
Then you have a lot of NHBH that needs to be returned to a recycling plant...

If you use a reformer using methane and water, you have
CH4 + 2H2O --> CO2 + 3 H2.
You can let the CO2 fly and recycle it wherever on the planet you have cheap H2.
(or you can do it with CH3OH, which is an easy liquid)
It seems to me this will be much easier, and faster to realise than this exotic amonium borane, which is probably much more toxic than CH4 or CH3OH)

Ole Grampa

@ Harvey D., the expensive component in fuels is the platinum or other catalyst substance. Inexpensive, effective substitutes have already been found.
Hydrogen power will be practical- soon- no matter how hard you try to convince the world otherwise.


@ John Thompson,

Few people on this list are rooting for any particular technology to fail to live up to expectations. Most of us have been frustrated at how many next-big-thing announcements were fundamentally impractical because of high up front costs, bad EROIE, requirements for massive new infrastructure, toxic byproducts, or higher costs per KwHr or per mile than fossile fuels.

H2 Fuel Cells are clean if they burn straight H2, but pure H2 is a lousy (read inefficient) way to store energy. Electricity produced in gas turbine cogeneration plants or better yet, renewable sources, and fed to BEV/PHEV is a much more practical and efficient approach than fuel cells.


Actualy I would expect this would more likely be used to transport h2 to the gas station and back as they would be able to transport several tons of h2 at a time without the need of special tankers.

Mercy Vetsel

So a gallon of gasoline weights about 2.8kg. At 14.3% yield, 2.8kg of AB would yield 0.4kg of H2, equal to about .4 gallons of gasoline in energy content.

However, due the the 2.5 times greater efficiency of a FCV, 14.3% yields of H2 would mean that pound for pound, an AB H2 FCV would go 20% farther than a gas vehicle on the same mass and volume (AB is slightly denser than gasoline) of fuel.



Water weighs about 4 kg per gallon and im fairly sure gasoline is very close to water in weight.

Mercy Vetsel

> im fairly sure gasoline is very close to water
> in weight.

Well, it's within a kg per gallon. Water is 3.8kg/gallon, gasoline is 2.8kg/gallon.


I should add that a gallon of methanol stores 0.34kg of hydrogen without considering losses due to the reformation process.

Of course the biggest obstacle blocking H2 FCV's is the cost and durability of the fuel cells.



Actualy gm went from 30000 mile lifespan on thier fuel cells to 80000 and the new gen they are building starts at 120000 miles.. and thats to 80% power so its actualhy not much faster degrading then an ice engine and likely will be more durable then them before 2015.

As for costs... you have to remember up until recently fuel cells were only made for research and a few very special needs. They werent exactly designed to be cheap to make or easy to make but the newer designs now have been made for just that purpose and are massively easier and faster to produce and as a result cheaper.

Henry Gibson

Diesel engines can be made nearly as efficient as fuel cells, and can burn dimethyl-ether made from coal and stored in tanks similar to propane tanks. There are ways to burn hydrocabon fuels clean enough to breath the exhaust.

The operation of an automobile is the inefficient part, and this inefficiency is reduced by the use of series hybrid vehicles such as diesel electric locomotives. A single piston diesel engine is good enough for plug in hybid electric vehicles. The newest version of the OPOC engine can have a Still cycle added to it for more efficiency, but why go to the expense if going 65 insteady of 75 will save lots of fuel.

Electric cars with the new DURATHON (GE ZEBRA) battery are far more than adequate for most atuomobile trips. Fuel burning range extenders can be used for the rare long trip. ..HG..

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