Nanotechnology artificial leaves for hydrogen production

[OKIsItJustMe]

http://www.nanowerk.com/spotlight/spotid=15381.php

Posted: March 18, 2010

Nanotechnology artificial leaves for hydrogen production

(Nanowerk Spotlight) Artificial photosynthesis, using solar energy to split water generating hydrogen and oxygen, can offer a clean and portable source of energy supply as durable as the sunlight. Natural photosynthesis uses chlorophyll to absorb visible light and many solar hydrogen cells are imitating this process by using light-sensitive organic dye molecules as light absorbers and then transfer the absorbed energy to a catalyst that reduces protons to hydrogen (read: http://www.nanowerk.com/spotlight/spotid=14845.php">"Another step towards inexpensive hydrogen production from sunlight").

Today, over 130 materials and derivatives are known to facilitate photocatalytic splitting of water to produce hydrogen. Many efforts have been made to design new photocatalysts of different materials such as transition-metal oxides or metal oxynitrides or in nanotechnology research to design photocatalysts with various nanoscale morphologies such as nanoparticles, nanosheets, nanowires, etc for enhanced light-harvesting and catalytic efficiency.

"Using sunlight to split water molecules and form hydrogen fuel is one of the most promising tactics for kicking our carbon habit," Di Zhang tells Nanowerk. "Of the possible methods, nature provides the blueprint for converting solar energy in the form of chemical fuels. A natural leaf is a synergy of the elaborated structures and functional components to produce a highly complex machinery for photosynthesis in which light harvesting, photoinduced charge separation, and catalysis modules combined to capture solar energy and split water into oxygen and hydrogen efficiently."

Zhang, a professor at Shanghai Jiao-Tong University in China and director of the university's State Key Laboratory of Metal Matrix Composites, points out that the design of efficient, cost-effective artificial systems by coupling of leaf-like hierarchical structures and analogous functional modules under the guidance of the key steps of natural photosynthesis into hydrogen would be a major advance in energy conversion.

...

(Follow the link for more...)

[happyslug]

1. Two problems with this

1, Yes, their are various ways to split the Oxygen atom from Hydrogen Atoms that make up water, but all are high in energy costs. Furthermore remember it takes as much energy to spit the atoms apart (by this I mean splitting the Oxygen atom from the Hydrogen atoms) as you get when you "burn" the Hydrogen in your car (And re-unite the Hydrogen atoms to the Oxygen atom). There is no free lunch. Please note the above assume no "Loss" and you will have some sort of "loss" in both re-actions.

2. Hydrogen is the smallest atom know to man. In the gaseous state can be contained for the Gaseous state of any atom is larger then when it is in the Liquid or solid form, thus we have material that can contain Hydrogen gas with a good bit of efficiency. On the other hand, when you compress Hydrogen (Which requires additional energy) to a liquid form (So you can have Hydrogen in your "Gas Tank") the resulting container will leak Hydrogen at about 1% per day. This leak is right through the container wall itself, not the seals as with gasoline but right through the container walls. It is for this reason Hydrogen is produced and sold locally, after about three months is is almost all gone (Yes I know as Hydrogen leaks you have less to leak out so the am out of Hydrogen lost drops over time, but the rate of drop is constant thus I am using 90-100 days to say all the Hydrogen will be gone. Much of the hydrogen will still be in the Container but no where near what it was 100 days before).

While most people do NOT keep fuel in their car for more then two weeks at a time, your local gasoline station does. Expect a huge loss of Hydrogen after it is produced. This loss, like losses as part of transferring from the storage tank to your car, will have to be added to the cost of the Hydrogen you end up paying for.

3. Do to the fact Hydrogen is a Gas at normal Temperatures and pressure, (Hydrogen only becomes liquid at 20.28 K, -252.87 °C, -423.17 °F at normal pressure), to be store-able Hydrogen must be pressurized till its Temperature and pressure is below its "boiling point". This requires a very strong and heavy container (and its weight has only a minimal affect on Hydrogen leaking through the container walls) which requires careful handling AND additional energy to be moved around as part of your car.

More on Hydrogen itself:
http://en.wikipedia.org/wiki/Hydrogen

Repeating an old Joke (Modified to apply to Hydrogen) "Hydrogen is the energy of tomorrow and always will be". Hydrogen has a lot of things going for it. Can be produced out of water, can be produced almost anywhere. Has the most energy for any chemical source of energy (Nuclear provides more power per pound but that is do to Nuclear frisson or fusion of atoms themselves NOT the energy connecting atoms to other atoms). The problems are first there are NO nature source of Hydrogen, it has to be made (Can be made anywhere BUT takes energy to be made), Second the high loss rare do to the fact it is impossible to store quantities of Hydrogen in any form other then the Liquid state AND then even in the liquid state almost impossible to keep in storage for any length of time. These are problems inherent with the use of Hydrogen and no one has addressed them for under present scientific theory there is no solution. Now if a cheap way is found to convert water to Hydrogen and so so when the Hydrogen is wanted then most of these problem can be avoided but that means a access to some sort of power at every filling station that would equal the power from you local power station (i.e. your local power station where your gasoline station is today). Possible? Yes, probable NO. That is why people like me foresee a fundamental change in out social structure, a move back to the inner cities do to abandonment of the Automobile as opposed to the various attempts to preserve the automotive culture we Americans have adopted since the 1920s.

[OKIsItJustMe]

2. Have you been keeping up on the research?

1) Yes, their are various ways to split the Oxygen atom from Hydrogen Atoms that make up water, but all are high in energy costs. ...

Daniel Nocera (and company) at MIT have a catalyst which seems to be close to 100% efficient, splitting water using electricity.
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=234520&mesg_id=234557

Scientists from East Anglia have a catalyst which seems to be 60+% efficient at splitting water using sunlight.
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=234625&mesg_id=234625

Those aren't "high in energy costs" in my opinion.


2. Hydrogen is the smallest atom know to man. ...

(So, it's difficult to contain.)

Scientists at NIST have just reported on their research in using layered graphene to contain hydrogen.
http://www.democraticunderground.com/discuss/duboard.php?az=show_mesg&forum=115&topic_id=236869&mesg_id=236869


3. Do to the fact Hydrogen is a Gas at normal Temperatures and pressure, (Hydrogen only becomes liquid at 20.28 K, -252.87 °C, -423.17 °F at normal pressure), to be store-able Hydrogen must be pressurized till its Temperature and pressure is below its "boiling point". ...

The NIST research says, "The GOFs can retain 1 percent of their weight in hydrogen at a temperature of 77 degrees Kelvin and ordinary atmospheric pressure" (i.e. both warmer, and at much less pressure.)

[wtmusic]

3. According to this source, Nocera's formulation is "highly toxic"

http://www.ci.tucson.az.us/arthazards/paint1.html

Is "close to 100%" the opposite of "partial zero"?

http://en.wikipedia.org/wiki/Partial_zero-emissions_vehicle

[OKIsItJustMe]

5. Says the man who wants to power individual cars with Polonium!

:rofl:

http://web.mit.edu/newsoffice/2008/oxygen-0731.html

...

Requiring nothing but abundant, non-toxic natural materials, this discovery could unlock the most potent, carbon-free energy source of all: the sun. "This is the nirvana of what we've been talking about for years," said http://web.mit.edu/newsoffice/2008/chesonis-0422.html">MIT's Daniel Nocera, the Henry Dreyfus Professor of Energy at MIT and senior author of a paper describing the work in the July 31 issue of Science. "Solar power has always been a limited, far-off solution. Now we can seriously think about solar power as unlimited and soon."

...

[happyslug]

6. First, when I mention "High in energy costs" i meant in relation to Energy "saved"

Hydrogen is an energy storage device given it does NOT exist in nature on its own. As such, compared to gasoline for example, hydrogen has more energy, but to make it into a usable product takes more energy then we put into it. Unlike Gasoline which is derived from oil which developed over millions of years (From plants that existed millions of years ago) the cost to convert oil to fuel is low in energy costs i.e. you put less energy in drilling, pumping, shipping and refining oil into gasoline then you get out of it. Even Shale oil (at the present time, this is expected to change) has a 2-1 energy surplus (i.e. for every one gallon of gasoline you put into shale oil you get two gallons a net increase in energy). You can NOT have that in Hydrogen, Hydrogen is a net energy SINK i.e. to get an equivalent gallon of gasoline power you have to put MORE ENERGY INTO PRODUCING THE ENERGY then you get out of it so in effect you have LESS THEN A GALLON OF ENERGY when you are finished. No matter what technology you use you can NOT get over that hurtle. Please note I am assuming 100% efficiency, the lost is inherent in transferring one form of energy to another, thus the 60% efficiency finding is meaningless, in fact it means you will need almost the equivalent energy of 1 1/2 gallons to produce the energy of 1 gallon of gasoline. That is the hurtle that hydrogen has to get over and can not. The energy one get from burning Hydrogen will always be less the the energy to produced that hydrogen.

As to the GOF site you cite, you forgot to mention the most important paragraph:

The GOFs can retain 1 percent of their weight in hydrogen at a temperature of 77 degrees Kelvin and ordinary atmospheric pressure—roughly comparable to the 1.2 percent that some well-studied metal-organic frameworks can hold...

When I cited 1 % loss I was assuming a METAL-ORGANIC system, which still has a 1.2% leakage that this GOF matches. 1% leakage is still to high for any long term (more then one month) storage.

Thus even with these two sets of facts, you still have to have some sort of external energy to make the Hydrogen when it is needed. Storage is NOT a good solution do to the leakage thus hydrogen must be produced on site. I like the research and I hope it continues but again it tend to show the old saying on Hydrogen,"It is the fuel of tomorrow and always will be".

[OKIsItJustMe]

8. Except, hydrogen is not the fuel of tomorrow

NASA's been using it for more than a half century now.

http://www.nasa.gov/topics/technology/hydrogen/hydrogen_fuel_of_choice.html

Liquid Hydrogen--the Fuel of Choice for Space Exploration

Despite criticism and early technical failures, the taming of liquid hydrogen proved to be one of NASA's most significant technical accomplishments. . . . Hydrogen -- a light and extremely powerful rocket propellant -- has the lowest molecular weight of any known substance and burns with extreme intensity (5,500°F). In combination with an oxidizer such as liquid oxygen, liquid hydrogen yields the highest specific impulse, or efficiency in relation to the amount of propellant consumed, of any known rocket propellant.

Because liquid oxygen and liquid hydrogen are both cryogenic -- gases that can be liquefied only at extremely low temperatures -- they pose enormous technical challenges. Liquid hydrogen must be stored at minus 423°F and handled with extreme care. To keep it from evaporating or boiling off, rockets fuelled with liquid hydrogen must be carefully insulated from all sources of heat, such as rocket engine exhaust and air friction during flight through the atmosphere. Once the vehicle reaches space, it must be protected from the radiant heat of the Sun. When liquid hydrogen absorbs heat, it expands rapidly; thus, venting is necessary to prevent the tank from exploding. Metals exposed to the extreme cold of liquid hydrogen become brittle. Moreover, liquid hydrogen can leak through minute pores in welded seams. Solving all these problems required an enormous amount of technical expertise in rocket and aircraft fuels cultivated over a decade by researchers at the National Advisory Committee for Aeronautics (NACA) Lewis Flight Propulsion Laboratory in Cleveland.

Today, liquid hydrogen is the signature fuel of the American space program and is used by other countries in the business of launching satellites. In addition to the Atlas, Boeing's Delta III and Delta IV now have liquid-oxygen/liquid-hydrogen upper stages. This propellant combination is also burned in the main engine of the Space Shuttle. One of the significant challenges for the European Space Agency was to develop a liquid-hydrogen stage for the Ariane rocket in the 1970s. The Soviet Union did not even test a liquid-hydrogen upper stage until the mid-1980s. The Russians are now designing their Angara launch vehicle family with liquid-hydrogen upper stages. Lack of Soviet liquid-hydrogen technology proved a serious handicap in the race of the two superpowers to the Moon.4 Taming liquid hydrogen is one of the significant technical achievements of twentieth century American rocketry.

The above excerpt is from the Introduction to http://history.nasa.gov/SP-4230.pdf">Taming Liquid Hydrogen: the Centaur Upper Stage Rocket, 1958-2002 →. This report details why the Centaur was so important in NASA history as an upper stage rocket -- the critical link between its booster stage (Atlas or Titan) and the mission's payload (satellite or spacecraft).

[happyslug]

9. Hydrogen has always been used, the issue its it usability for day to day use

And such usage is just not viable under any foreseeable scenario. Remember I am NOT talking about Rockets to the moon, but to and from work.

[OKIsItJustMe]

10. Right

The objections you raise to it however I don't believe hold up well to critical scrutiny.

For example, you say it will leak right out through the walls of a storage tank at the rate of about 1% a day. With current technology, that's true. So, how is it that NASA is able to use hydrogen to fuel rockets? Well, for one thing, they don't leave them sitting fully fueled on the pad for months on end.

Now, I don't know about you, but I tend to fill my current car's fuel tank once every week or two. (Let's be generous, and say I do it once a month.) So, how much of my (theoretical) hydrogen will I lose in that month's time?

[Statistical]

12. About 7% with current technology.

That assumes that you use roughly 1/14th the tank capacity per day and losses are 1%.

7.09% would be the amount lost vs 92.93% consumed.

The reason it isn't 14% is because the amount in tank decreases it day as you consume some of the fuel.

[OKIsItJustMe]

13. Now, now, I wasn't calling on you

However, I'll give you credit.

[happyslug]

14. NASA has moved away from Hydrogen for that reason

When Hydrogen was used, for example the Saturn V Rockets of the Apollo program, there were kept being fueled till just minuted before launch. Thus the subsequent loss was acceptable. The super heavy Rockets used by the Air Force (The Atlas, the Titan II etc) of the 1960s were treated the same (And why most of them were replaced by solid fueled smaller Minuteman rockets in the 1970s). Even today when hydrogen is used, it is used as the base fuel, kept being filled till launch. When such constantly fueling is not possible, solid fuel rockets are used.

The Space Shuttle uses both Solid Fuel and Hydrogen fuel rocket engines. The solid fuel are the booster, the Hydrogen fuel is used in the Shuttle itself:

Space Shuttle Booster Rockets:
http://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#Propellant

Now the Shuttle itself hold no fuel. Its fuel is provided by the External tank, which fuel is used up by the Shuttle as it reaches space and then discarded (i.e. does not stay on shuttle for more then is needed to get to Orbit):
http://en.wikipedia.org/wiki/Space_Shuttle_external_tank

Yes the Shuttle is NOT flown to the ground, it is nothing but a glider as it goes from Orbit to ground. It has some fuel for use to maneuver in space but not enough to move it up in orbit (Yes, once in orbit the Shuttle MUST land or stay in its orbit, if it is desired to go to a higher orbit, the Shuttle must land and be re-launched).

As to your home gas tank, it is 1% per day. In week that will be less then 7% (But lets be honest each day you will have less fuel in the tank and thus lose less fuel at 1% per day rate, thus I believe it will be closer to 5% lost). On the other hand how much fuel will you use to haul around the extra weight required do to the much heaver and more solid fuel tank? In the 1970s and 1980s the big three all reduced the size of their cars gas tanks so to maximize mileage on the EPA mileage test. Why, gasoline has weight and that extra weight affected fuel economy. The same with the more solid fuel tank for Hydrogen, merely having the tank on your car may cost an extra 5% use of fuel. Thus we may be seeing 10% or more extra fuel between the loss of Hydrogen AND the cost of hauling the Hydrogen around.

[OKIsItJustMe]

16. SRB's have their own disadvantages

One of the biggest disadvantages with solid fuel rockets is that once started, they cannot be stopped (until they burn out.) So, a shuttle launch starts with the "main" (liquid fueled) "engines." Once they are successfully going, then the solid rocket boosters are set off, and the shuttle is committed.

Solid rockets are also used once (and only once) so, for example, they're useless for maneuvering thrusters.

As for the shuttle, if it didn't have (relatively small) fuel tanks on-board, their fuel cells wouldn't function, and (with no thrusters) they'd be reduced to trying to maneuver by waving their hands out of the windows.

[OKIsItJustMe]

17. How badly is the Honda FCX Clarity penalized for carrying around a hydrogen tank?

http://automobiles.honda.com/fcx-clarity/refueling.aspx

With a chart-topping EPA-certified 61 mpg equivalent (60-mile per Kg), the FCX Clarity FCEV is capable of traveling up to 240 miles before refueling.* Of course, your mileage and range will vary based on driver use and vehicle condition.

...

[Statistical]

18. Weight of hydrogen is less than equivelent weight of battery pack.

Hydrogen contains 143MJ of energy per kg. Now only physicists talk in terms of MegaJoules so lets covert it to something we know. 3.6MJ per kWh.

That is a staggering 40 kWh per kg.

Lets compare that to lithium-ion
Use Tesla Roadster as an example
http://en.wikipedia.org/wiki/Tesla_roadster

Battery pack is 53kWh and weighs 450kg.
Energy density is 0.112 kWh per kg.

However to protect the battery and extend battery life vehicle only has 48KWh usable power (vehicle will shut off after battery falls below 15% capacity).
So usable energy density is 48/450 = 0.107 kWh per kg

Hydrogen has roughly 500x the energy density of lithium-ion. Even best lithium-ion batteries in lab are <1 kWh per kg.

Now just comparing hydrogen to lithium ion isn't exactly fair. You need a tank and a fuel cell to turn that into electrical power.

The Honda FCX complete energy system (hydrogen tank, fuel cells, filling port, pressure regulators ect add considerable weight however the entire system still has an energy density of 0.45 kWh per kg.
Now assume a fuel cell stack that is 50% efficient you get 0.225 kWh per kg usable energy.

At 50% fuel cell efficiency H2 has roughly twice the energy density of lithium-ion.
At 70% fuel cell efficiency it is roughly triple.

Anything that can reduce weight of storage tanks will only make Hydrogen have an even higher energy density than lithium-ion.

[happyslug]

19. But we are comparing Hydrogen with gasoline NOT a battery pack

Gasoline has similar high energy content, not as high as Hydrogen but way better then any battery. Thus we may be better off using some form of bio-fuel then Hydrogen. All I am pointing out is the weakness of a Hydrogen future. The better alternative is just get rid of the Automobile but as I can see that is a concept people do NOT even want to think about let alone actually address.

[Statistical]

20. Well that is the problem. Fossil fuels have amazingly energy density.

From a pure efficiency standpoint all the alternatives suck. Fossil fuels are amazing. It is that high energy density and high EROEI that lifted mankind out of darkness. People today rarely die from cold weather, we rarely have mass starvation, the % of income spent on basic necessities is a tiny fraction of what it was 1000 years ago or even 200 years ago.

So if fossil fuels didn't pollute we wouldn't even consider any other method of producing energy especially for transportation.

One potential "half-step" would be CNG combined with fuel cell.

There are two ways to measure energy density by weight and by volume.

Gasoline has about 13kWh per kg and 9.4 kWh per L
CNG (5000 psi) has about 14 kWh per kg and 3.6kWh per L
H2 (5000 psi) has about 40kWh per kg and 0.8kWh per L

So CNG is roughly equivalent to gasoline on weight basis and about 1/3 as dense on Volume basis.
The advantage is that internal combustion engine is about 12%-20% efficient so tank to wheels gasoline engine delivers about 1 to 1.5 kWh per Liter.
A fuel cell & electric motor combined with CNG is 50%+ efficient so it delivers about 1.8kWh per Liter.

Thus you can get gasoline like usable energy densities without anything exotic.
Of course it releases GHG however the combination of cleaner fuel and more efficient (12% vs 50%) means you are reducing GHG by 70%+.

[OKIsItJustMe]

21. Yeah, actually, I rather like direct methanol fuel cells (in theory)

However, hydrogen fuel cells are currently the better bet.

Hydrogen also has the advantage of quickly floating away from a catastrophic leak (rather than running across the ground looking for an ignition source, like gasoline or methanol.)

[Statistical]

4. Most likely fuel stations would simply "make hydrogen" onsite.

To eliminate long term storage losses.

Nobody would make hydrogen and then store it for 90 days. That would be silly and a waste.

Even if we abandoned personal car use completely some form of non-fossil fuel energy will need to be developed. You will never run heavy industrial equipment on batteries. Semitrucks, cargo ships, passenger airlines will all need some form of energy with high power density. Batteries aren't even in the right league.

Oil won't run out but it will be subject to ever escalating prices. DOE estimate for 2035 is $123 per barrel. Note that likely is conservative and is $123 in "real terms" thus excluded inflation. Lets assume 3.0% inflation over next 25 years. That means in nominal terms we are looking at $260 a barrel. $260 a barrel puts gasoline & diesel somewhere around the $8 to $9 mark. While H2 and fuel cells can't compete at $2.00 a gallon gasoline it is foolish to assume they can't at $9 a gallon (plus 25 years more R&D to bring costs down).

[happyslug]

7. I agree to making it on site, but the cost will be high

Please remember something like 50% of total US Energy usage is via Oil and Motor Vehicles. If we assume the 60% efficiency cited above that means to go to a non-oil based transportation system using Hydrogen will require the electrical generation of about twice of what we are using now (And that is ignoring the general increase in electric use over the last 50 years, which is expected to at least double by itself in the next 20 years).

Simply put will will need close to four time the percent electrical production just to break even in 20 years. That not only requires a huge increase in Solar, Hydro, Nuclear power but also coal generation. I am one of those people who do NOT thing such an increase in electrical generation is possible. It is theoretically possible (and using time sharing i.e. charging your car doing low electrical use time period can help) but that is a HUGE increase in energy production. Conservation would be a better way to make sure people have access to electrical power when needed and the best conservation method is to give up the Automobile. People just hate that idea but it will come about within the next 20-40 years but that fear of giving up their automobile and the auto centered life style is what is driving a lot of research into hydrogen, electrical and other non-conventional motor vehicles. For certain applications the motor vehicles will always exist (Ambulances for one) but sooner or later we have to give up the idea that you have to own a car to be a productive member of American Society. A sizable portion of the American Society will fight that tooth and nail to the bitter end.



Lets be clear, 32.1% of all energy (By BTU) was produced by oil, mostly transportation
23.8% of Energy was produced by Natural Gas (heating and some electrical generation)
22.5 % was produced by coal (Mostly Electrical power)
7.3 % by "Renewable" primary Hydro-electric but also Solar (All most all electrical power)
8.5 % produced by Nuclear power (almost all Electrical power)

Of all energy consumption 40.1 % is used to produced electrical power. This includes almost all of the Nuclear, Renewable and Coal production (Total 38.3%, through please note some coal and solar power is used for heating) with the remainder produced by Natural Gas. Oil is almost all used for transportation (Through about 11% of the 32.1 percentage is produced by electricity, mostly Amtrak and other electrical streetcar and bus systems).

http://www.eia.doe.gov/emeu/aer/pdf/pecss_diagram.pdf
http://www.eia.doe.gov/emeu/aer/

Thus my problem, how do we increase electrical output to replace Oil when oil supples almost all transportation needs? The only way I can see it being done is reduce use of transportation and that means most people give up their car. Once you start to look at the numbers that becomes the conclusion and it is an unwanted and unpleasant conclusion to most Americans.

[Statistical]

11. Oh I agree it is a massive challenge however oil will continue to increase in price.

In a couple decades we will look back upon the days of "cheap" $100 oil because it is now $500 per barrel.

Supply will peak and that will require new solutions. The era of cheap fossil fuels is drawing close to an end.

An intermediate step would be to move to natural gas vehicles. Yeah they aren't perfect they do emit GHG however carbon footprint is much lower than oil and we have far more NG resources in this country than oil resources.

Once you have natural gas vehicles making up a sizeable % of vehicle fleet research into fuel cells will explode. Natural gas engine is 12%-20% efficient. Fuel cells are 50%-60% efficient. Get 4x the miles per cubic foot of natural gas using same infrastructure.

Batteries are far more efficient however they have limitations which means they can never be the whole solution. As I indicated in another post you will never have a passenger jet, semi-truck, or cargo ship that runs on batteries. You could make one that runs on natural gas or H2 though.

[OKIsItJustMe]

15. More recent energy flow diagram

http://www.eia.doe.gov/emeu/aer/pdf/pages/sec1_3.pdf