Direct conversion of sunlight into hydrogen

I think you are thinking of a photocatalytic conversion process...

..."Photocatalytic water splitting relies on a photocatalyst to facilitate the reaction. Photocatalysts are made from metal oxides, and they need to perform the water splitting reaction many times over without degrading.

Professor Kazunari Domen and his team from the University of Tokyo are researching how to make better, longer-lasting photocatalysts. They have developed an aluminium-doped SrTiO3 catalyst, which retains 80% of its initial activity after 55 days of continuous use.

This catalyst has been used before, but was known to decompose quite quickly with use. During photocatalytic water splitting, the UV light generates negatively-charged electrons, and corresponding positively-charged 'holes' in the catalyst. 'Holes' have strong oxidising properties, and it is thought that if there are too many of them they can damage the photocatalyst.

To solve this problem, the researchers have added a co-catalyst called cobalt oxyhydroxide, which prevents holes from accumulating. This makes the catalyst much more durable and long-lasting."...

https://www.rsc.org/news-events/journals-highlights/2019/feb/fuel-from-sunlight/#:~:text=In%20the%20same%20way%20that,referred%20to%20as%20artificial%20photosynthesis.

Renault reveals electric-hydrogen hybrid concept car, says it will have range of up to 497 miles

https://www.cnbc.com/2022/05/20/renault-says-electric-hydrogen-concept-will-have-497-mile-range.html#:~:text=Sustainable%20Energy-,Renault%20reveals%20electric%2Dhydrogen%20hybrid%20concept%20car%2C%20says%20it%20will,of%20up%20to%20497%20miles&text=The%20design%20for%20Renault's%20Scenic,located%20at%20the%20vehicle's%20front.

So a combination of batteries and a hydrogen fuel cell seems the way to go....

The science project I saw was very simple,nothing but water and iron powder.It may not have been efficient,but it worked in principle.This was a high school science project,so it was not very sophisticated.

I know many improvements in the method have been made,as well as development of hydrogen engines.It seems that chemical storage(metal Hydrides, or absorptives) of hydrogen is the most compact method of storage,because hydrogen is very hard to store in a gaseous or liquid state.In addition to batteries,super capacitors may have a role in future Ev's to give sudden boost of power when required...I think the problems will be solved in the future,and 50 years from now,people will look back at how primitive we were.

(Unless of course,WWIII kicks us back to the stone ages.)

Here is something you might find interesting:

Highly efficient hydrogen gas production using sunlight, water and hematite (phys.org)

That is an interesting and promising article you have there. Buried in that article are some cryptic numbers that explain how close this approach gets to becoming a viable approach for industrial use. The article proffers that at least a 10% solar energy conversion is required for industrial use. They also claim the theoretical limit for this approach is 16% energy conversion. This latest configuration achieved 42% of the theoretical limit. Simple ratio math puts the solar energy conversion at 16%*.42=6.72%. This is promising but not a high enough conversion rate, yet.

I have great hopes for the future of energy generation and consumption.

Look how much progress has been made since the Model T.

Henry Ford did not start with a Town Car.

Perhaps one day we will be able to harness the electricity from the geomagnetic field that envelops the Earth.

I think this may have been Tesla's dream of free energy,but many of his notes have been "lost" and his towers have been turned into scrap.

Nearly everything we take for granted now that is run by A/C electricity is due to this genius.

Hardly any credit given to Tesla,even by the Smithsonian Institute.

A real unsung hero in my book.

Well I think ammonia is the best storage method for hydrogen....

..."Liquid ammonia is able to store hydrogen in volumes much higher (121 kg-H2/m3) than liquid hydrogen (70.8 kg-H2/m3), which is about 1.7 times as high. Liquid ammonia can be stored at relatively low pressure (0.99 MPa at a temperature of 25 °C), which is significantly lower than that of compressed hydrogen."Jun 12, 2020

Yeah, that's a lot....

The downside is that anhydrous ammonia is considered a hazardous chemical, which is probably why it is not used as a refrigerant...

AMMONIA HAZARDS

Lungs - Inhalation can quickly burn the nose, throat and all the way down through the upper chest.

Eyes - It can cause irritation and even permanent damage or blindness.

Skin - Ammonia is corrosive. If there's contact with flesh, it will eat it away. If the level of exposure is high enough it can result in death.

And finally, ammonia is very flammable.

Don't know if this is a show stopper...

Ammonia Hazards – The Safety Brief (creativesafetysupply.com)

There are several advantages to using ammonia as a hydrogen storage medium...one, the infrastructure is already in place, there are about 150 million tons produced annually...two, it's current production methods are energy intensive and produce an inordinate amount of co2...so switching to green production methods will help eliminate waste and greenhouse gas emissions...three, it takes fossil fuels out of the fertilizer loop, most of the ammonia produced is used as fertilizer, so food production is tied to fossil fuel production, which causes price volatility and destabilization....

Ammonia is still used as a refrigerant in China, but I don't recommend it...

https://cen.acs.org/environment/green-chemistry/Industrial-ammonia-production-emits-CO2/97/i24

I have worked around NH3.It has an affinity for moisture,and will travel upwind to get to it.The first thing to be attacked is the moist parts of you body,nose,eyes,armpits,groin,and of course,your lungs.When you inhale it,it feels like menthol at first,then the heat sets in.

It is highly caustic(around 11Ph),and as well has a very low temperature of -28F degrees,so skin contact with the liquid will cause frost bite and cause a caustic burn at the same time..Very hard to treat and slow to heal.

It becomes explosive at around 25%,but no one can tolerate that level,so they will either evacuate or die before it reaches that level.

Household ammonia is only around 5%,so it is easy to imagine the difference.

There are still many industries that use ammonia for cooling,and campers with LP powered refrigerators use it also.

Ammonia can be safe if handled properly,and could be a good method to store hydrogen.Only a small amount would be used, on demand.Even a small leak would be immediately detected,and sulfur sticks are used to detect leaks also.The are lit and begin to faintly smoke,and if ammonia reaches it,even in minute amounts,the smoke will increase dramatically and be very white.This is used to detect the source of a leak.

Thousands of farmers use liquid ammonia for their crop,and know how to handle it safely,so it is a very mature technology.

Although there are jurisdictions around the world that prohibit (or greatly restrict) ammonia as a refrigerant, it still remains very commonplace.

The "extremely flammable" designation is dubious, but that could be too lengthy a discussion for here and now. (Maybe later.)

"which is probably why it is not used as a refrigerant."

Ammonia (R717) is used extensively as a refrigerant in many industries - food storage and freezing, gas processing, refineries, chemical plants etc..

Tesla battery pack module 5.3 kwh...

https://stealthev.com/product/tesla-module/

..."n the study, Haile and her research team report they are able to conduct the ammonia-to-hydrogen conversion using renewable electricity instead of fossil-fueled thermal energy because the process functions at much lower temperatures than traditional methods (250 degrees Celsius as opposed to 500 to 600 degrees Celsius).

Second, the new technique generates pure hydrogen that does not need to be separated from any unreacted ammonia or other products. Third, the process is efficient because all of the electrical current supplied to the device directly produces hydrogen, without any loss to parasitic reactions.

As an added advantage, because the hydrogen produced is pure, it can be directly pressurized for high-density storage by simply ramping up the electrical power.

To accomplish the conversion, the researchers built a unique electrochemical cell with a proton-conducting membrane and integrated it with an ammonia-splitting catalyst.

"The ammonia first encounters the catalyst that splits it into nitrogen and hydrogen," Haile said. "That hydrogen gets immediately converted into protons, which are then electrically driven across the proton-conducting membrane in our electrochemical cell.

By continually pulling off the hydrogen, we drive the reaction to go further than it would otherwise. This is known as Le Chatelier's principle. By removing one of the products of the ammonia-splitting reaction -- namely the hydrogen -- we push the reaction forward, beyond what the ammonia-splitting catalyst can do alone."

The hydrogen generated from the ammonia splitting then can be used in a fuel cell. Like batteries, fuel cells produce electric power by converting energy produced by chemical reactions. Unlike batteries, fuel cells can produce electricity as long as fuel is supplied, never losing their charge. Hydrogen is a clean fuel that, when consumed in a fuel cell, produces water as its only byproduct."...

https://www.sciencedaily.com/releases/2020/11/201118141718.htm

Sounds like the by product, the nitrogen would be easily converted for agricultural use,or used as-is.No waste,everything used.

I can imagine farm tractors with on board conversion with hydrogen running the engines,and the nitrogen injected into the soil.Nothing gone to waste.

It would be good to have a link to the article about the <...high school science project...> as part of this thread.

Photodissociation - Wikipedia

Nah, it's so much more fun watching random fantasies battle for superiority.

I remember reading about a talking lion kept in a clothes closet. Why don't we just put a mating pair of all of the endangered species in clothes closets so we no longer have to care about what we do to the planet?

Done...

IVF works for mammals if a suitable surrogate womb still exists. It's not done yet.

https://www.biospace.com/article/artificial-womb-technology-benefits-animal-subjects-could-it-work-in-humans-/

Portugal switches on first solar-to-hydrogen plant

https://www.pv-magazine.com/2022/11/10/portugal-switches-on-first-solar-to-hydrogen-plant/