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Scientists Achieve Perfect Efficiency For Water-Splitting Half-Reaction (phys.org)
Dthief writes: Splitting water is a two-step process, and in a new study, researchers have performed one of these steps (reduction) with 100% efficiency. The results shatter the previous record of 60% for hydrogen production with visible light, and emphasize that future research should focus on the other step (oxidation) in order to realize practical overall water splitting. The main application of splitting water into its components of oxygen and hydrogen is that the hydrogen can then be used to deliver energy to fuel cells for powering vehicles and electronic devices. The process involves exposing the water to a mass of platinum-tipped nanorods, with visible light driving the reaction.
The 100% efficiency refers to the photon-to-hydrogen conversion efficiency, and it means that virtually all of the photons that reach the photocatalyst generate an electron, and every two electrons produce one H2 molecule. At 100% yield, the half-reaction produces about 100 H2 molecules per second (or one every 10 milliseconds) on each nanorod, and a typical sample contains about 600 trillion nanorods.
the cheapest way to store the oxygen so you can use it later is to not store it, releasing it into the atmosphere, and later just use "air" for the reaction. :-)
Not when you consider the total cost. Air is about 78% Nitrogen, which leads to a lot of inefficiency. Most engines will run much more efficiently with straight O2, or even O2 and some other substance such as injected water. Coal burning power plants that do carbon sequestration use air stripped of N2 so they don't have to separate the CO2 from the N2 in the exhaust. Nitrogen in a combustion chamber also leads to a lot of nasty pollutants that are difficult and expensive to remove. If you are producing pure O2, just venting it into the air is a big waste.
Hydrogen sells for about $1/Kg today. How much cheaper will it get with this process?
-jcr
The only title of honor that a tyrant can grant is "Enemy of the State."
A hydrogen economy would be useless for exactly that reason. To store hydrogen, you need exotic materials and high-energy cooling systems. Hydrogen leaks through sealed steel; you'd need to use a lot of energy to keep a hydrogen storage unit idle. This is okay when you're making, shipping, burning; but it's not okay when you fill up your gas tank once a month.
If they could combine the hydrogen with CO2 and make O2+C4H, they could use methane to drive fuel cells or internal combustion. You can actually store methane.
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Hydrogen is a terrible energy source. The gas has very low energy density (big gas tank), compressing it takes a lot of energy, and it leaks through holding tanks. The money that is being wasted on the hydrogen economy should be directed into broadcast energy or putting power rails into the roads.
How do you figure that's carbon neutral? You're still converting all that geologically sequestered carbon into CO2.
Just because you're scrubbing it from the exhaust and temporarily storing it somewhere doesn't mean it's not there. So far as I've heard, we've yet to come up with a way to store CO2 in the long term. Pumping it into the ground is only a temporary buffering solution, as it begins to leak out almost immediately. Undersea storage is a bit more effective, but much more expensive, and has a devastating effect on the fragile sea-bottom ecosystem with unknown long-term consequences.
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False.
Pure O2 is the only thing which breaks the fire triangle (fires require oxygen, fuel, and ignition sources)
It's oxygen, so that's one corner of the triangle.
It turns almost anything into a fuel and handling it is incredibly difficult because of this. For example pure O2 pipelines have "fuses" put into them which is basically a section of teflon pipe with high pressure water jets directed at it because the metal pipework itself becomes a fuel in the presence of pure O2. Most things which aren't a fuel in normal air burn spectacularly in the presence of concentrated O2. That's the second corner of the triangle.
Also pure O2 is easily ignited by any particles in the O2 stream. There's a separate specification for construction and cleaning of O2 carrying systems on top of the standard pipe spec because of this, as well as special ordering requirements for any equipment used in O2 services. If that isn't bad enough it can spontaneously combustion due to adiabatic compression by something as simple as a valve moving too quickly. That's the final corner of the triangle.
In industry O2 is handled like an explosive and highly volatile substance. The exception is when it is in stationary containment (i.e. a gas cylinder). In most plants handling pure O2, the pipework has special identification on it to ensure people stay the heck away from it.