Nanowire Forests Use Sunlight To Split Water

An anonymous reader sends this excerpt from IEEE Spectrum's Nanoclast blog: "One of the fundamental problems with fuel cells has been the cost of producing hydrogen. While hydrogen is, of course, the most abundant element, it attaches itself to other elements like nitrogen or fluorine, and perhaps most ubiquitously to oxygen to create the water molecule. ... Now researchers at University of California, San Diego have developed a quite different approach to mimicking photosynthesis for splitting water molecules by using a 3D branched nanowire array that looks like a forest of trees. ... The nanowire forest [uses] the process of photoelectrochemical water-splitting to produce hydrogen gas. The method used by the researchers, which was published in the journal Nanoscale (abstract), found that the forest structure of the nanowires, which has a massive amount of surface area, not only captured more light than flat planar designs, but also produced more hydrogen gas."

Comments

Hmmm... ZnO band gap is 3.37 eV

[dsgrntlxmply]

The experiment is interesting as regards the benefits of the nanostructure of the materials, but the 3.37 eV band gap of ZnO must be kicked across by a photon of no less energy (no longer wavelength) than 367 nm: ultraviolet.

The good news is that you have plenty of energy relative to 1.25eV minimum needed to split water. The bad news is that you need high energy photons that are relatively scarce in sunlight by the time it reaches the earth's surface.

Re:Solar cells?

[Skapare]

I've heard that concentrating light on a solar cell increases the efficiency. So if a concentrator captures 4x light from a 4x aperture onto the same size solar cell surface, you get more electrical energy than just 4 like surfaces. If that's true, the intensity is doing something to avoid the losses, which I assume are heat losses, which should normally be higher with a concentration due to the higher temperature. Any truth or applicability to that?

The Holy Grail of solar power is, of course, to turn 100% of sunlight energy (across a huge spectrum) into an energy form that can be directly used. So I'm looking for that (without all that science background to know the details about things that can really work. My last look into this was trying to find if anyone was building nano Sterling Engines.