Solar ‘Nanotrees’ Key To Clean Hydrogen Fuel?

A breakthrough at the UC San Diego School of Engineering could offer an environmentally friendly and less expensive way to produce hydrogen—a carbon-free fuel—by taking advantage of a novel tree-like nanostructure. The vertical branch structure, or “nanotree,” is used to maximize solar energy capture and hydrogen gas output.

“With this structure, we have enhanced, by at least 400,000 times, the surface area for chemical reactions,” said Ke Sun, a Ph.D. student in electrical engineering who led the project.


image via UC San Diego

Reporting in the journal Nanoscale, the team said they are building a forest of tiny nanowire trees in order to cleanly capture solar energy in a way that mimics the way trees absorb energy.

Like the famous work by Daniel Nocera, artificial photosynthesis is the inspiration for the UC San Diego Jacobs School of Engineering team working under Deli Wang, professor in the Department of Electrical and Computer Engineering. (We’ve also seen MIT’s Andreas Mershin devise an “electric nanoforest” in the quest for cheap solar power.)

In photosynthesis, as plants absorb sunlight they also collect carbon dioxide (CO2) and water from the atmosphere to create carbohydrates to fuel their own growth.

Wang’s team also hopes to mimic this natural photosynthesis process to capture CO2 from the atmosphere, reducing carbon emissions, and convert it into hydrocarbon fuel.

Most of this promising hydrogen research is focused on substituting clean energy with no greenhouse gas byproduct for today’s fossil-fueled hydrogen splitting. Wang’s “3D branched nanowire array” uses a process for separating water into oxygen and hydrogen called photoelectrochemical water-splitting that uses sunlight.

Susan Kraemer enjoys writing to publicize the many great solutions for climate change that we can find if we just put our minds to it. She covers renewable policy and clean energy for CleanTechnica and GreenProphet and green building at HomeDesignFind. She recently moved home to Waiheke Island where her writing is now powered by the 80% renewable electricity that powers New Zealand.


  • Reply March 11, 2012


    Nothing about the cost?  How can it be called a “breakthrough?”

    More cheerleading, I guess.

    • Reply March 15, 2012

      Pete Danko

      Indeed, we cheer for scientists doing great research. Unabashedly.

    • Reply March 17, 2012

      Susan Kraemer

      AWW, generally, research at the pure research level is too far from commercialization to estimate the cost in mass production. In rare cases, like when an industry leader the size of a Suntech makes a research advance – then, they can get it into production, and then, the cost (or more typically, cost reduction) IS something that I would cover, as soon as they reveal it.

      But also, in general, efficiency advances are typically cost reductions. Savvy investors find the likeliest to advance. We just don’t know how much of a cost cut till later than the intial “breakthrough” stage. But like Pete says, without great researchers, there’s no great breakthrough, no cost cuts to status quo.

  • Reply March 16, 2012


    should be using this time to develop green energy, and green jobs. Big Oil keep promoting clean coal, and natural gas, sand tars, and oil and gas fracking operations while saying that photo voltaic, and wind
    doesn’t work. We should be calling them out on this. How about internal
    combustion hydrogen cars? With some injector modification Hydrogen can be fired in a conventional internal
    combustion engine. With this technology hydrogen could have a truly neutral or even a positive effect on reducing carbon in the atmosphere. Long term this is what future investment in fuel technology should look like. Take away the oil companies subsidies and lets get back our environment, and create our ability to produce sustainable energy local. Costs can be worked out at scale just like oil production.

  • Reply March 19, 2012

    Lewis Goudy

     >Hydrogen can be fired in a conventional internal
    combustion engine.<

    Great stuff once it gets to the engine.  The problem is the fuel tank.  Because it is so light it must be highly compressed to carry much energy per liter of tank.  Because it is so small it will, under high pressure, not only find physical paths through common steel (microporosity) but also dissolve right into the metal and exit to the atmosphere.  It is extremely hazardous (widest explosive range of any flammable gas) and difficult to deal with in terms of bulk transport and storage.  If you are going to go to the trouble of vehicular application it makes more sense to use fuel cells rather than IC engines.  I think the best way to use hydrogen in IC vehicular applications is to dissolve it in propane, which will hold quite a bit of it while remaining easy to deal with.  A propane-fueled plug-in hybrid could use off-peak grid power to enhance range by using dissolved hydrogen as a mezzanine level kwh sink after the on-board battery was fully charged.

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