Almost 18 months ago, HyperSolar, Inc., a company based in Santa Barbara, Calif., unveiled its ambitious plans for artificial photosynthesis. The announcement promised “the world’s first nanotechnology-based, zero-carbon process for the production of renewable hydrogen and natural gas.” The company was so confident that, two months later, it promised to publicly chronicle its progress toward the lofty goal.
Other companies have tried—and failed—to find an artificial photosynthesis process that can split water into hydrogen and oxygen and do it economically. Around the same time that HyperSolar promised to chronicle their efforts, Sun Catalytix determined that its process for splitting water just didn’t make economic sense when they crunched the numbers.
In the journal Nature, the maker of Sun Catalytix’s prototype explained the dreary economics:
“Hydrogen from a solar panel and electrolysis unit can currently be made for about US$7 per kilogram, the firm estimates; the artificial leaf would come in at US$6.50. (It costs just $1-2 to make a kilogram of hydrogen from fossil fuels.) With the prices of solar cells dropping all the time, the firm is not going to make a heavy investment that's unlikely to pay off. Instead, it is looking at cheaper designs—but these require yet-to-be-invented semiconductor materials.”
When I didn’t hear any updates from HyperSolar on how its grand project was progressing this year, I began to suspect that they had encountered these same numbers and had a second thought. I guess I was wrong—the company just sent out a press release detailing its success in achieving the 1-volt milestone. To date inexpensive silicon solar cells are the most inexpensive and abundant, but their 0.7 volt per cell is not enough to split water.
HyperSolar's 1 volt per cell is still short of the 1.5 volts realistically needed to split water into hydrogen and oxygen, but the 1 volt number does represent a steady progression, according to the company. HyperSolar managed to increase the voltage from 0.2 volts eight months ago to .75 volts three months ago. At that rate of increase, one could expect that the company could achieve the 1.5 volts in another six months.
“Our cutting-edge research program at the University of California Santa Barbara led by Dr. Syed Mubeen Hussaini continues to make impressive progress,” stated Tim Young, CEO of HyperSolar, in the press release. “The 1.0 volt milestone is very exciting in that it provides us with a clear and encouraging roadmap to reach the 1.5 volts needed for water splitting. The semi-conductor materials used are very inexpensive, which gives us confidence that a low cost system is possible. The process to make this novel solar cell is equally exciting in that it is a simple solutions-based chemistry process. It does not require conventional expensive semiconductor processes and facilities. It was literally made in a beaker.”
The key to HyperSolar’s proposed technology will be a nanoparticle made from low-cost semiconductor materials. In the company’s original roadmap for milestones, they were supposed to design this nanoparticle within the first year. It’s not clear from this press release whether that design has been settled upon, except to explain that each nanoparticle: “is a complete hydrogen generator that contains a novel high voltage solar cell bonded to chemical catalysts by a proprietary encapsulation coating.”
It is interesting that the company is providing key metrics for determining whether the system will work, but it would be good to have a better sense of where they are in developing the nanoparticle that forms the basis of this technology.
Dexter Johnson is a contributing editor at IEEE Spectrum, with a focus on nanotechnology.