Image courtesy of Nanoptek, Inc.
The Massachusetts-based energy startup has developed a new process for producing hydrogen fuel from water using just sunlight and a proprietary photocatalyst. Reporting in Technology Review, Kevin Bullis describes its main advantage as being two-fold: it is "cheap enough to compete with the cheapest approaches used now, which strip hydrogen from natural gas, and it has the further advantage of releasing no carbon dioxide."
Nanoptek's technology centers on the use of titania, or titanium dioxide, a relatively cheap and abundant material, to absorb solar energy; according to John Guerra, the startup's founder and CEO, its engineers were able to modify the material so as to enable it to absorb more sunlight, rendering the process of splitting water to make hydrogen much more cost-effective.To boost its absorption efficiency, Nanoptek's engineers used a technique often employed by the semiconductor industry to "strain" the titania; chip makers have long relied on this method to alter a material's electronic properties - choosing either to press together or pull apart its atoms to obtain the desired result. Guerra explained that less energy is required to split water when titania's atoms are pulled apart, allowing for the use of both high energy UV light and low energy visible light. The company's engineers deposited a coating of titania on dome-like nanostructures to get the atoms to pull apart.
Here is how Nanoptek's website describes the process:
"Nanoptek has developed a titania photoelectrode that is low cost, has a long lifetime, and higher efficiency in converting sunlight into hydrogen. Nanoptek has developed a way to use nano-structures (as shown in our logo) to cause large local nano-scale stresses in the titania. This stretches the titania crystal lattice so that electrons are held less tightly in the lattice and so can be knocked out of the titania with light of lower energy, meaning visible. These electrons then drive the hydrogen production. This is known as "bandgap engineering" and causes Nanoptek's titania photocatalyst to be photoactive well into the visible blue, and so is 6X more efficient in sunlight than native titania, which requires the sparse ultraviolet (UV) part of the solar spectrum."
Unlike processes that rely on natural gas or electrolysis, which are more costly and inefficient, Nanoptek's approach is cheap and produces no carbon dioxide emissions. By being located close to its customers, the company's technology would also significantly cut back on transportation costs. In addition to supplying fuel-cell vehicles, Nanoptek's process - if it proves to be as cheap and efficient as Guerra claims - could be used for the nighttime storage of solar energy.