How Artificial Photosynthesis Works

Artificial Photosynthesis Applications

NREL scientist John Turner demonstrates the ability of a photoelectrochemical (PEC) cell to produce hydrogen from water using energy from a light source.
NREL scientist John Turner demonstrates the ability of a photoelectrochemical (PEC) cell to produce hydrogen from water using energy from a light source.
Image courtesy of Warren Gretz, National Renewable Energy Laboratory

Fossil fuels are in short supply, and they're contributing to pollution and global warming. Coal, while abundant, is highly polluting both to human bodies and the environment. Wind turbines are hurting picturesque landscapes, corn requires huge tracts of farmland and current solar-cell technology is expensive and inefficient. Artificial photosynthesis could offer a new, possibly ideal way out of our energy predicament.

For one thing, it has benefits over photovoltaic cells, found in today's solar panels. The direct conversion of sunlight to electricity in photovoltaic cells makes solar power a weather- and time-dependent energy, which decreases its utility and increases its price. Artificial photosynthesis, on the other hand, could produce a storable fuel.

And unlike most methods of generating alternative energy, artificial photosynthesis has the potential to produce more than one type of fuel. The photosynthetic process could be tweaked so the reactions between light, CO2 and H2O ultimately produce liquid hydrogen. Liquid hydrogen can be used like gasoline in hydrogen-powered engines. It could also be funneled into a fuel-cell setup, which would effectively reverse the photosynthesis process, creating electricity by combining hydrogen and oxygen into water. Hydrogen fuel cells can generate electricity like the stuff we get from the grid, so we'd use it to run our air conditioning and water heaters.

One current problem with large-scale hydrogen energy is the question of how to efficiently -- and cleanly -- generate liquid hydrogen. Artificial photosynthesis might be a solution.

Methanol is another possible output. Instead of emitting pure hydrogen in the photosynthesis process, the photoelectrochemical cell could generate methanol fuel (CH3OH). Methanol, or methyl alcohol, is typically derived from the methane in natural gas, and it's often added to commercial gasoline to make it burn more cleanly. Some cars can even run on methanol alone.

The ability to produce a clean fuel without generating any harmful by-products, like greenhouse gasses, makes artificial photosynthesis an ideal energy source for the environment. It wouldn't require mining, growing or drilling. And since neither water nor carbon dioxide is currently in short supply, it could also be a limitless source, potentially less expensive than other energy forms in the long run. In fact, this type of photoelectrochemical reaction could even remove large amounts of harmful CO2 from the air in the process of producing fuel. It's a win-win situation.

But we're not there just yet. There are several obstacles in the way of using artificial photosynthesis on a mass scale.