Researchers from Lawrence Berkeley National Laboratory are developing a new bionic leaf to solve the Solar Energy Storage Problem. A leaf that can convert energy from sunlight into an energy-dense fuel, imitating the photosynthetic process of plants. We have covered the artificial leaf concept before. Aside from using a cool new name, the Berkeley project represents a new twist on the technology. A twist that could lead to far greater efficiencies.
The Artificial Leaf Concept
Whether you call it an artificial leaf or a bionic leaf, the basic concept is relatively simple. Normally, a photovoltaic cell generates electricity directly from sunlight. Hydrogen is a chemical reaction that is able to store solar energy. Subsequently, the hydrogen fuel cell will generate electricity.
That sunlight-to-hydrogen chain means you can store solar energy indefinitely. Potentially, in huge quantities. If you think of it as a kind of battery, you’re on the right track. The fuel cell connection means that the intermittent nature of solar energy is not an issue. Neither is its resistance to mobility.
But how do you get there? By dropping a photoelectrochemical cell in a bucket of water, you let it go to work stripping out the hydrogen.
That’s a much more sustainable way to produce hydrogen than the current standard. Nowadays the current standard involves a good deal of fossil energy. Toyota and GM are introducing hydrogen fuel cell vehicle to the mass market. The race is on to develop solar powered hydrogen production at scale.
The Berkeley Bionic Leaf to Solve Energy Storage Problem
If the new bionic leaf to solve the Solar Energy Storage problem certain things should happen. Behind the photoelectrochemical cell is to find the right combination of materials that give you a cost-effective reaction. Otherwise, your bionic leaf is going to sit in the lab and amuse visitors forever.
We’ve been following one solution. An actual leaf-sized artificial leaf was developed. It was produced with a focus on low cost materials to serve households in under-served communities. The absolute efficiency of the cell is not as important as the overall cost. Market electricity consumption is almost negligible. In the latest development, a tweak on the artificial leaf let it function effectively in impure water.
The Berkeley team is also taking cost into consideration. They focus on revving up the performance of the photocathode at the molecular level. The cathode is the part of the cell that generates an electrical current.
The team has been focusing on a hybrid photocathode of gallium phosphide. This is a semiconductor that absorbs visible light. The light, cobaloxime, is a hydrogen-producing catalyst.
Both materials are relatively abundant and inexpensive. Especially when comparing to conventional precious metal catalysts like platinum.
So far, so good. The team just published its latest analysis of the photocathode in the journal Physical Chemistry Chemical Physics. 90% of the generated electrons by the hybrid material were stored in the target hydrogen molecules in the analysis.
The team has also found that the ability of the gallium phosphide to absorb solar energy is far outstripping the ability of the cobaloxime to catalyse a reaction. The result is that only 1.5 percent of the photons that hit the surface get converted into a photocurrent.
So, the search is on for a faster and more efficient catalyst.