Faking It This Fall

Being a native of upstate New York, Fall is one of my favorite times of the year. The trees always look so beautiful when they're all different colors and who can resist that crisp morning chill?

^{Image Credit: Brainerd.com}

The leaves change color due to the reduction of sunlight. Sunlight is used to turn water and carbon dioxide into oxygen and glucose (a process known as photosynthesis). The shortage of sunlight and water causes a reduction in the supply of chlorophyll--used in photosynthesis--and thus the green color caused by the chlorophyll fades away leaving the yellow and red colors.

Scientists at MIT have created an "artificial leaf" which is able to turn the energy of sunlight into chemical fuel that can be stored for later use. The artificial leaf is very thin and made of earth-abundant elements. The device resembles a silicon solar cell and is made of silicon, cobalt, and nickel. There are three layers to the 'artificial leaf'; the semiconducting silicon is bounded on one side by a layer of cobalt- based catalyst, which releases oxygen, and the other side is coated with a layer of nickel-molybdenum-zinc alloy, which releases hydrogen from the water molecules. The lightweight device has no external wires or control circuits for operation.

^{Image Credit: Daniel Nocera}

The 'leaf' works while submerged in water, and exposed to sunlight. The device quickly releases oxygen as a stream of bubbles from one side, and a stream of hydrogen bubbles from the other side. A barrier can be used to separate the two sides so the gases can be collected and stored. The gases can then be used to deliver power in fuel cells, which require water to deliver an electric current.

The applications for the 'artificial leaf' are still being explored, but one such application would be commercialization for individual homes to make energy simple and inexpensive enough to be widely adopted. There is still work being done to optimize the system but progress is being made to lower costs and improve the efficiency.

Currently, the artificial leaf can redirect about 2.5 percent of the energy from sunlight into hydrogen production in its wireless form. Adding wires increases efficiency to 4.7 percent, whereas commercial solar cells have 10 percent efficiency. Here is a video of the 'artificial leaf' working.