Researchers at the University of Michigan and the McGill University have created a machine that replicates the process of photosynthesis by effectively splitting fresh or salt water into hydrogen so it can be used in fuel cells. The resulting hydrogen is as of yet the cleanest burning fuel because it only produces heat and water as emissions. Hydrogen is the lightest and most abundant element in the universe, making up 74% of all nuclear matter.

“If we can directly store solar energy as a chemical fuel, like what nature does with photosynthesis, we could solve a fundamental challenge of renewable energy,” said lead researcher Zetian Mi.

Small towers of gallium nitride generate an electric field to turn photons into free charges, which divide water into its two component elements, oxygen and hydrogen. The importance of this finding is that previous methods of producing hydrogen fuel, steam reforming and electrolysis, were not environmentally friendly. In contrast with previous solar splitters, which had only reached 1 percent efficiency, Mi’s team managed to achieve a 3 percent solar-to-hydrogen efficiency.

Steam reforming uses methane and water to produce carbon monoxide and hydrogen, and the remaining carbon monoxide reacts with water to produce carbon dioxide and hydrogen. The resulting carbon dioxide is a greenhouse gas. Electrolysis uses an electric current to split hydrogen and oxygen from water, but often the electricity needed comes from nonrenewable sources.

One of the greatest potential applications of using hydrogen as fuel is with hydrogen power vehicles. In the United States, several vehicle manufacturers have begun making light-duty hydrogen fuel cell electric vehicles available in select regions like southern and northern California where there is access to hydrogen fueling stations. Test vehicles are also available in limited numbers to select organizations with access to hydrogen fueling stations.

Most hydrogen-fueled vehicles are automobiles and transit buses that have an electric motor powered by a fuel cell. A few of these vehicles burn hydrogen directly. The high cost of fuel cells and the limited availability of hydrogen fueling stations have limited the number of hydrogen-fueled vehicles. Furthermore, refueling stations are an important concern because customers will not buy hydrogen-fueled cars if refueling stations aren’t readily available, and companies won’t build refueling stations if there are no customers driving hydrogen-fueled cars.