Most of the current hydrogen production in the U.S. is carried out by steam reforming natural gas (methane), which involves reacting steam with methane to generate H₂. To make hydrogen a viable fuel source, more efficient ways of producing hydrogen on the large scale will be needed. Many scientists are currently investigating chemical and biological catalysts capable of carrying out a process called water splitting, which is the production of H₂ and O₂ from water (H₂O). Water splitting may have the potential to make hydrogen into a viable fuel source for vehicles.