Hydrogen has the potential to fuel incredibly environmentally clean cars. But making that fuel hasn't been so efficient or economical. Pure hydrogen gas does not occur naturally on Earth, so scientists must devise ways to separate hydrogen from naturally occurring compounds, like H2O. Until now, cars that run on water have been out of reach. But a team of scientists have come up with a different mechanism to produce hydrogen fuel from water. These researchers have created a biomaterial that catalyzes the splitting of the water elements, which they describe in a paper published in the journal Nature Chemistry. The biomaterial, called P22-Hyd, is made up of a modified enzyme, hydrogenase, protected within the protein shell of a bacterial virus. The mechanism goes both ways. P22-Hyd breaks the chemical bonds in H2O to produce hydrogen and oxygen, but it can also combine the two gases to generate power. That reversal is how hydrogen fuel cell cars work. "The reaction runs both ways - it can be used either as a hydrogen production catalyst or as a fuel cell catalyst," study lead author Trevor Douglas, of Indiana University Bloomington said. "You don't need to mine it; you can create it at room temperature on a massive scale using fermentation technology. It's a very green process to make a very high-end sustainable material."