Hydrogen as a fuel source, rather than hydrocarbons like oil and coal, offers many benefits. Burning hydrogen produces harmless water with the potential to eliminate carbon dioxide emissions and their environmental burden. In pursuit of technologies that could lead to a breakthrough in achieving a hydrogen economy, a key issue is making hydrogen cheaply. Using catalysts to split water is the ideal way to generate hydrogen, but doing so usually requires an energy input from other chemicals, electricity, or a portion of sunlight which has high enough energy.