Seawater usable for production and consumption of hydrogen peroxide as a solar fuel

Hydrogen peroxide (H 2 O 2) in water has been proposed as a promising solar fuel instead of gaseous hydrogen because of advantages on easy storage and high energy density, being used as a fuel of a one-compartment H 2 O 2 fuel cell for producing electricity on demand with emitting only dioxygen (O 2) and water. It is highly desired to utilize the most earth-abundant seawater instead of precious pure water for the practical use of H 2 O 2 as a solar fuel. Here we have achieved efficient photocatalytic production of H 2 O 2 from the most earth-abundant seawater instead of precious pure water and O 2 in a two-compartment photoelectrochemical cell using WO 3 as a photocatalyst for water oxidation and a cobalt complex supported on a glassy-carbon substrate for the selective two-electron reduction of O 2. The concentration of H 2 O 2 produced in seawater reached 48 mM, which was high enough to operate an H 2 O 2 fuel cell.