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.