Efficient Photocatalytic Production of Hydrogen Peroxide from Water and Dioxygen with Bismuth Vanadate and a Cobalt(II) Chlorin Complex

Efficient photocatalytic production of H₂O₂ as a promising solar fuel from H₂O and O₂ in water has been achieved by the combination of bismuth vanadate (BiVO₄) as a durable photocatalyst with a narrow band gap for the water oxidation and a cobalt chlorin complex (Co^II(Ch)) as a selective electrocatalyst for the two-electron reduction of O₂ in a two-compartment photoelectrochemical cell separated by a Nafion membrane under simulated solar light illumination. The concentration of H₂O₂ produced in the reaction solution of the cathode cell reached as high as 61 mM, when surface-modified BiVO₄ with iron(III) oxide(hydroxide) (FeO(OH)) and Co^II(Ch) were employed as a water oxidation catalyst in the photoanode and as an O₂ reduction catalyst in the cathode, respectively. The highest solar energy conversion efficiency was determined to be 6.6% under simulated solar illumination adjusted to 0.05 sun after 1 h of photocatalytic reaction (0.89% under 1 sun illumination). The conversion of chemical energy into electric energy was conducted using H₂O₂ produced by photocatalytic reaction by an H₂O₂ fuel cell, where open-circuit potential and maximum power density were recorded as 0.79 V and 2.0 mW cm^-2, respectively.