Photoelectrochemical Reaction for the Efficient Production of Hydrogen and High-Value-Added Oxidation Reagents

A porous and thick photoelectrode of WO3 in the monoclinic phase was prepared to realize the recovery of H-2 and high-value-added oxidation reagents with efficient solar energy conversion. The WO3 photoelectrode enabled the efficient production and accumulation of O-2, S2O82-, Ce4+, and IO4- as oxidation products. Most notably, S2O82-, which possesses the highest oxidizability among all the peroxides, was generated with high applied bias photon-to-current efficiency (2.2%) and faraday efficiency (approximate to 100%) upon irradiation from the back side of the photoelectrode. The design of a tandem photoelectrode system combining a dye-sensitized solar cell (DSSC) was also challenged for the realization of this photoelectrode system without external bias. A high solar energy conversion efficiency (5.2%) was achieved in the tandem system comprising the WO3 photoelectrode connected to two DSSCs with a near-IR-utilizing dye in series for the production of H-2 and S2O82-.