2:00 PM - 2:30 PM
[15p-A24-3] Photocatalytic and photo-electrochemical production of hydrogen and valuable oxidation reagents using oxide semiconductors
Keywords:photoelectrode, solar energy, hydrogen
Although various water splitting systems using oxide semiconductor photoanodes have been investigated, almost all these systems focused solely on production and recovery of H2 energy; there has been little focus on the recovery of oxidation products such as O2, which is simultaneously evolved during water splitting. We prepared a porous and thick photoelectrode of WO3 or BiVO4 to realize the recovery of H2 and high-value-added oxidation reagents with efficient solar energy conversion. The WO3 photoelectrode enabled the production and accumulation of O2, S2O82-, Ce4+ or IO4- as oxidation products. Most notably, S2O82-, which possesses the highest oxidizability among all peroxides, was generated with high applied bias photon-to-current efficiency (ABPE H2 S2O82- = 2.2%) and Faraday efficiency (ca. 100%) on irradiation from the back side of the photoelectrode. Designs of tandem photoelectrode system combining dye-sensitized solar cell (DSSC) were also challenged for realization of stand-alone system. 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 production of H2 and S2O82-. Furthermore, we investigated oxidative H2O2 production from water on a WO3/BiVO4 photoanode simultaneously with production of hydrogen on a Pt cathode in bicarbonate electrolyte even at a voltage far lower than the theoretical electrolysis voltage (1.77 V) under simulated solar light. An unprecedentedly efficient simultaneous production and accumulation of H2O2 was achieved in 2.0 M KHCO3 at low temperature, and the maximum selectivity, accumulated concentration and turnover number (TON) of H2O2 generated reached ca. 54%, 2 mM and 108, respectively. The role of bicarbonate ion for H2O2 production is investigated.