Gold Amount Dependence of Red Light Responsive Z-Scheme Photocatalyst on Water-Splitting Activity Using Gold Prepared By Sputtering in Ionic Liquid

摘要

Since the Fujishima effect was reported in 1972, researches on photocatalytic water splitting using sunlight have been progressing as a method for producing hydrogen (H_2), which attracts attention as an alternative clean energy source for fossil fuels. For the effective use of sunlight, we have investigated an all-solid-state Z-scheme photocatalyst that can be sensitive to long-wavelength, low-energy light and can decompose pure water (without chemicals as a sacrificial agent or pH adjuster). In our previous study, we fabricated the Z-scheme photocatalyst, consisting of zinc rhodium oxide (ZnRh_2O_4) and bismuth vanadium oxide (Bi_4V_2O_(11)) as a H_2- and oxygen (O_2)-evolution photocatalyst, respectively, and gold (Au) as a solid redox mediator (ZnRh_2O_4/Au/Bi_4V_2O_(11)). The photocatalyst has successfully achieved the overall pure water splitting irradiated with red light (wavelength 700 nm) via Au, which mediated the transfer of photoexcited electrons from the conduction band (CB) of Bi_4V_2O_(11) to the valence band (VB) of ZnRh_2O_4. Then, photogenerated holes in the VB of Bi_4V_2O_(11) and photoexcited electrons in the CB of ZnRh_2O_4 effectively oxidized and reduced water, respectively, to achieve overall water splitting.