Abe Ryu, Sayama Kazuhiro, Sugihara Hideki
National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan.
J Phys Chem B. 2005 Aug 25;109(33):16052-61. doi: 10.1021/jp052848l.
A new type of photocatalytic reaction that splits water into H2 and O2 was designed using a two-step photoexcitation system composed of an iodate/iodide (IO3-/I-) shuttle redox mediator and two different photocatalysts, one for H2 evolution and the other for O2 evolution. Photocatalytic oxidation of water to O2 and reduction of IO3- to I- selectively proceeded with good efficiencies over TiO2-rutile and Pt-WO3 photocatalysts under UV and visible light irradiations, respectively. The O2 evolution selectively proceeded even in the presence of a considerable amount of I- in the solutions, although the oxidation of water is thermodynamically less favorable than oxidation of I-. Both the adsorption property of IO3- anions and the oxidation property of the photocatalysts are doubtless responsible for the selective oxidation of water. On the other hand, photocatalytic reduction of water to H2 and oxidation of I- to IO3- proceeded over Pt-TiO2-anatase and Pt-SrTiO3:Cr/Ta (codoped with Cr and Ta) photocatalysts under UV and visible light, respectively. The combination of two different photocatalysts results in a stoichiometric evolution of H2 and O2 via the redox cycle of IO3- and I-. The photocatalytic water splitting under visible light irradiation (lambda > 420 nm) was demonstrated by using the Pt-SrTiO3:Cr/Ta, Pt-WO3, and IO3-/I- shuttle redox mediator.
利用由碘酸盐/碘化物（IO₃⁻/I⁻）穿梭氧化还原介质和两种不同光催化剂组成的两步光激发系统，设计了一种将水分解为H₂和O₂的新型光催化反应，一种光催化剂用于析氢，另一种用于析氧。在紫外光和可见光照射下，水在TiO₂-金红石型和Pt-WO₃光催化剂上分别选择性地高效进行光催化氧化生成O₂以及IO₃⁻还原为I⁻的反应。即使溶液中存在大量的I⁻，析氧反应仍选择性地进行，尽管水的氧化在热力学上比I⁻的氧化更不利。IO₃⁻阴离子的吸附性能和光催化剂的氧化性能无疑是水选择性氧化的原因。另一方面，水在Pt-TiO₂-锐钛矿型和Pt-SrTiO₃:Cr/Ta（共掺杂Cr和Ta）光催化剂上分别在紫外光和可见光下进行光催化还原生成H₂以及I⁻氧化为IO₃⁻的反应。两种不同光催化剂的组合通过IO₃⁻和I⁻的氧化还原循环实现了H₂和O₂的化学计量析出。使用Pt-SrTiO₃:Cr/Ta、Pt-WO₃和IO₃⁻/I⁻穿梭氧化还原介质证明了在可见光照射（λ>420 nm）下的光催化水分解。
