Hwang Dong Won, Kim Hyun Gyu, Lee Jae Sung, Kim Jindo, Li Wei, Oh Se Hyuk
Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), San 31 Hyoja-dong, Pohang 790-784, Republic of Korea.
J Phys Chem B. 2005 Feb 17;109(6):2093-102. doi: 10.1021/jp0493226.
In the search for efficient photocatalysts working under visible light, we have investigated the effect of cation substitution on a layered perovskite, La2Ti2O7. Among various metal dopants, only Cr and Fe induced intense absorption of visible light (lambda > 400 nm), and only these catalysts produced H2 photocatalytically from water in the presence of methanol under visible light irradiation (lambda > 420 nm). The polymerized complex method was found to be more efficient for fabrication of the present catalysts producing a more homogeneous structure than the solid-state reaction. The characterization by XRD, UV-vis DRS, XPS, and XANES revealed that doped Cr and Fe were present in the Cr3+ and Fe3+ states substituting for Ti sites in the La2Ti2O7 lattice. The theoretical calculation indicated that the most significant feature in the electronic band structure of the metal-doped La2Ti2O7 was the formation of a partially filled 3d band in the band gap of La2Ti2O7, while the contribution of these dopants on the valence band was negligible. Excitation of electrons from this localized interband to the conduction band of La2Ti2O7 was responsible for visible light absorption and the H2 evolution from water under visible light.
在寻找能在可见光下工作的高效光催化剂的过程中，我们研究了阳离子取代对层状钙钛矿La2Ti2O7的影响。在各种金属掺杂剂中，只有Cr和Fe能引起强烈的可见光吸收（λ>400 nm），并且只有这些催化剂在可见光照射（λ>420 nm）下，在甲醇存在的情况下能通过光催化从水中产生H2。结果发现，聚合络合法在制备本研究中的催化剂时比固态反应更有效，能产生更均匀的结构。通过XRD、UV-vis DRS、XPS和XANES进行的表征表明，掺杂的Cr和Fe以Cr3+和Fe3+的状态存在，取代了La2Ti2O7晶格中的Ti位点。理论计算表明，金属掺杂的La2Ti2O7电子能带结构中最显著的特征是在La2Ti2O7的带隙中形成了一个部分填充的3d带，而这些掺杂剂对价带的贡献可以忽略不计。电子从这个局域的带间激发到La2Ti2O7的导带，这是可见光吸收以及在可见光下从水中析出H2的原因。
