Centre for Research in Engineering Surface Technology (CREST), and School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin Street, Dublin 8, Ireland.
Inorg Chem. 2012 Jul 2;51(13):7164-73. doi: 10.1021/ic3001653. Epub 2012 Jun 12.
Highly visible-light-active S,N-codoped anatase-rutile heterojunctions are reported for the first time. The formation of heterojunctions at a relatively low temperature and visible-light activity are achieved through thiourea modification of the peroxo-titania complex. FT-IR spectroscopic studies indicated the formation of a Ti(4+)-thiourea complex upon reaction between peroxo-titania complex and thiourea. Decomposition of the Ti(4+)-thiourea complex and formation of visible-light-active S,N-codoped TiO(2) heterojunctions are confirmed using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and UV/vis spectroscopic studies. Existence of sulfur as sulfate ions (S(6+)) and nitrogen as lattice (N-Ti-N) and interstitial (Ti-N-O) species in heterojunctions are identified using X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopic techniques. UV-vis and valence band XPS studies of these S,N-codoped heterojunctions proved the fact that the formation of isolated S 3p, N 2p, and Π* N-O states between the valence and conduction bands are responsible for the visible-light absorption. Titanium dioxide obtained from the peroxo-titania complex exists as pure anatase up to a calcination temperature as high as 900 °C. Whereas, thiourea-modified samples are converted to S,N-codoped anatase-rutile heterojunctions at a temperature as low as 500 °C. The most active S,N-codoped heterojunction 0.2 TU-TiO(2) calcined at 600 °C exhibits a 2-fold and 8-fold increase in visible-light photocatalytic activities in contrast to the control sample and the commercial photocatalyst Degussa P-25, respectively. It is proposed that the efficient electron-hole separation due to anatase to rutile electron transfer is responsible for the superior visible-light-induced photocatalytic activities of S,N-codoped heterojunctions.
首次报道了具有高光活性的 S、N 共掺杂锐钛矿-金红石异质结。通过过氧钛络合物的硫脲修饰，在相对较低的温度下实现了异质结的形成和可见光活性。FT-IR 光谱研究表明，过氧钛络合物与硫脲反应后形成 Ti(4+)-硫脲络合物。X 射线衍射、拉曼光谱、透射电子显微镜和紫外可见光谱研究证实了 Ti(4+)-硫脲络合物的分解和可见光活性 S、N 共掺杂 TiO(2)异质结的形成。X 射线光电子能谱（XPS）和 FT-IR 光谱技术证实了异质结中硫以硫酸盐离子（S(6+））和氮以晶格（N-Ti-N）和间隙（Ti-N-O）形式存在。这些 S、N 共掺杂异质结的紫外可见和价带 XPS 研究证明，价带和导带之间形成孤立的 S 3p、N 2p 和 Π* N-O 态是可见光吸收的原因。由过氧钛络合物得到的二氧化钛在高达 900°C 的煅烧温度下以纯锐钛矿形式存在。然而，硫脲改性样品在低至 500°C 的温度下转化为 S、N 共掺杂锐钛矿-金红石异质结。在 600°C 下煅烧的最活跃的 S、N 共掺杂异质结 0.2 TU-TiO(2)，与对照样品和商业光催化剂 Degussa P-25 相比，可见光光催化活性分别提高了 2 倍和 8 倍。据推测，由于锐钛矿向金红石的电子转移，高效的电子-空穴分离是 S、N 共掺杂异质结具有优异的可见光诱导光催化活性的原因。
