Effects of Substitutional Dopants on the Photoresponse of a Polyoxotitanate Cluster

Junyi Hu, Lijie Zhan, Guanyun Zhang, Qun Zhang, Lin Du, Chen Ho Tung, Yifeng Wang

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

In this paper, using a simple method, 17 isostructural polyoxotitanates (POTs) were synthesized, including the pristine [Ti12O16(OiPr)16], the monodefected [Ti11O13(OiPr)18], and the heterometal-doped [Ti11O14(OiPr)17(ML)] (M = Mg, Ca, Zn, Cd, Co, or Ni; L = Cl, Br, I, or NO3). The electronic structures of these POTs were determined by UV-vis spectroscopy and DFT calculations. Upon UV irradiation of the POTs, electron spin resonance showed the formation of TiIII under anaerobic conditions and superoxide (O2•-) in the presence of O2. The photoactivities of the POTs were then probed with TiIII production and short-circuit photocurrent experiments. The photophysical processes were studied using steady-state and transient photoluminescence. The results show that within the very similar structures, the deexcitation processes of the photoexcited POTs can be greatly affected by the dopants, which result in enhanced or decreased photoactivities. Co and Ni doping enhances the absorption of the visible light accompanied by serious loss of UV photoactivities. On the other hand, a Ti vacancy (in [Ti11O13(OiPr)18]) does not reduce the band gap of a POT but improves the UV photoactivities by serving as surface reaction site. The POTs were then used as molecular models of titanium oxide nanoparticles to understand some important issues relevant to doped titanate, i.e., coordination environment of the dopant metal, electronic structure, photoactivities, and photophysical processes. Our present findings suggest that for solar energy harvesting applications of titanium oxides like photocatalysis and solar cells substitution of titanium atoms by transition metal ions (like Co and Ni) to extend the absorption edges may not be an efficient way, while loading of Ti vacancies is very effective.

Original languageEnglish
Pages (from-to)8493-8501
Number of pages9
JournalInorganic Chemistry
Volume55
Issue number17
DOIs
StatePublished - 6 Sep 2016
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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