Electronic Structure and Photoelectrochemical Properties of an Ir-Doped SrTiO3 Photocatalyst
journal contributionposted on 04.09.2014, 00:00 by Seiji Kawasaki, Ryota Takahashi, Kazuto Akagi, Jun Yoshinobu, Fumio Komori, Koji Horiba, Hiroshi Kumigashira, Katsuya Iwashina, Akihiko Kudo, Mikk Lippmaa
The effect of iridium valence in Ir:SrTiO3 on the electronic structure and the photocatalytic activity in a water splitting reaction was studied. Epitaxial thin film photoelectrodes were grown with controlled Ir valence and used to measure the electrochemical efficiency of Ir:SrTiO3. The positions of the in-gap Ir impurity levels were determined by optical and X-ray photoelectron spectroscopies. Comparison with ab initio calculations was used to assign the observed electronic states to either Ir4+ or Ir3+ dopants in SrTiO3. The measurements show that Ir3+:SrTiO3 forms a single midgap impurity state that is strongly localized, completely quenching the photoelectrochemical response. An anodic photoresponse was seen in Ir4+:SrTiO3 under visible-light illumination up to a wavelength of 600 nm (hν = 2.0 eV). Ir4+:SrTiO3 contains an in-gap state close to the top of the SrTiO3 valence band. The performance of Ir4+:SrTiO3 in electrochemical reactions is compared with cathodic Rh3+:SrTiO3, clearly illustrating the importance of strong dopant d-electron hybridization with the oxygen 2p valence band of SrTiO3 for improving the energy conversion efficiency in SrTiO3-based photocatalysts.
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600 nmenergy conversion efficiencyiridium valenceSrTiO 3 valence bandphotoelectrochemical responsemeasurements showanodic photoresponsefilm photoelectrodeswater splitting reactionSrTiO 3.h νoxygen 2 p valence bandelectrochemical efficiencyIr valence2.0 eVmidgap impurity statePhotoelectrochemical Propertiesab initio calculationsElectronic Structureelectrochemical reactionsSrTiO 3photocatalytic activity