Electronic Structure and Photoelectrochemical Properties of an Ir-Doped SrTiO₃ Photocatalyst

Abstract

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.

Z-scheme photocatalyst systems employing Rh- and Ir-doped metal oxide materials for water splitting under visible light irradiation

“…In general, trivalent and tetravalent Rh and Ir species are doped at the Ti 4+ , Nb 5+ and Ta 5+ sites in metal oxide materials. [20][21][22][23][24][25]37,38 Among the species, Rh 3+ and Ir 3+ contribute to the visible light response for metal oxide photocatalysts. 20,24,37,38 Sb 5+ was codoped with Rh 3+ at the Ti 4+ and Nb 5+ sites for charge compensation to enhance the formation of Rh 3+ and Ir 3+ and suppress the formation of Rh 4+ and Ir 4+ as efficient recombination centers between photogenerated electrons and holes, while Ba 2+ and La 3+ were replaced at the alkali and alkaline earth metal sites for the same purpose.…”

Hybrid Density Functional Study on Mono‐ and Codoped NaNbO3 for Visible‐Light Photocatalysis

“…To improve the photocatalytic efficiency, the band gap of NaNbO 3 has to be reduced with respect to the HEP and OEP. Doping a semiconductor with metals or nonmetals is one of the most effective strategies to adjust its band structure to expand the range of optical adsorption towards the visible‐light region. Choo and Paul prepared a framework composition of Ru‐doped NaNbO 3 , which had an optical band gap of 2.3 eV and showed superior visible photocatalytic performance .…”

“…[24][25][26][27] Although several previous studies indicated that cubic NaNbO 3 with al ayered perovskite structure exhibited highera ctivity in photocatalytic H 2 generation than the other phases, [28][29][30][31][32][33][34] the wide band gap for cubic NaNbO 3 of 3.29 eV [32] limits the photocatalytic efficiencyi nt he visible-light region. To improvet he photocatalytic efficiency,t he band gap of NaNbO 3 has to be reduced with respect to the HEP and OEP.D oping as emiconductor with metals [35][36][37][38][39] or nonmetals [40][41][42][43] is one of the most effective strategies to adjust its band structure to expand the range of optical adsorption towards the visible-light region. Choo and Paul prepared aframework composition of Ru-doped NaNbO 3 ,w hich had an optical band gap of 2.3 eV and showed superior visible photocatalytic performance.…”

Electronic Structures and Photocatalytic Responses of SrTiO3(100) Surface Interfaced with Graphene, Reduced Graphene Oxide, and Graphane: Surface Termination Effect

“…9 Several strategies have been proposed to extend its optical absorption edge to the visible (vis) light region, which possesses 43% of the solar energy, through modifying the energy band structure of STO. Doping with foreign atoms, [10][11][12][13][14][15][16][17][18] depositing noble metal, 19 integrating with other materials [20][21][22][23] have been demonstrated to be effective methods to enhance the photocatalytic performance of STO. In the photocatalytic process, the charge carrier recombination occurs within nanoseconds.…”