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▲ [19p-C103-7] Determining the Rh dopant site structure in Rh:SrTiO3 photocatalysts
Keywords:photocatalyst, dopant site structure, x-ray fluorescence holography
Photoelectrochemical water splitting is a potentially attractive method for producing hydrogen from water with the help of sunlight. The process relies on a semiconductor photoelectrode that absorbs sunlight and injects either photoexcited electrons or holes into water, producing either hydrogen or oxygen. A p-type semiconductor, such as Rh-doped SrTiO3 can be used as a water-stable hydrogen evolution electrode material. Unfortunately, doped oxide semiconductors such as Rh:SrTiO3 exhibit exceedingly short, picosecond scale photocarrier lifetimes and mobilities that are far below the Hall mobility when the same material is doped to a metallic state, i.e., Nb:SrTiO3. The purpose of this work is to use X-ray fluorescence holography (XFH) to determine what types of dopant-related defect structures form in Rh:SrTiO3 and to develop doping schemes that may reduce carrier trapping and improve the energy conversion efficiency of a photoelectrode.
XFH measurements were performed on Rh4+:SrTiO3 and Rh3+:SrTiO3 thin film samples at SPring-8 BL13XU. Reconstructions of atomic positions around the Rh dopant site are shown for a Rh3+:SrTiO3 film in Fig. 1. The detected atomic positions were compared with possible defect cluster structures and two of the most likely defects types were identified: the formation of Rh-VO-Rh clusters, and metallic Ti-Rh-Ti clusters where the dopant atom occupies the oxygen site. The structural models for these defect clusters are shown in Fig. 1. This work shows that XFH is an effective tool for uniquely identifying dopant site structures in perovskites, providing useful information for designing electronically cleaner doping schemes and synthesis procedures.
XFH measurements were performed on Rh4+:SrTiO3 and Rh3+:SrTiO3 thin film samples at SPring-8 BL13XU. Reconstructions of atomic positions around the Rh dopant site are shown for a Rh3+:SrTiO3 film in Fig. 1. The detected atomic positions were compared with possible defect cluster structures and two of the most likely defects types were identified: the formation of Rh-VO-Rh clusters, and metallic Ti-Rh-Ti clusters where the dopant atom occupies the oxygen site. The structural models for these defect clusters are shown in Fig. 1. This work shows that XFH is an effective tool for uniquely identifying dopant site structures in perovskites, providing useful information for designing electronically cleaner doping schemes and synthesis procedures.