Journal Article Electronic structures and photoanodic properties of ilmenite-type MTiO<sub>3</sub> epitaxial films (M = Mn, Fe, Co, Ni)

吉松, 公平  ,  Yoshimatsu, Kohei  ,  増子, 尚徳  ,  Mashiko, Hisanori  ,  梅澤, 直人  ,  Umezawa, Naoto  ,  堀場, 弘司  ,  Horiba, Koji  ,  組頭, 広志  ,  Kumigashira, Hiroshi  ,  大友, 明  ,  Ohtomo, Akira

We performed systematic study on electronic structures and photoelectrochemical (PEC)properties of ilmenite-type MTiO3 (M = Mn, Fe, Co, and Ni) thin-film photoanodes for wateroxidation reactions. Single-phase MTiO3 films were grown on α-Al2O3 substrates by usingpulsed-laser deposition. Formation of the ilmenite-type structures and oxidation states ofM2+Ti4+O3 were revealed by X-ray diffraction and X-ray absorption spectroscopy, respectively.The PEC performance in water was investigated by linear sweep voltammetry under Xe-lampillumination and incident photon to conversion efficiency measurements under monochromaticillumination. We found that NiTiO3 acted as the most effective photoanode among MTiO3. Themechanism of the different PEC performance was discussed from the viewpoint of the electronicstructures investigated by photoemission spectroscopy and band calculation based on densityfunctional theory. We revealed that the stronger hybridization between O 2p and M 3d states wasresponsible for the more efficient photoanodic activity among ilmenite-type MTiO3.

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