S1 Supplementary Information In-situ observation of carrier transfer in Mn-oxide/Nb:SrTiO 3 photoelectrode by X-ray absorption spectroscopy Masaaki Yoshida, *,a Takumi Yomogida, a Takehiro Mineo, a Kiyohumi Nitta, b Kazuo Kato, b Takuya Masuda, c Hiroaki Nitani, d Hitoshi Abe, d Satoru Takakusagi, e Tomoya Uruga, b Kiyotaka Asakura, e Kohei Uosaki, c,f,g and Hiroshi Kondoh, *,a a Department of Chemistry, Keio University, Yokohama, Japan b Japan Synchrotron Radiation Research Institute, Hyogo, Japan c Global Research Center for Environment and Energy based on Nanomaterials Science, National Institute for Materials Science (NIMS), Ibaraki, Japan d Institute of Materials Structure Science, KEK, Ibaraki, Japan e Catalysis Research Center, Hokkaido University, Sapporo, Japan, f International Center for Materials Nanoarchitechtonics (WPI-MANA), NIMS, Ibaraki, Japan g Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Japan *E-mail: yoshida@chem.keio.ac.jp; kondoh@chem.keio.ac.jp Index Page Experimental procedures S2 Schematic illustration of optical geometry for in situ XAFS measurements S5 Evolution of gases S6 In situ XAFS spectra at various potentials S7 Relation between Mn valence and absorption edge energy S9 Photocurrent monitored during in situ XAFS measurement S10 Time course of in situ XAFS spectra after changing potential S11 Difference between the thin film and particle samples S12 Reference S13 Electronic Supplementary Material (ESI) for Chemical Communications This journal is © The Royal Society of Chemistry 2013