Investigation of the enhanced photocathodic activity of La5Ti2CuS5O7 photocathodes in H2 evolution by synchrotron radiation nanospectroscopy

Abstract

The local electronic structures of La₅Ti₂MS₅O₇ (M = Cu, Ag) particulate photoelectrodes with and without Ga doping were investigated, using a photoemission spectroscopy system with a lateral resolution of approximately 100 nm. The band alignments for La₅Ti₂MS₅O₇ were determined on the basis of pinpoint photoemission spectra acquired at optimal positions on the sample surfaces. A clear upward chemical potential shift of approximately 0.35 eV was observed in the case of Ga-doped La₅Ti₂CuS₅O₇. On the other hand, the electronic structure of La₅Ti₂AgS₅O₇ remained almost unaffected by Ga doping. These results explain the enhanced photocathodic response of La₅Ti₂CuS₅O₇ upon Ga doping.