Simultaneous XAS measurement methods for solid‒liquid interfaces and bulk liquids were developed. In the liquid H2O layer on the Au thin films, the O K-edge XAS spectrum of bulk H2O was obtained using the transmission method, whereas the XAS spectrum of the H2O/Au interface was obtained using the electron-yield method. The simultaneous XAS measurement methods for solid‒liquid interfaces and bulk liquids are applicable for investigating the mechanisms of various catalytic, electrochemical, and biological reactions involving solid‒liquid interfaces.
