Photoreduction Kinetics of Sodium Tetrachloroaurate under Synchrotron Soft X-ray Exposure

We report on the time evolution of the sodium tetrachloroaurate (NaAuCl4) chemical properties as a function of soft X-ray exposure in a dried sample on a silicon surface using X-ray photoelectron spectroscopy (XPS). Our investigations provide mechanistic insight into the photoreduction kinetics from Au-III to Au-I and then Au-I to Au-o. We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au-I state. Both photoreduction steps undergo first-order kinetics.