Photoinduced K+ Intercalation into MoO3/FTO Photoanode—the Impact on the Photoelectrochemical Performance

Abstract

Abstract In this work, thin layers of MoO 3 were tested as potential photoanodes for water splitting. The influence of photointercalation of alkali metal cation (K + ) into the MoO 3 structure on the photoelectrochemical properties of the molybdenum trioxide films was investigated for the first time. MoO 3 thin films were synthesized via thermal annealing of thin, metallic Mo films deposited onto the FTO substrate using a magnetron sputtering system. The Tauc and Mott–Schottky plots analysis were performed in order to determine the energy bands position of the investigated material. The photointercalation effect of K + on photoelectrochemical properties of FTO/MoO 3 photoanodes was studied using electrochemical techniques performed under simulated solar light illumination. It was proven that pristine MoO 3 layers cannot act as effective photoanodes for water splitting due to the utilization of the photoexcited electrons in the intercalation process. The photochromic phenomenon related to Mo 6+ centers reduction, and K + intercalation occurs at a potential range in which the photoanode exhibits photoelectrochemical activity towards water photooxidation.