Time-resolved infrared spectroscopic investigation of Ga2O3 photocatalysts loaded with Cr2O3-Rh cocatalysts for photocatalytic water splitting

Abstract Investigation of the charge dynamics and roles of cocatalysts is crucial for understanding the reaction of photocatalytic water splitting on semiconductor photocatalysts. In this work, the dynamics of photogenerated electrons in Ga2O3 loaded with Cr2O3-Rh cocatalysts was studied using time-resolved mid-infrared spectroscopy. The structure of these Cr2O3-Rh cocatalysts was identified with high-resolution transmission electron microscopy and CO adsorption Fourier-transform infrared spectroscopy, as Rh particles partly covered with Cr2O3. The decay dynamics of photogenerated electrons reveals that only the electrons trapped by the Rh particles efficiently participate in the H2 evolution reaction. The loaded Cr2O3 promotes electron transfer from Ga2O3 to Rh, which accelerates the electron-consuming reaction for H2 evolution. Based on these observations, a photocatalytic water-splitting mechanism for Cr2O3-Rh/Ga2O3 photocatalysts has been proposed. The elucidation of the roles of the Cr2O3-Rh cocatalysts aids in further understanding the reaction mechanisms of photocatalytic water splitting and guiding the development of improved photocatalysts.