Speaker: Freddy E. Oropeza (Postdoctoral Researcher of the Photoactivated Processes Unit)
Freddy E Oropeza is material scientist specialized in the analysis of surface chemistry and electronic structure of oxide semiconductors. His research interests focus on the investigation of the structure and electronic properties of functional metal oxide semiconductors with applications in catalysis, electronics and green energy technologies. His research approach is the experimental description of electronic basis that govern the functionality of catalytic and photovoltaic semiconductors. His research work has provided him with over 10 years of experience wet-chemistry thin film growth, advanced X-ray diffraction techniques, low-energy ion scattering (LEIS), photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS).
In the photoelectrochemical process, high-energy photogenerated charge carriers (electrons and holes) are transferred from a semiconductor photoabsorber (PA) to the reactant electrolyte. Usually, such transfer is assisted by a catalyst on the surface of the PA that promotes the chemical redox conversion associated to the charge transfer. It has been recognised that a valuable approach to promote an efficient charge transfer is the optimisation of energetics at surfaces and PA/catalyst interfaces by controlling parameters like band alignment between PA and catalysts, as well as surface/interface built-in potentials. Photoelectron spectroscopy (PES) effectively maps electronic levels of materials and it is sensitive to the surface potentials. Therefore, it is a powerful technique to explore and rationalise the functionality and efficiency of photoelectrodes. In this talk, I will present a PES study of built-in potential at the interface of Co3O4/SrTiO3 model samples and its beneficial impact on the charge mobility across the interface. I will also discuss how a Ni-induced hole state in Ni-doped Co3O4 anodes can further assists the charge transfer at the anode/electrolyte interface during the oxygen evolution reaction.
Freddy E. Oropeza
Auditorium, IMDEA Energy Institute