Paper SS+EN-MoM1
Reaction Chemistry at Surfaces of Hematite-Based Photoelectrocatalysts

Monday, November 10, 2014, 8:20 am, Room 315

Hematite (α-Fe₂O₃)-based photoanodes are promising materials for photoelectrochemical hydrogen generation. We report on fundamental studies of surface structure and reaction chemistry associated with the heterogeneous oxidation of water on such materials by applying a classical surface science approach. We have characterized the structure and properties of Ni-doped and mixed-oxide hematite surfaces formed by vapor deposition under controlled conditions utilizing a range of techniques for surface analysis. The structure of Ni-modified thin films of α-Fe₂O₃ model catalysts with different morphology and geometry was characterized by LEED and STM. Then, water adsorption and reaction were studied by TPD, XPS, UPS, and vibrational spectroscopy by HREELS, characterizing the influence of Ni-modification on thermal and photochemical reaction mechanisms. Ni doping is found to be associated with a new termination for the α-Fe₂O₃(0001) film. Water TPD shows that Ni doping induces new surface chemistry, as revealed by a new, higher temperature OH recombination desorption peak, which is due to more stable surface-bound OH groups as identified by UPS. These surface-science type experiments were combined with photoelectrochemical water oxidation measurements on photoanodes prepared by thin-film and nano-materials synthesis to elucidate new information on the surface phases of hematite-based photoanodes and about their specific stability and reactivity toward photoelectrochemical water splitting.

This work was supported by the Addy/ISN North American Low Carbon Emission Energy Self-Sufficiency Fund of the Andlinger Center for Energy and the Environment (ACEE) and by the Grand Challenges Program at Princeton University.