Details

Autor(en) / Beteiligte

• Pinaud, Blaise A
• Chen, Zhebo
• Abram, David N
• Jaramillo, Thomas F

Titel

Thin Films of Sodium Birnessite-Type MnO2: Optical Properties, Electronic Band Structure, and Solar Photoelectrochemistry

Ist Teil von

• Journal of physical chemistry. C, 2011-06, Vol.115 (23), p.11830-11838

Ort / Verlag

American Chemical Society

Erscheinungsjahr

2011

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Inexpensive and earth-abundant, manganese oxides (Mn x O y ) have attracted considerable attention for catalysis, but fewer efforts have focused on their semiconducting properties. In this study, crystalline Na birnessite-type MnO2 thin films were investigated for their surface and bulk chemistry in the context of hydrogen production by photoelectrochemical water splitting. Thin films were synthesized by electrodeposition onto fluorine-doped tin oxide (FTO) substrates, imaged by scanning electron microscopy (SEM), and characterized by X-ray diffraction (XRD) as well as X-ray photoelectron spectroscopy (XPS) and UV–vis spectroscopy. Three different electrochemical methods (illuminated open circuit potential, potential of photocurrent onset, and Mott–Schottky plots) were used to probe the flat-band potential required to construct a band diagram for the material. Photostability, conductivity, and band structure are discussed as potential causes of the low external quantum efficiency (<1%) for the birnessite-type MnO2 photoanode. The position of the conduction band well below the hydrogen evolution potential likely mitigates this material’s potential use in a single absorber configuration, but its chemical, optical, and electronic characteristics as shown in this work may be well-suited for a photoanode in a tandem device.