Crystal Facet Dependent Energy Band Structures of Polyhedral Cu 2 O Nanocrystals and Their Application in Solar Fuel Production.

We demonstrated a facile hydrothermal method to synthesize the (100)-, (110)- and (111)-oriented Cu 2 O nanocrystals (NCs) by controlling the concentration of the incorporated anions (CO 3 2- and SO 3 2- ). The crystal facet dependent activity of the orientation controlled Cu 2 O NCs in the rhodamine B (RhB) photodegradation and photocatalytic hydrogen (H 2 ) evolution was found to follow the trend: (111) > (110) > (100). The mechanism was investigated by characterizing the optical property, energy band structure, interfacial charge carrier dynamics and reducing ability. The results indicated that the (111)-oriented Cu 2 O NCs exhibit the higher conduction band (CB) potential as compared with the (110)-oriented and (100)-oriented Cu 2 O NCs, which resulted in the largest driving force of interfacial electron transfer for (111)-oriented Cu 2 O NCs to carry out solar fuel generation. The current study offers an easy strategy for crystal facet engineering of semiconductors and provides important physical insights into their electronic properties for the desired solar energy conversions.