A Au/Cu2O-TiO2 system for photo-catalytic hydrogen production. A pn-junction effect or a simple case of in situ reduction?

作者：Sinatra L; LaGrow A P; Peng W; Kirmani A R; Amassian A; Idriss H^*; Bakr O M

来源：Journal of Catalysis, 2015, 322: 109-117.

DOI：10.1016/j.jcat.2014.11.012

• Hydrogen production
• pn-Junction
• XPS-Cu2p
• Energy band position
• Cu2O(111) Raman

Photo-catalytic H-2 production from water has been studied over Au-Cu2O nanoparticle deposited on TiO2 (anatase) in order to probe into both the plasmon resonance effect (Au nanoparticles) and the pn-junction at the Cu2O-TiO2 interface. The Au-Cu2O composite is in the form of similar to 10 nm Au nanoparticles grown on similar to 475 nm Cu2O octahedral nanocrystals with (I I 1) facets by partial galvanic replacement. X-ray Photoelectron Spectroscopy (XPS) Cu2p and Auger L3M4,5M4,5 lines indicate that the surface of Cu2O is mainly composed of Cu+. The rate for H-2 production (from 95 water/5 ethylene glycol; vol.%) over 2 wt.% (Au/Cu2O)-TiO2 is found to be similar to 10 times faster than that on 2 wt.% Au-TiO2 alone. Raman spectroscopy before and after reaction showed the disappearance of Cu+ lines (2E(u)) at 220 cm(-1). These observations coupled with the induction time observed for the reaction rate suggest that in situ reduction from Cu+ to Cu-0 occurs upon photo-excitation. The reduction requires the presence of TiO2 (electron transfer). The prolonged activity of the reaction (with no signs of deactivation) despite the reduction to Cu-0 indicates that the latter takes part in the reaction by providing additional sites for the reaction, most likely as recombination centers for hydrogen atoms to form molecular hydrogen. This phenomenon provides an additional route for enhancing the efficiency and lifetime of Cu2O-TiO2 photocatalytic systems, beyond the usually ascribed pn-junction effect.

• 出版日期2015-2