Cu2O/Cu/TiO2 nanotube Ohmic heterojunction arrays with enhanced photocatalytic hydrogen production activity

Cu2O/Cu/TiO2 nanotube heterojunction arrays were prepared by assembling Cu@Cu2O core-shell nanoparticles on TiO2 nanotube arrays (NTAs) using a facile impregnation-reduction method. SEM and TEM results show that Cu@Cu2O plate-like nanoparticles with tens of nanometers in size are confined inside TiO2 NTAs. Only the outmost several nanometers of the nanoparticles are Cu2O and the predominant inner of the nanoparticles are Cu metals. Cu L3VV Auger spectra of Cu2O/Cu/TiO2 NTAs suggest that Cu metals are enveloped by at least several nanometers Cu2O on the surface, which further confirms the Cu@Cu2O core shell structure of Cu nanoparticles. The ability of light absorption of Cu2O/Cu/TiO2 NTAs is enhanced. The range of absorption wavelengths changes from 400 to 700 nm due to the surface plasmon response of Cu metals core and Cu2O nanoparticles shell. The photocatalytic hydrogen production rate of Cu2O/Cu/TiO2 heterojunction arrays is enhanced when compared with those of Cu2O/TiO2 NTAs and TiO2 NTAs under UV light. Moreover, a stable H2 generation property was obtained under visible light (λ gt; 400 nm). The Cu metal core is believed to play a key role in the enhancement of photocatalytic properties of Cu2O/Cu/TiO2 nanotube heterojunction arrays.