The efficient separation and HDAC activity assay transfer of election-hole pairs might also be associated with the interaction of V4+ and V5+. The V5+ species reacted with the electrons to yield V4+ species,

which on surface oxygen molecules generated the oxidant superoxide radical ion O2 −. O2 − reacted with H+ to produce hydroxyl radical and H+ and CO2 trapped electrons to produce •H and •CO2 −, which further reacted with holes to yield the final product, methane [34]. Superabundant V and N could result in a decrease of photoreduction activity for increasing recombination centers of electrons and holes. Conclusions V-N co-doped TiO2 nanotube arrays have been fabricated by a simple two-step method. V and N co-doped TiO2 photocatalysts exhibit fine this website tubular structures after hydrothermal click here co-doping process. XPS data reveal that N is found in the forms of Ti-N-O and V incorporates into the TiO2 lattice in V-N co-doped TNAs. V and N co-doping result in remarkably enhanced activity for CO2 photoreduction to CH4 due to the effective separation of electron-hole pairs. Meanwhile, the unique structure of co-doped TiO2 nanotube arrays promoted the electron transfer and the substance diffusion. Acknowledgements The authors thank the National Natural Science Foundation of China (no.21203054) and Program for Changjiang

Scholars and Innovation Research Team in University (no. PCS IRT1126). References 1. Mao J, Li K, Peng T: Recent advances in the photocatalytic CO 2 reduction over semiconductors. Catal Sci Technol 2013, 3:2481.CrossRef 2. Fujishima A, Zhang X, Tryk D: TiO 2 photocatalysis and related surface phenomena. Surf Sci Rep 2008, 63:515–582.CrossRef 3. Li Y, Wang W-N, Zhan Z, Woo M-H, Wu C-Y, Biswas P: Photocatalytic reduction of CO 2 with H 2 O on mesoporous silica supported Cu/TiO 2 catalysts. Appl Catal B Environ 2010, 100:386–392.CrossRef 4. Zhao C, Liu L, Zhang Q, Wang J, Li Y: Photocatalytic conversion of CO 2 and H 2 O to fuels by nanostructured Ce–TiO 2 /SBA-15 composites. Catal Sci Technol 2012, 2:2558.CrossRef 5. Zhang Q, Li Y, Tenoxicam Ackerman EA, Gajdardziska-Josifovska

M, Li H: Visible light responsive iodine-doped TiO 2 for photocatalytic reduction of CO 2 to fuels. Appl Catal A Gen 2011, 400:195–202.CrossRef 6. Li X, Zhuang Z, Li W, Pan H: Photocatalytic reduction of CO 2 over noble metal-loaded and nitrogen-doped mesoporous TiO 2 . Appl Catal A Gen 2012, 429–430:31–38.CrossRef 7. Zhao Z, Li Z, Zou Z: First-principles calculations on electronic structures of N/V-doped and N-V-dodoped anatase TiO 2 (101) surfaces. Chemphyschem Eur J chem Physics Physical chem 2012, 13:3836–3847.CrossRef 8. Gu D-E, Yang B-C, Hu Y-D: V and N co-doped nanocrystal anatase TiO 2 photocatalysts with enhanced photocatalytic activity under visible light irradiation. Catal Commun 2008, 9:1472–1476.CrossRef 9.