Coincorporation of N and\nTa into TiO₂ Nanowires\nfor Visible Light Driven Photoelectrochemical Water Oxidation

Abstract

We report a synthesis of N- and Ta-coincorporated TiO₂ (N,Ta:TiO₂) and Ta-incorporated TiO₂ (Ta:TiO₂) nanowire (NW) arrays and their application\nas photoanodes\nfor water photooxidation. Tantalum is incorporated into TiO₂ NWs with concentrations ranging from 0.11 to 3.47 atomic % by a\nsimple solvothermal synthesis. N,Ta:TiO₂ nanowires are\nprepared via nitridation of Ta:TiO₂ nanowires in NH₃ flow at a relatively low temperature (500 °C). N,Ta:TiO₂ NWs with the optimum Ta concentration of 0.29 atomic % also\ndemonstrate significant enhancement in photoelectrochemical performance\nwith the photocurrent reaching 0.52 and 0.18 mA/cm² under\nAM 1.5 G and visible light (>420 nm) illumination, compared with\n0.26\nand 0.13 mA/cm² for that of N:TiO₂ NWs, although\nthe active spectrum of the N,Ta:TiO₂ NW sample only extends\nto ∼520 nm (2.38 eV), compared to ∼540 nm (2.30 eV)\nfor N:TiO₂ NWs. We believe that the enhancement shown by\nthe N,Ta-coincorporated sample is due to fewer recombination centers\nfrom charge compensation effects and suppression of the formation\nof an amorphous layer on the nanowires during the nitridation process.