Cathodic shift of onset potential on TiO₂ nanorod arrays with significantly enhanced visible light photoactivity via nitrogen/cobalt co-implantation

Despite anionic doping has been widely implemented to increase the visible light activity of TiO_2, it often gives rise to a dramatical anodic shift in current onset potential. Herein, we show an effective method to achieve the huge cathodic shift of TiO_2 photoanode with significantly enhanced visible light photo-electrochemical activity by nitrogen/cobalt co-implantation. The nitrogen/cobalt co-doped TiO_2 nanorod arrays (N/Co-TiO_2) exhibit a cathodic shift of 350 mV in onset potential relative to only nitrogen-doped TiO_2 (N-TiO_2). Moreover, the visible-light (\lambda >420 nm) photocurrent density of N/Co-TiO_2 reaches 0.46 mA/cm^2, far exceeding 0.07 mA/cm^2 in N-TiO_2 at 1.23 V versus reversible hydrogen electrode (RHE). Systematic characterization studies demonstrate that the enhanced photo-electrochemical performance can be attributed to the surface synergic sputtering of high-energy nitrogen/cobalt ions.