Facile one-pot controlled synthesis of Sn and C codoped single crystal TiO2 nanowire arrays for highly efficient photoelectrochemical water splitting

• Sn and C codoped single crystal TiO2 nanowire array photoanode was prepared.
• Codoped photoanode showed superior photoelectrochemical water splitting activity.
• It generated 2.8 mA/cm2 photocurrent density and solar-to-fuel efficiency of 1.32%.
• Codoping increased the density, lifetime of charge carriers and the conductivity.
• Amount of Sn and C in the codoped system was higher than in each monodoped system.

Here we report a (Sn, C) cation–anion codoped single crystal TiO2 nanowire (NW) arrays as a highly efficient solar water splitting photoelectrode, able to be fabricated using a facile one pot hydrothermal synthesis method. The synergetic effects of codoping on the photoelectrochemical activity of the photoanode were investigated and compared to undoped and monodoped photoelectrodes. The (Sn, C) codoped TiO2 NW photoanode generated the highest saturated photocurrent density i.e. 2.8 mA/cm2 at 1.23 V vs RHE while yielding a maximum solar energy conversion efficiency of 1.32% at a potential of 0.55 V vs RHE – representing 60%, 94%, and 100% efficiency improvements compared to undoped, Sn doped, and C doped TiO2 NW respectively at same potential. This improvement is attributed to the synergetic effects of Sn and C codopants to lower recombination and enhance life time of photogenerated charge-separated carriers on the surface states that lead to efficient hole transfer at the photoelectrode/electrolyte interface. In addition, an increased charge carrier density and conductivity (as evidenced from electrochemical impedance spectroscopy) and the enhanced incorporation of dopants in the codoped system, compared to monodoped system as quantified by XPS, highlights the importance of codoping. The nanomaterial was characterized by XRD, TEM, SEM and Raman UV–vis measurements. This study will guide improvements in the efficiency of TiO2 for PEC water splitting using optimized codopant pairs.

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