Molybdenum-doped and anatase/rutile mixed-phase TiO2 nanotube photoelectrode for high photoelectrochemical performance

• Aligned TiO2 NTs with Mo-doping and mixed phase are achieved by one step hydrothermal process.
• Oxygen vacancies are increased and recombination of photo-excited charge is reduced.
• The photocurrent density is doubled.
• Mo-doped TiO2 NTs show visible-light absorption and high stability.

Molybdenum-doped TiO2 nanotube arrays (Mo-doped TiO2 NTs) photoelectrodes with anatase/rutile mixed phase are successfully fabricated via two-step anodization of titanium followed by a hydrothermal doping treatment process. The Mo-doped TiO2 NT material shows higher photocurrent density and enhanced incident photon to current conversion efficiency (IPCE) compared with the pristine TiO2 NTs for photoelectrochemical (PEC) water-splitting. The improvement of PEC response results from not only the increasing of oxygen vacancies and reducing of the recombination of photoexcited charges by Mo-doping, but also the new formed heterojunctions of anatase/rutile mixed-phase by hydrothermal treatment. Moreover, the Mo-doped TiO2 NTs show high stability and obvious visible absorption with considerable photocurrent density under visible light (λ > 420 nm).