Highly ordered TiO2 nanotube arrays wrapped with g-C3N4 nanoparticles for efficient charge separation and increased photoelectrocatalytic degradation of phenol.

Novel graphitic carbon nitride nanoparticles (NPs)-wrapped TiO2 nanotube arrays (NTAs) (g-C3N4/TiO2) were fabricated by a two-step method including an electrochemical anodization technique followed by impregnation under vacuum using urea as precursor. The as-prepared photoelectrode exhibited outstanding photoelectric properties and excellent photelectrocatalytic (PEC) performance for the degradation of phenol under stimulated solar light, which was due to the enhanced light absorption property and improved charge separation efficiency. The introduction of g-C3N4 NPs strongly decreased the charge transfer resistance and boosted the charge separation efficiency of TiO2. The optimum ratio of the g-C3N4/TiO2 yielded a pronounced 4.18-fold higher photocurrent density than TiO2. Besides, the combination of g-C3N4 NPs could negatively shift for the flat band potential of TiO2, resulting in an enhanced reduction property for the photoelectrocatalytic degradation of organic pollutants. The PEC process for the degradation of phenol over g-C3N4/TiO2 was much higher than the sum of photocatalytic (PC) and electrocatalytic (EC) processes indicating that a photoelectric synergy was achieved on the as-prepared photoelectrode and resulting in an improved PEC performance for the composite photoelectrode.