Effect of sodium carbonate as an additive on the morphology and photocatalytic activity of TiO2 nanotubes

•Sodium Carbonate as an additive led to dope Sodium and Carbon doped TiO2 nanotube arrays.•In doped nanotubes the band gap energy reduced from 3.2 to 2.88 ev.•In doped nanotubes the adsorption edge increased to about 92 nm longer wavelength.•The photocurrent density in doped nanotubes was about 5 times higher than in the pure ones.

The major purpose of this research is increasing the photocatalytic activity of TiO2 nanotube arrays by doping with sodium and carbon for using in water splitting as photoanode. The synthesized TiO2 nanotubes (TNA) were characterized using FESEM (Field Emission Scanning Electron Microscope), XRD (X-ray Diffraction), DRS (Diffraction Reflection Spectroscopy) and XPS test (X-ray Photoelectron Spectroscopy) analyses. The results of FTIR and XPS confirmed the presence of sodium and carbon in the lattice of TNA as dopants. Moreover, the DRS test showed the decrease in the band gap energy of TNA from 3.20 to ∼2.88 eV; uv-visible test exhibited extension in the absorption edge of pure TiO2 nanotubes from Uv-light (396 nm) to visible light (488 nm). In addition, the results of photoelectrochemical measurement indicated that the photocurrent density of doped TiO2 nanotubes increased about 5 times than that of the pure compounds.

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