Bi/α-Bi2O3/TiO2 nanotubes heterojunction with enhanced UV and visible light activity: role of Bismuth

Scanning electron microscopy (SEM) and X-ray diffraction (XRD) characterizations were employed to evaluate the physico-chemical and surface characterization of the materials. Electrochemical impedance spectroscopy (EIS) was performed to evaluate the electronic properties and charge transport of the considered materials. The photoelectrochemical characterizations of the composite were carried out through linear sweep voltammetry (LSV). LSV and UV-Vis diffuse reflectance spectroscopy demonstrate that the incorporated Bi significantly enhances light absorption in the UV and visible spectral. Significant improvement in photocurrent density, up to 5 mA cm−2 at 1.5 V vs SCE, and a low onset potential, −0.4 V vs. SCE were found. The photoelectrochemical activity improvement can be attributed to enhanced absorption in the UV and visible light regions due to the presence of semimetallic Bi NPs with plasmon resonance (SPR) effect, more efficient charge separation/transportation due to the high specific surface area.