One-step hydrothermal synthesis of C-N-S-tridoped TiO2-based nanosheets photoelectrode for enhanced photoelectrocatalytic performance and mechanism

Abstract

C-N-S-tridoped TiO2-based nanosheets(BNSs) photoelectrode was prepared via a one-step hydrothermal strategy of the Ti plate in mixed solution of NaOH and cystine, followed by acid-washing and calcination. The resulting samples were characterized by X-ray photoelectron spectroscopy (XPS), scanning electrons microscopy (SEM), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectra (DRS). XPS analysis indicated that C, N and S were transferred into the lattice of TiO2. Highly ordered TiO2-BNSs with the sheet lengths of 500–1500nm and thickness of about 30nm were observed. XRD patterns showed that TiO2-BNSs before and after C, N and S tridoping were biphase of anatase-rutile. And tridoping with C, N and S could promote the phase transition from anatase to rutile and restrain growth of rutile crystallites. In addition, a shift of the absorption edge towards low energy and the intense visible light absorption were achieved. Photoelectrochemical (PECH) properties of the C-N-S-tridoped TiO2-BNSs photoanode were investigated through transient photocurrent response (TPR), open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The photoelectrocatalytic(PEC) performances were evaluated by the yield of •OH radicals and degradation of methyl orange(MO) under Xenon lamp irradiation. The results showed that C-N-S-tridoped TiO2-BNSs photoelectrode revealed high photogenerated current of 0.69mAcm−2, open-circuit photovoltage of -0.66mVcm−2, generation of •OH radicals and PEC efficiency of 96.8% for the degrading MO. Moreover, the enhanced PEC mechanism was proposed. The high PEC performance could be ascribed to the tridoping with C, N and S, which could not only improve the light harvesting in visible region but also enhance the mobility and separation efficiency of photogenerated charge carriers.