Abstract
Semiconductors mediated by rare earth metals (REMs) have attracted attention with regard to the degradation of pollutants. In order to enhance the visible response of TiO2, La-doped TiO2 (La-TO) photocatalysts with visible-light-driven capacity for NO removal were successfully synthesized in this study via a facile sol-gel method followed by calcination. A series of La-TiO2 samples with differing weight ratios were evaluated for their photocatalytic performances. It was found that 3% La integrated with TiO2 (in mass ratio) could enhance the removal efficiency of NO (up to 32%) under solar light, which is more than twice that seen with pure TiO2. The resulting products were characterized by a series of techniques, such as XRD, FTIR, UV-vis DRS, BET and (photo)electrochemical analysis. The results indicated that La-doped TiO2 can harvest visible light due to the relatively narrow band gap (from 2.98 to 2.75 eV). More importantly, La dopant improved electron-hole separation and suppressed charge carrier recombination, due to the synergistic effect. Furthermore, La-doped TiO2 increased the photo-oxidation efficiency of the transformation from NO to NO3–, owing to inhibition of the production of intermediate NO2 (0.02%). To the best of our knowledge, this study is the first time that La-doped TiO2 has been used to eliminate NO (at the ppb level) in the atmosphere. This study provides a facile and controllable route to fabricate La-TO photocatalyst for NO abatement with high selectivity of NO2 under visible light.
Highlights
NOx, which typically refers to NO and NO2, has been associated with Chinese haze and secondary organic aerosols (SOAs) in recent years (Huang et al, 2014; Shi et al, 2015; Fujitani et al, 2017)
In order to enhance the visible response of TiO2, La-doped TiO2 (La-TO) photocatalysts with visible-light-driven capacity for NO removal were successfully synthesized in this study via a facile sol-gel method followed by calcination
This means that pure anatase was synthesized at 500°C, and the degree of crystallinity degree of TiO2 was relatively poor at 400°C
Summary
NOx, which typically refers to NO and NO2, has been associated with Chinese haze and secondary organic aerosols (SOAs) in recent years (Huang et al, 2014; Shi et al, 2015; Fujitani et al, 2017). Titania has been explored for applications in many areas, such as photocatalysis, photovoltaics, water splitting (Chen and Mao, 2007; Thunyasirinon et al, 2015). Owing to such features as abundance, long-term stability against photochemical corrosion and being non-poisonous, huge efforts have been dedicated to utilizing TiO2 in photocatalysis (Devi and Kavitha, 2014; Yu et al, 2016). It is not feasible to use TiO2 to harvest visible light, because of the limitation of its bandgap (~3.0–3.2 eV). This means that TiO2 can only absorb UV light with a wavelength < 380 nm, and UV light accounts for a very small portion (5%) of solar light. Two key aspects of photocatalysis are the effective harvesting of solar
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