Using perovskite photocatalytic reduction of CO2 and H2O to produce hydrocarbon fuels offers an attractive method to solve the energy crisis and the greenhouse effect. Bi4Ti3O12 (BTO) has received much attention in the field of photocatalysis due to its unique layered structure, but it still faces many challenges such as weak photoresponse and severe photogenerated carrier recombination. In this paper, Bi4Ti3O12 nanosheets with different concentrations of surface oxygen vacancies (VO) and Ti3+ defect were prepared by the molten salt method and NaBH4 high-temperature reduction method (HBTO). Surface defects formed obvious carrier traps on the HBTO surface, reduced the recombination rate of photogenerated electrons and holes, and adjusted the band gap structure (from 3.09 to 2.62 eV), which improved the visible light utilization of HBTO. The decrease of photoinduced carrier recombination rate and the improvement of visible light response significantly enhanced the photocatalytic CO2 reduction activity of HBTO under visible light. The CH3OH yield with the optimized HBTO-4 (NaBH4:Bi4Ti3O12 = 1:5) was 4.90 μmol·g–1·h–1, which was about 3.5 times that of the original BTO. Meanwhile, the band gap structure, electronic density of states (DOS), and work function were calculated by the density functional theory (DFT). This study provided an effective strategy for designing and preparing perovskite photocatalysts rich in surface defects for the efficient conversion of solar energy.
Cocatalysts generally serve as active sites accelerating carrier separation. However, when the hydrophilicity of photocatalyst itself is poor, the trapped electrons or holes on cocatalysts are difficult to react with reactants quickly. In this work, Bi4Ti3O12 nanosheets with excellent hydrophilicity was prepared and then thermally deposited Rh on their surface (Bi4Ti3O12(Rh)), and finally in-suit grew ZnIn2S4 on the surface of Bi4Ti3O12(Rh). Based on the results of photocatalytic performance and materials characterization, it was found that the Bi4Ti3O12(Rh) in the photocatalytic system could be considered as a special cocatalyst rather than formed heterojunction with the ZnIn2S4. Under visible-light irradiation, the Rh acted as an electron trapping site to conduct photogenerated electrons trapping from ZnIn2S4 to the surface of Bi4Ti3O12. This process not only further accelerated carrier separation, but also facilitated electrons reacting with water due to the excellent hydrophilicity of Bi4Ti3O12(Rh), thereby achieving enhanced photocatalytic H2 production performance in the absence of sacrificial agents.
Yuting Qian,Wenrou Tian,Jun Han,Najun Li,Dongyun Chen,Qingfeng Xu,Hua Li,Jianmei Lu
Catalytic oxidation of HCHO is often limited by the serious recombination of carriers in photocatalysts and the high cost of thermal catalysts based on precious metals. Herein, Bi 4 Ti 3 O 12 nanosheets enriched with bismuth vacancies were synthesized and decorated by UiO-66-NH 2 to obtain VBiTO@NU-66 for efficient removal of HCHO via piezocatalytic oxidation. The Bismuth vacancies in VBiTO enhanced the asymmetry of the crystal structure and introduced the atomic-level channels for energy and electron transfer. After loading UiO-66-NH 2 , the adsorption ability was substantially improved by the formation of Schiff-base covalent bonds between HCHO and –NH 2 . Under the joint action of adsorption and piezocatalysis, piezocatalytic oxidation rate of 300 mg/m 3 HCHO by VBiTO@NU-66 was as high as 95.1% within 3 h, which was 6 times of that of pure BiTO nanosheets. This work offers a novel tactics for the efficient purification of gaseous environmental pollutants.
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