高催化活性2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)纳米片异质结的构建及其可见光催化去除NO

2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)Nanosheet Heterojunction with Enhanced Visible Light Photocatalytic Activity for NO Removal

本研究采用水热法构建出2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)纳米异质结,在可见光下研究了该复合材料对NO的光催化去除能力。实验表明,15%Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)对NO的光催化去除效率相比纯Bi_(4)O_(5)Br_(2)显著提高:其降解效率达到57.6%,比Bi_(4)O_(5)Br_(2)高27.1%。同时,15%Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)具有很好的稳定性,经过5次循环催化,其催化率依然接近50.0%。研究发现,反应过程中主要的反应活性物质是e^(−)和·O_(2)^(−),光氧化产物主要为NO_(2)^(−)和NO_(3)^(−)。分析复合材料的光催化机制,发现光催化活性的提高主要得益于2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)异质结提高了电子与空穴的分离率,从而提高了光催化效率。这项工作提供了一个制备2D/2D纳米复合材料用于光催化降解环境污染物的有效方法,在缓解能源紧张与环境污染方面有巨大应用潜力。

This study concentrated on the production of a two-dimensional and two-dimensional(2D/2D)Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)heterojunction with a large interface that applied as one of the novel visible-light-induced photocatalyst via the hydrothermal method.The obtained photocatalysts enhanced the photocatalytic efficiency of the NO removal.The crystal structure and chemical state of the composites were characterized using X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The results showed that Ti_(3)C_(2),Bi_(4)O_(5)Br_(2),and Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)were successfully synthesized.The experimental results of scanning electron microscopy(SEM)and transmission electron microscopy(TEM)showed that the prepared samples had a 2D/2D nanosheet structure and large contact area.This structure facilitated the transfer of electrons and holes.The solar light absorptions of the samples were evaluated using the UV-Vis diffuse reflectance spectra(UV-Vis DRS).It was found that the absorption band of Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)was wider than that of Bi_(4)O_(5)Br_(2).This represents the electrons in the Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)nanosheet composites were more likely to be excited.The photocatalytic experiments showed that the 2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)composite with high photocatalytic activity and stability.The photocatalytic efficiency of pure Bi_(4)O_(5)Br_(2)for the NO removal was 30.5%,while for the 15%Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)it was 57.6%.Moreover,the catalytic reaction happened in a short period.The concentration of NO decreased exponentially in the first 5 min,which approximately reached the final value.Furthermore,the stability of 15%Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)was favorable:the catalytic rate was approximately 50.0%after five cycles of cyclic catalysis.Finally,the scavenger experiments,electron spin resonance spectroscopy(ESR),transient photocurrent response,and surface photovoltage spectrum(SPS)were applied to analyze the photocatalytic mechanism of the composite.The results indicated that the 2D/2D heterojunction Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)improved the separation rate of the electrons and holes,thus enhancing the photocatalytic efficiency.In the photocatalytic reactions,the photogenerated electrons(e^(−))and superoxide radical(·O_(2)^(−))were critical active groups that had a significant role in the oxidative removal of NO.The in situ Fourier-transform infrared spectroscopy(in situ FTIR)showed that the photo-oxidation products were mainly NO_(2)^(−)and NO_(3)^(−).Based on the above experimental results,a possible photocatalytic mechanism was proposed.The electrons in Bi_(4)O_(5)Br_(2)were excited by visible light.They jumped from the valence band(VB)of Bi_(4)O_(5)Br_(2)to the conduction band(CB).Then,the photoelectrons transferred from the CB of Bi_(4)O_(5)Br_(2)to the Ti_(3)C_(2)surface,which significantly promoted the separation of the electron-hole pairs.Therefore,the photocatalytic efficiency of Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)on NO was significantly improved.This study provided an effective method for preparing 2D/2D Ti_(3)C_(2)/Bi_(4)O_(5)Br_(2)nanocomposites for the photocatalytic degradation of environmental pollutants,which has great potential in solving energy stress and environmental pollution.