煅烧结合光辐照提高纳米AgI/TiO2的可见光响应

为提高AgI/TiO₂的可见光响应能力，采用煅烧结合光辐照的工艺对其进行改性.紫外-可见光吸收分析表明，改性AgI/TiO₂的敏感光谱范围覆盖了整个可见区，吸收边带从465 nm红移至800 nm，在500 nm处的吸光度提高了近3倍.X-射线衍射分析结果指出，煅烧提高了金红石型TiO₂的相对含量，导致禁带宽度从2.89 eV降到2.81 eV，氙灯辐照进一步增加了锐钛型TiO₂、金红石型TiO₂和AgI的相对含量，并生成了新的晶体AgCl，使其禁带宽度又降至1.55 eV左右.AgCl的产生、AgI和金红石型TiO₂相对含量的增加是降低改性材料禁带宽度和增强可见光响应能力的主要原因.研究还表明，只有煅烧后的AgI/TiO₂才能通过光辐照来拓宽可见光敏感范围，而且，光辐照中起作用的主要是紫外光，可见光的作用甚小.研究最后提出将2种或2种以上的卤化银负载在纳米TiO₂上，更能有效地增强TiO₂的可见光响应能力.

Enhanced Visible-light Absorbance of Nanosized AgI/TiO2 by Using Calcination Combined with Light Irradiation

With the aim to enhance visible-light absorbance, calcination combined with light irradiation was used to modify nanosized AgI/TiO₂. UV-Vis spectrum curves indicated that the modified sample exhibited an intense absorption in the whole visible light range and a spectrum shifted from 465 nm to 800 nm, and that absorbance at 500 nm was improved three times as much as that of the reported pertinent material. XRD analytic results demonstrated that calcined AgI/TiO₂ possessed more rutile phase with reduced band gap from 2.89 eV to 2.81 eV, and that the following xenon-light irradiation further enhanced the relative contents of anatase TiO₂, rutile TiO₂ and AgI accompanied with produced AgCl phase, leading to the decrease in band gap to 1.55 eV. Formation of AgCl and increases in the relative contents of rutile TiO₂ and AgI should take the main responsibilities for the decrease in the band gap and enlargement of visible-light absorbance. Additionally, it was confirmed that only the spectrum absorption of the calcined AgI/TiO₂ could be improved by light irradiation, and that ultraviolet light played more role than visible part during the light irradiation. Moreover, it was proposed here that two or more silver halides supported on TiO₂ could show more capabilities to stimulate visible-light activation of TiO₂.