摘要
在波长λ≥320nm的紫外灯照射下,水溶液中的银离子能在氧化铁和羟基氧化铁催化剂表面发生还原反应而生成颗粒银.在这些催化剂上,Ag(I)的等温吸附线都符合Langmuir吸附方程;Ag(I)的初始还原速率均随其初始吸附量的增加而线性增大,并且增大的幅度依α-Fe2O3>α-FeOOH>γ-Fe2O3>γ-FeOOH>δ-FeOOH的顺序降低.但是,在前三种催化剂上,只有当Ag(I)的吸附量达到其饱和吸附量的一半时,Ag(I)的还原才能发生,并且几乎不受氮气的影响.在δ-FeOOH和TiO2体系中通入氮气,能显著加快Ag(I)的光催化还原.这说明O2与Ag(I)竞争催化剂上的吸附位点和还原物种,且与催化剂的性质有关.XRD分析表明,α-Fe2O3和δ-FeOOH分别具有较好和较差的结晶度.这说明氧化铁和羟基氧化铁的结晶度越高,越有利于光生载流子的分离及其与表面目标物种发生氧化还原反应.
Irradiation of an aerated aqueous suspension of silver nitrate and catalysts （ferric oxides and ferric hydroxides） with UV light （wavelength A ≥320 nm） led to the production of fine silver particles. On these catalysts, all the adsorption isotherms of silver ions fitted well to the Langmuir adsorption equation and the initial rate of Ag（I） reduction increased linearly with the increase in the initial amount of adsorbed Ag（I）. The slope decreased according to the following order： α-Fe2O3〉α-FeOOH〉γ-Fe2O3〉γ-FeOOH〉δ-FeOOH. However, for the first three catalysts the reduction of Ag（I） only occurred when the amount of adsorbed Ag（I） reached about half the maximum coverage and also the reaction rate was nearly unaffected by 5/2 purging. The reduction of Ag（I） on δ-FeOOH and TiO2 upon degassing with N2 was significantly accelerated. This implies that O2 competes with silver ions for adsorption sites and reducing species on the catalyst, which is dependent on the catalyst＇s properties. X-ray diffraction （XRD） analysis showed that α-Fe203 and 8-FeOOH were well and poorly crystallized, respectively. This indicates that the high crystallinity of the hydroxides is beneficial to the separation of photogenerated charge carriers and thus to their redox reactions with target substrates on the surface.
出处
《物理化学学报》
SCIE
CAS
CSCD
北大核心
2009年第8期1530-1534,共5页
Acta Physico-Chimica Sinica
基金
国家自然科学基金(20525724
20873124
J0830413)资助项目~~
关键词
光催化
氧化铁
羟基氧化铁
二氧化钛
银离子
光还原
Photocatalysis
Ferric oxide
Ferric hydroxide
Titanium dioxide
Silver ion
Photoreduction
