PHOTOCATALYTIC PRODUCTION OF H2O2 AND ORGANIC PEROXIDES ON QUANTUM-SIZED SEMICONDUCTOR COLLOIDS
PHOTOCATALYTIC PRODUCTION OF H2O2 AND ORGANIC PEROXIDES ON QUANTUM-SIZED SEMICONDUCTOR COLLOIDS
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DOI：
10.1021/es00054a006
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发表时间：
1994-05-01
影响因子：
11.4
通讯作者：
HOFFMANN, MR
中科院分区：
文献类型：
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作者：
HOFFMAN, AJ;CARRAWAY, ER;HOFFMANN, MR
在光照(320小于或等于波长小于或等于370 nm)下，透明量子尺寸(Q尺寸)的氧化锌半导体胶体在羧酸和氧气存在下的水悬浮液显示出产生高达2 mm的H_2O_2的稳定浓度。只有在添加电子给体(即空穴清除剂)的情况下，才能观察到最大的过氧化氢浓度。清孔剂的效率大小顺序为：甲酸盐+GT>草酸盐+GT>醋酸盐+GT>柠檬酸盐。O-18(2)的同位素标记实验与过氧化氢是通过导带电子还原吸附的氧直接产生的假设一致。在低光子通量下，H_2O_2的量子产率接近30%。然而，量子产率与吸收光强的平方根倒数[PHi与(i(Abs)-1)1/2]成正比，与激发波长和Q尺寸胶体的直径成正比。Q尺寸的氧化锌颗粒(D(P)=4-5 nm)比块体尺寸的氧化锌颗粒(D(P)=0.1um)产生H_2O_2的初始速率快100-1000倍。
Illuminated (320 less-than-or-equal-to lambda less-than-or-equal-to 370 nm), aqueous suspensions of transparent quantum-sized (Q-sized) ZnO semiconductor colloids in the presence of carboxylic acids and oxygen are shown to produce steady-state concentrations of H2O2 as high as 2 mM. Maximum H2O2 concentrations are observed only with added electron donors (i.e., hole scavengers). The order of efficiency of hole scavengers is as follows: formate > oxalate > acetate > citrate. Isotopic labeling experiments with O-18(2) are consistent with the hypothesis that hydrogen peroxide is produced directly by the reduction of adsorbed oxygen by conduction band electrons. Quantum yields for H2O2 production are near 30 % at low photon fluxes. However, the quantum yield is shown to vary with the inverse square root of absorbed light intensity [PHI is-proportional-to ((I(abs))-1)1/2], with the wavelength of excitation, and with the diameter of the Q-sized colloids. The initial rate of H2O2 production is 100-1000 times faster with Q-sized ZnO particles (D(p) = 4-5 nm) than with bulk-sized ZnO particles (D(p) = 0.1 mum).