Abstract:

Formaldehyde is a typical volatile organic compound(s) (VOCs) of indoor air pollutants. Surface plasmonic resonance (SPR) photocatalysts can absorb visible light,which allows solar light driven photocatalytic removal of formaldehyde from air to occur at room temperature and ambient pressure. However,very few studies on Au/TiO₂ photocatalyst of SPR for removal of formaldehyde from air are reported,of which the apparent kinetic study is of significance for the design of SPR catalysts and the applications to removal of VOCs pollutants. This paper studies the kinetics of photocatalytic oxidation of formaldehyde over plasmonic Au/TiO₂ under LED visible light. Effects of visible light sources with various wavelengths,light intensity and relative humidity of reaction gas on kinetics of visible-light photocatalytic oxidation of formaldehyde over Au/TiO₂ are investigated. Based on the experimental analyses,the apparent kinetics constant of k(I,H) for the LED visible light driven photocatalytic oxidation of formaldehyde is achieved. It suggests that,under conditions of 13% relative humidity and 38.5 mW·cm^-2 of blue light intensity,the formaldehyde conversion is 77%,almost 5 times that under dark. Under LED irradiations of red,green,blue and white light,the conversions of formaldehyde increases rapidly,slowly,and keeps steady with light intensity. Under the same conditons of light intensity (less than 42 mW·cm^-2) and relative humidity,the conversions of formaldehyde under LED red,green and blue light,are approximate,and the conversion under white light is relatively lower than that of the rest three. At dry condition,the converion of formaldehyde is almost 0. However,at wet condition,the conversions under light or under dark exist (above zero),and that under light is higher than under dark. The conversion as a function of relative humidity behaves similarily under various light sources. The conversion reaches the maximum at 21.9% of relative humidity,followed by almost being steady at 80%. Apparent kinetic parameters k(I)_H,k(H)_I and k(I,H) and the kinetic equations by fitting above data related to red,green,blue and whilte light are achieved and established.

Key words: Au/TiO₂, formaldehyde, photocatalysis, visible light, kinetics, LED, photochemistry, numerical analysis

摘要：

甲醛是室内空气中典型的挥发性有机化合物（VOCs）之一。等离子激元型光催化剂可吸收可见光，可在室温常压下利用太阳光驱动光催化氧化脱除室内空气中甲醛的反应，其表观反应动力学研究对设计等离子激元型光催化剂及应用于脱除VOCs等污染物具有重要意义。研究了LED可见光下等离子激元型Au/TiO₂光催化脱除气相中甲醛的表观反应动力学，考察不同波长的可见光源、光强及反应气相对湿度对表观反应动力学的影响，根据对实验数据的分析求得LED可见光催化氧化甲醛表观反应速率常数k（I，H）。结果表明，在13%相对湿度、蓝光光强为38.5 mW·cm^-2的条件下，光反应的甲醛转化率达77%，是暗反应的近5倍。在LED红、绿、蓝、白光照射下，随着光强增加，甲醛转化率快速增加后缓慢增至基本不变。相同光强（低于42 mW·cm^-2）和湿度条件下，红、绿、蓝光源的甲醛转化率相近，白光略低于其他光源。干气氛下，光反应和暗反应的甲醛转化率几乎为0。湿气氛下，光反应和暗反应均有甲醛转化率，光反应的甲醛转化率更高。不同光源条件下甲醛转化率随相对湿度变化规律相似。相对湿度为21.9%时甲醛转化率最高，而后保持不变，基本在80%左右。通过对红、绿、蓝、白光的数据拟合计算，得到表观动力学参数k（I）_H、k（H）_I、k（I，H）以及速率方程。

关键词: Au/TiO₂, 甲醛, 光催化, 可见光, 动力学, LED, 光化学, 数值分析