Mg-ZnO复合物的紫外光催化效率及协同作用研究

doi:10.7503/cjcu20190467

摘要/Abstract

摘要：

采用化学沉淀法合成了一系列Mg-ZnO光催化剂. 研究了在Mg ²⁺和MgO绝缘介质共同作用下Mg-ZnO光催化剂的活性. 结果表明, 紫外光照射5 min后, 10%Mg-ZnO复合物对10 mg/L RhB的降解率达到81.3%, 光降解速率常数为0.3271 min ^-1, 是纯ZnO的3.42倍. 瞬态光电压(TPV)、接触电势差、表面光电流(SPC)和Cr(Ⅵ)还原等实验结果表明, MgO绝缘颗粒的形成抑制了ZnO中光生电子的“逆向”传输, 使电子和空穴的复合时间延长, 从而间接提高了光生空穴的利用率.

关键词: 镁掺杂氧化锌, 光催化, 协同作用, 光生电荷行为

Abstract:

A series of Mg-doped ZnO samples were synthesized via a facile chemical precipitation method. Mg ²⁺ was effectively doped into the lattice of ZnO and MgO particles formed on the surface of ZnO when the Mg doping content exceeded 5%. Under the combined action of Mg ²⁺ and MgO insulators, the degradation rate of RhB over 10%Mg-ZnO photocatalyst was 81.3% in 5 min under ultraviolet light and the degradation rate constant was 0.3271 min ^-1, which was 3.42 times that of pure ZnO(0.0957 min ^-1). The transient photovoltage(TPV) and the contact potential difference(ΔCPD) measurements directly demonstrated that the incorporation of Mg ²⁺ decreased the work function of ZnO and increased the number of electrons in the conduction band, thus the separation efficiency of photogenerated electrons and holes can be improved. The surface photocurrent(SPC) and the Cr(Ⅵ) reduction experiments showed that the formation of MgO insulating particles inhibited the “reverse” transmission of photogenerated electrons in ZnO, which prolonged the recombination time of electrons and holes, thus indirectly improved the utilization of photogenerated holes. This work provides a new idea for the design of highly efficient photocatalytic materials.

Key words: Mg doped ZnO, Photocatalysis, Synergetic effect, Photogenerated charges behavior

中图分类号:

O643

TrendMD:

赵鹏,张晋腾,林艳红. Mg-ZnO复合物的紫外光催化效率及协同作用研究. 高等学校化学学报, 2020, 41(3): 538.

ZHAO Peng,ZHANG Jinteng,LIN Yanhong. Excellent Ultraviolet Photocatalytic Efficiency of Mg ²⁺ Doped ZnO and Analysis on Its Synergetic Effect ^†. Chem. J. Chinese Universities, 2020, 41(3): 538.

图/表 14

Fig.1 XRD patterns for pure ZnO and Mg-ZnO composites

Table 1 Grain size and lattice parameters of the samples

Sample	Crystallite size/nm	a/nm	c/nm	c/a ratio
ZnO	22.0	0.32432	0.52001	1.6034
1%Mg-ZnO	20.5	0.32397	0.51973	1.6043
3%Mg-ZnO	19.6	0.32509	0.52047	1.6010
5%Mg-ZnO	19.3	0.32569	0.52135	1.6007
10%Mg-ZnO	19.3	0.32584	0.52109	1.5992
20%Mg-ZnO	21.6	0.32573	0.52093	1.5993

Fig.2 FESEM images of pure ZnO(A), 1%Mg-ZnO(B), 3%Mg-ZnO(C), 5%Mg-ZnO(D), 10%Mg-ZnO(E) and 20%Mg-ZnO(F)

Fig.3 TEM(A) and HRTEM(B) images of 10%Mg-ZnO composite

Fig.4 Survey XPS spectra(A) and high-resolution XPS spectra of Zn2p(B), O1s(C), Mg1s(D) of 10%Mg-ZnO composites

Fig.5 N2 adsorption-desorption isotherms of ZnO(A) and 10%Mg-ZnO(B)

Fig.6 UV-Vis DRS spectra(A) and (αhν)1/2-hν plots of the as-prepared photocatalysts(B)

Fig.7 ΔCPD values of ZnO and 10%Mg-ZnO composites samples

Fig.8 TPV plots of pure ZnO and 10%Mg-ZnO composites samples

Fig.9 SPC plots of ZnO and different molar ratio of Mg-ZnO samples

Fig.10 RhB decolorization curves over different catalysts under UV lamp irradiation(A), first-order kinetic fitting for the degradation of RhB over different catalysts(B) and UV-Vis spectra of 20 mg/L RhB over pure ZnO(C) and 10%Mg-ZnO(D)

Fig.11 Effect of different scavengers on the photode-gradation efficiency of RhB under UV light

Fig.12 Results of Cr(Ⅵ) reduction in the presence of pure ZnO and 10%Mg-ZnO

Fig.13 Photogenerated charge separation and transport mechanism of Mg-ZnO under ultraviolet light

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