掺Cu对MoO_3-TiO_2/SiO_2上光促甲烷和水表面反应的影响

Effect of Doped Cu^(2+) on Photo-Stimulated Surface Reaction between Methane and Water over MoO_3-TiO_2/SiO_2

固定床环隙反应器中 ,借助紫外光的激发 ,气相甲烷和水在MoO3 TiO2 /SiO2 催化剂表面生成了甲醇和氢气 ,当在催化剂中掺杂Cu2 + 后 ,光催化剂的活性明显提高 .XRD ,IR ,UVDRS和TPD的研究结果表明 ,在催化剂表面形成了具有Mo O Ti和Mo O Cu基元的高度分散物种 ,不但使得吸光带边明显蓝移 ,而且扩展了催化剂的光响应范围 .所形成的复合结构还可以优化单组分的吸光性能并促进对反应物分子的吸附活化 ,同时可以有效地转移光生电子和空穴 .掺杂Cu2 + 能够进一步延长光生电子 空穴对的寿命 ,进而提高反应的量子产率 .

MoO 3-TiO 2/SiO 2 and Cu 2+-doped MoO 3-TiO 2/SiO 2 were prepared by impregnating 5.3%TiO 2/SiO 2 that was prepared by the chemical modification method, and they were used for gas-phase photo-catalytic production of CH 3OH and H 2 from CH 4 and H 2O in a fixed-bed annular photo reactor under UV irradiation. The selective formation of CH 3OH may be attributed to the coupled effect of MoO 3 and TiO 2, and the photo quantum yield of CH 3OH is markedly enhanced after Cu 2+ introduction. Results of XRD, UVDRS, IR and TPD showed that the well-dispersed surface coupled species comprising Mo-O-Ti and Mo-O-Cu bonds are formed on the catalyst surface, and they make the photo absorption threshold blue shift due to the quantum size effect. Compared with TiO 2/SiO 2 and MoO 3/SiO 2, the photo absorption capacity, adsorption and activation ability for CH 4 and H 2O of MoO 3-TiO 2/SiO 2 and Cu/MoO 3-TiO 2/SiO 2 are effectively enhanced. During the photo-stimulated surface catalytic reaction, the O- hole centers created by the charge-transfer excitation can enhance the activation of CH 4, and the active species O- can be stabilized when the photoelectron is transferred by reduction of Cu 2+ to Cu+. The possible reaction mechanism was discussed.