基于水滑石前驱体制备ZnCr_2O_4-ZnO复合光催化剂及产氢性能

Preparation of ZnCr_2O_4-ZnO composite photocatalyst based on the hydrotalcite precursor and its performance in hydrogen production

以研磨水热法合成ZnCr_2O_4-ZnO异质结型光催化剂,对所得样品进行了TG-DTA、XRD、SEM、HRTEM、DRS和N2吸附-脱附表征分析;在模拟太阳光下,以草酸为牺牲剂对样品的光催化产氢活性进行评价,并分别与共沉淀法、尿素回流法和尿素水热法制备的ZnCr_2O_4-ZnO样品进行比较,探讨了异质结型ZnCr_2O_4-ZnO复合光催化剂的产氢机理。结果表明,四种方法制备的Zn-Cr前驱体都具有一定的水滑石结构,经500℃焙烧后,均为球形纳米粒子,但团聚情况各异,比表面积和孔结构参数有较大差别。其中,研磨水热法所得样品ZnCr_2O_4-ZnO粒子均匀,光电流响应强度最大,产氢效率最高,为0.956 mmol/(h·gcat),分别是共沉淀法、尿素回流法和尿素水热法制备样品产氢量的2.3、1.5和3.0倍。

ZnCr2O4-ZnO composite photocatalyst with heterogeneous structure was synthesized by grinding hydrothermal method and characterized by TG-DTA,XRD,SEM,HRTEM,DRS,and N2 absorption; its photocatalytic activity in H2 production was evaluated by using oxalic acid as the sacrificial agent under simulated sunlight irradiation and compared with those of the ZnCr2O4-ZnO samples prepared by coprecipitation,urea reflux and urea hydrothermal methods. The results indicate that Zn-Cr precursors prepared by four methods show a certain hydrotalcite structure; the catalyst samples prepared at 500 ℃ are spherical nanoparticles,but different in agglomeration status,specific surface area and pore structure parameters. The ZnCr2O4-ZnO nanoparticles prepared by a grinding hydrothermal method exhibits the optimized photocurrent response and photocatalytic activity; the yield of hydrogen production is 0.956 mmol/（ h·gcat）,which is 2.3,1.5 and 3.0 times higher than that of the catalyst samples prepared by coprecipitation,urea reflux and urea hydrothermal methods,respectively.On the basis of these results,a possible mechanism for the hydrogen production over ZnCr2O4-ZnO composite photocatalyst with heterogeneous structure was then proposed.