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

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。

Preparation of ZnCr2O4-ZnO composite photocatalyst based on the hydrotalcite precursor and its performance in hydrogen production

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·g_cat), 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.