Cu/盘状ZnO模型催化剂催化CO2加氢反应中生成CO的活性位研究

通过水热法合成盘状ZnO,并在其表面负载Cu得到Cu/盘状ZnO模型催化剂,将不同气氛下(5%CO/Ar、2.5%H_2/2.5%CO/Ar、5%H_2/Ar,分别记为CZ-5CO、CZ-2.5H_2-2.5CO、CZ-5H_2)还原的模型催化剂用于逆水煤气变换反应.对催化剂进行热重分析(TGA)、X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、原位紫外拉曼光谱(in situ UV-Raman)表征.结果表明,不同的还原气氛可得到不同尺寸的Cu颗粒及不同缺陷浓度的Cu-ZnO界面.CO_2程序升温脱附(CO_2-TPD)结果表明,不同的Cu-ZnO界面具有不同的CO_2活化能力.其中CZ-5H_2形成的Cu-ZnO界面对CO_2活化能力最强,表现出最佳的逆水煤气变换反应活性;CZ-5CO具有更多的表面缺陷可能是由于存在Cu_3Zn合金,但Cu-ZnO界面上CO_2的吸附容量降低,导致逆水煤气变换反应活性低;CZ-2.5H_2-2.5CO的活性介于CZ-5H_2与CZ-5CO之间,界面对CO_2的活化量也介于两者之间.

The active sites study of Cu/ZnO plate model catalyst for CO2 hydrogenation to CO

ZnO plate was synthesized by hydrothermal method, and Cu was loaded on the surface of ZnO to obtain Cu/ZnO plate model catalyst. The catalyst was reduced under different atmospheres (5%CO/Ar, 2.5%H₂/2.5%CO/Ar, 5%H₂/Ar, labeled as CZ-5CO, CZ-2.5H₂-2.5CO, CZ-5H₂, respectively) and then evaluated for the reverse water gas shift reaction. Specifically, the catalysts were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and in situ UV-Raman spectroscopy. The results indicate that the treatments under different reducing atmospheres can result in different Cu particle sizes and Cu-ZnO interfaces with different surface defect concentrations. And CO₂ temperature programmed desorption (CO₂-TPD) results show that different Cu-ZnO interfaces possess different CO₂ activation capabilities. The Cu-ZnO interface formed in CZ-5H₂ has the strongest CO₂ activation ability and exhibits the best reverse water gas shift reaction activity. CZ-5CO has much more surface defects which may be due to the presence of Cu₃Zn alloy, leading to lower CO₂ adsorption capacity at the Cu-ZnO interface, resulting in low activity for reverse water gas shift reaction. In addition, the activity and the CO₂ activation amount of CZ-2.5H₂-2.5CO at the interface are both between those of CZ-5H₂ and CZ-5CO.