乙二醇溶剂热合成的CeO_2的可逆氧化还原性及CO_2捕获性能

Redox properties and CO_2 capture ability of CeO_2 prepared by a glycol solvothermal method

利用乙二醇的还原性,采用乙二醇溶剂热法制备了表面具有丰富氧空穴的CeO2-GST纳米晶,对其进行了X射线衍射、透射电镜、X射线光电子能谱、原位H2还原-O2氧化循环和CO2原位红外漫反射表征,并研究了其可逆氧化还原性及CO2捕获性能.结果表明,与CeO2-nanorod和柠檬酸溶胶法合成的CeO2-CA样品相比,CeO2-GST纳米晶具有最好的可逆氧化还原性能和循环稳定性,同时在50 oC下具有最好的CO2吸附性能(149μmol/g).利用原位红外漫反射光谱研究了CO2在还原CeO2表面的吸附情况,发现CO2主要以双齿碳酸盐和桥连碳酸盐两种形式吸附在CeO2表面,其中桥连碳酸盐物种不稳定,He吹扫可脱附.此外,CO2在CeO2-nanorod上还会生成稳定的甲酸盐和单齿碳酸盐物种.

CeO2 nanocrystals with plentiful oxygen vacancies were synthesized by a glycol solvothermal method （CeO2‐GST） using the strong reducibility of glycol. For comparison, CeO2 nanorods（CeO2‐nanorods） and CeO2 nanoparticles（CeO2‐CA） were also prepared. The samples were charac‐terized by X‐ray diffraction, transmission electron microscopy, X‐ray photoelectron spectroscopy, H2 reduction‐O2 oxidation cycle experiments and in situ CO2 infrared spectroscopy. The CeO2‐GST sample exposed mainly（111） facets with abundant Ce3＋ ions on its surface, and it gave excellent reversible redox behavior and high oxygen storage capacity. After seven H2 reduction‐O2 oxidation cycles, the oxygen storage capacity became stable. The CeO2‐GST sample also had a high CO2 ad‐sorption capacity of 149 μmol/g at 50 ℃ by forming bidentate and bridge carbonates on the CeO2surface. These carbonate species were less stable than the unidentate carbonate, bicarbonate and formate species, thus adsorbed CO2 was released easily. On reduced CeO2 nanorod, CO2 formed the stable unidentate carbonate and formate species, which is unfavorable for the release of adsorbed CO2.