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使用乙二醇还原法制备了一系列不同尺寸的Pt-x纳米颗粒(x=1.41、1.57、1.79、1.95、2.12、2.32 nm),将其负载于棒状(rod)CeO_2载体上.考察了不同尺寸的Pt颗粒催化剂Pt-x/CeO_2-rod在甲苯催化氧化反应中的催化性能.结果显示,随着Pt颗粒尺寸的增加,催化剂活性先升高后降低.其中,Pt颗粒尺寸为1.79 nm时催化剂催化活性最好,T90=133℃.一般认为,Pt颗粒尺寸增加其分散度减小,导致催化活性降低.然而本实验结果表明,随Pt尺寸增加催化活性先升高后降低,并且基于催化剂表面Pt原子计算的TOFs(turnover frequencies)随Pt尺寸增加逐渐变大.紫外拉曼光谱(UV Raman)、XRD、XPS显示,随着Pt颗粒尺寸增加,催化剂Pt-x/Ce-rod表面氧空位的浓度逐渐增加.氧空位有效提高了催化剂晶格氧的流动,促进了氧气的吸附活化及传递过程.Pt/Ce催化剂催化氧化甲苯反应活性是Pt分散度以及CeO_2表面氧空位浓度双重作用的结果.
A series of Pt-x nanoparticles with different sizes (x = 1.41, 1.57, 1.79, 1.95, 2.12, 2.32 nm) were prepared by ethylene glycol reduction method and supported on a rod CeO 2 carrier. The catalytic activity of Pt-x / CeO_2-rod catalyst in the catalytic oxidation of toluene was investigated.The results showed that the catalyst activity first increased and then decreased with the increase of Pt particle size.When Pt particle size was 1.79 nm The catalytic activity is the best, T90 = 133 ℃ .It is generally believed that the Pt particle size increases its dispersion decreases, resulting in decreased catalytic activity.However, the experimental results show that with increasing Pt size catalytic activity increased first and then decreased, and based on the catalyst The TOFs (calculated frequencies) of Pt atoms on the surface gradually increase with increasing Pt size.Ultraviolet Raman spectroscopy (XRD) and X-ray photoelectron spectroscopy (XPS) show that as Pt particle size increases, the oxygen vacancy of Pt-x / Ce- Oxygen vacancies effectively increased the lattice oxygen flow and promoted the adsorption and transfer of oxygen.The catalytic activity of Pt / Ce catalyst for toluene oxidation was doubled by the Pt dispersion and the oxygen vacancy concentration on the CeO 2 surface fruit.