【摘要】 甲烷作为一种无污染的清洁能源,具有储量丰富、环境友好的特点,因此,发展高效稳定的甲烷氧化催化剂具有十分重要的意义。通过两步浸渍法成功制备了铋掺杂的铂基铈-锆-镧催化剂,并将其应用在甲烷完全氧化反应。通过X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)表征,铋(Bi)和铂(Pt)之间存在较强的相互作用,促进了Pt物种分散到原子簇和单原子级别。然而,Bi的引入会导致Bi/BiOx原子簇覆盖催化剂表面的Pt物种(单原子和原子簇)和载体表面,阻碍了Pt活性物种以及载体与反应物的接触,从而降低了催化剂在甲烷完全氧化中的活性。通过XAFS指认铂与铋之间强相互作用的存在,这对于今后的双金属催化剂的制备具有一定的指导意义。更多还原

【Abstract】 [Background] Methane is a kind of clean energy with the characteristics of no pollution, abundant reserves and friendly environment. It is of great significance to develop efficient and stable methane oxidation catalysts to catalyze methane oxidation. [Purpose] This study aims to detect the interaction between platinum(Pt)and bismuth(Bi) species and their "structure-activity" relationship in methane oxidation through X-ray absorption fine structure(XAFS) technology. [Methods] First of all, the CeZrLaOx support was prepared by hydrothermal method. Then, the platinum and bismuth species were deposited on the surface of CeZrLaOx support via two-step impregnation method with calcination temperature at 700 ℃. The structure-activity relationship of platinum-bismuth catalyst in methane oxidation was characterized by the X-ray diffraction(XRD), the X-ray photoelectron spectroscopy(XPS) and high angle annular dark field image-scanning transmission electron microscope(HAADF-STEM). Finally,the X-ray Absorption Fine Structure(XAFS) of samples was measured at BL14W1 beamline of Shanghai Synchrotron Radiation Facility(SSRF). [Results] Experimental results show that the dispersion of platinum through strong interaction between platinum and bismuth is enhanced by the doping of bismuth species as confirmed by XRD and hydrogen temperature program reduction(H2-TPR). However, results of XPS and HAADF-STEM indicate that overmuch Bi or BiOxspecies hinders the contact between platinum and methane molecule, hence leads to low activity. [Conclusions] The strong interaction between platinum and bismuth species confirmed by XAFS technique markedly enhances thermo-stability of catalysts and gives some guiding significance for the preparation of bimetallic catalysts.更多还原