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经电解法制得的多晶银有很多独特的物理和化学性质,作为催化剂,用于甲醇氧化制甲醛的工业过程,不需要任何附载,得到了非常高的转化率和选择性;对这种高纯度的金属催化剂的理论研究可望能直接解释工业过程中的一些问题。由于表面结构的特殊性,与单晶银相比,氧在这种电解银上的吸附和脱附有很大的差别。在超高真空条件下,对氧在单晶银[如Ag(110)]吸附的研究结果表明,在清洁的Ag(110)表面,只有当氧的吸附温度低于185K时,才能观察到表面未解离的分子氧吸附物种,随着吸附温度的升高,分子氧解离为原子态,原子态吸附氧在表面的结构为(n×1),随着覆盖度的增加,n从7到2,饱和吸附时为0.5单层。XPS、TDS以及~(18)O_2与~(16)O_2同位素交换结果表明:电解银表面除了存在大量的解离的原子态吸附氧外,在室温下就能检测到表面存在的未解离的分子态吸附氧种。本文报道了用紫外光电子能谱(UPS),热脱附(TDS)和表面功函数连续测量等手段对氧与电解银表面相互作用过程中的电荷传递、成键以及吸附动力学等研究的实验结果。
Polycrystalline silver obtained by electrolysis has many unique physical and chemical properties, as a catalyst for the industrial process of methanol oxidation of formaldehyde, without any attachment, has been very high conversion and selectivity; for this high The theoretical study of the purity of metal catalysts is expected to directly explain some of the problems in industrial processes. Owing to the particularity of the surface structure, the adsorption and desorption of oxygen on this electrolytic silver are greatly different from that of single-crystal silver. The results of the adsorption of oxygen on single crystal silver [such as Ag (110)] under ultra-high vacuum show that the surface of the cleaned Ag (110) surface is observed only when the oxygen adsorption temperature is below 185 K With the increase of adsorption temperature, the molecular oxygen dissociates to the atomic state, and the structure of the atomic oxygen adsorbed on the surface is (n × 1). With the increase of the coverage, n changes from 7 To 2, 0.5 monolayer for saturated adsorption. The results of XPS, TDS and isotope exchange of ~ (18) O_2 and ~ (16) O_2 show that in addition to the presence of a large amount of dissociated atomic-state adsorbed oxygen on the surface of silver, the presence of undissociated Molecular absorption of oxygen species. In this paper, we report the experiments of charge transfer, bond formation and adsorption kinetics in the interaction between oxygen and silver surface by means of UV photoelectron spectroscopy (UPS), thermal desorption (TDS) and continuous measurement of surface work function result.