摘要
经电角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，只有当氧的吸附湿度低于185K时，才能观察到表面未解离的分子氧吸附物种，随着吸附湿度的升高，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^18O2与^16O2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。
The adsorption of oxygen on electrolytic silver surface has been investigated by
ultra-violet photoelectron spectroscopy (UPS), and by measurement of work function
ohange and of kinetic. UPS difference spectra show three positive peaks at about 3.0, 5.3
and 9.0 eV below Fermi level, which are due to the adsorbate resonances of atomic and
molecular oxygen on sliver surface, respectively. The peak at 5.3 eV indicates that the
orbitals derived from the л_g~* of molecular oxygen are electronically filled in the adsorbed
dioxygen complex and the peak at 9.0 eV corresponds electron feedback from the л_u of
dioxygen species to valence orbits of sliver. This bonding configuration is also supported
by the changes of work function. The kinetic results show a maximum (S_(max)=9.3×10^(-3)
In the sticking coefficient curve at room temporature. The temperature effects, S=k×
exp(550/T), have been observed by the measurement of kinesics, and the results aro
discussed in terms of precursor adsorption models.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
1989年第8期779-782,共4页
Acta Chimica Sinica
