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Untersuchungen zur Physisorption und Chemisorption von Wasser auf Zinkoxid‐Oberflächen
Author(s) -
Mattmann G.,
Oswald H. R.,
Schweizer F.
Publication year - 1972
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19720550421
Subject(s) - chemistry , physisorption , chemisorption , hydroxide , adsorption , zinc hydroxide , zinc , carbonate , molecule , infrared spectroscopy , inorganic chemistry , analytical chemistry (journal) , organic chemistry
The investigation of different zinc oxide samples by means of thermogravimetry and infrared spectroscopy has shown that the surface of the samples is covered by an approximately monoatomic layer of hydroxide groups. Furthermore, varying amounts of carbonate groups are found which are due to the presence of zinc hydroxide carbonate II [Zn 5 (OH) 6 (CO 3 ) 2 ]. Below relative water vapour pressures of p/p 0 = 0.2 (25°C), two hydrogen bridges connect one physisorbed water molecule with two chemisorbed surface hydroxide groups. In addition, about the same amount of water is physically adsorbed between vapour pressures of p/p 0 0.2 and 0.8. At still higher relative humidity, a multimolecular layer is built up which reaches a thickness of about 200 water molecules at p/p 0 = 1.0. All samples show in the v ‐OH region of the IR. spectrum a broad absorption with four bands, A, B, C, and D. The position of the bands and the change of their intensities when rising the temperature of the samples up to 600°C indicate that both bands of longer wave lengths, C and D, arise from physically adsorbed water molecules, while the bands A and B are due to hydroxide groups located on the crystallographic faces (0001) and (000 1 ), respectively.