Static charge correction in XPS on Cu-Zn-Al oxide catalyst precursors with the help of deposited Pd particles as a reference material

• Published in: Applied surface science 1994-08, Vol.78 (4), p.345-355
• Main Authors: Gross, Th, Lippitz, A., Unger, W.E.S., Lehnert, A., Schmid, G.
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; General and physical chemistry; Photoemission and photoelectron spectra; Physics; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(94)90059-0

To obtain binding energy (BE) data from a photoelectron spectroscopy experiment (XPS) with poorly conductive samples, one needs a reliable inner BE reference. The problem of an inner static charge reference for Cu-Zn-Al oxide catalysts is studied on different samples including ZnO, defined hydroxycarbonates, precipitated precursors and calcined catalysts. With the help of an external reference material, i.e. deposited 20 ± 10 nm Pd particles, the suitability of the C 1s, Zn 2p 3/2 and Al 2s spectra to provide an inner static charge reference is tested. The Zn 2+ 2p 3/2 BE may serve as a reference when thoroughly calcined samples are exclusively investigated. Provided the Cu/Al surface concentration ratio is not to high, the Al 2s BE can be used in case of many calcined and precipitated samples when some care is taken. Considering C 1s BE related charge correction high systematic errors may occur due to the complexity of the C 1s spectra together with the known C 1s BE variation based on extra-atomic relaxation between the substrate and the contaminant hydrocarbon adsorbate.