Transition metals and non-ferrous metals such as copper, nickel and cobalt are not only suitable as materials in engineering and technology, but also for a wide range of applications in electrochemistry and catalysis. Their chemical and physical properties are related to the occupation of the outer d-orbital shells around the atomic nuclei. The energetic levels of the electrons as well as their localisation or delocalisation can be studied at the X-ray source BESSY II, which offers powerful synchrotron radiation.
Copper, Nickel, Cobalt
The team of the Uppsala-Berlin Joint Lab (UBjL) around Prof. Alexander Föhlisch and Prof. Nils Mårtensson has now published new results on copper, nickel and cobalt samples. They confirmed known findings for copper, whose d-electrons are atomically localised, and for nickel, in which localised electrons coexist with delocalised electrons. In the case of the element cobalt, which is used for batteries and as an alloy in fuel cells, however, previous findings were contradictory because the measurement accuracy was not sufficient to make clear statements.
Spectroscopy combined with highly sensitive detectors
At BESSY II the Uppsala-Berlin joint Lab has set up an instrument which enables measurements with the necessary precision. To determine electronic localisation or delocalisation, Auger photo-electron coincidence spectroscopy (APECS) is used. APECS requires the newly developed "Angle resolved Time of Flight" (ArTOF) electron spectrometers, whose detection efficiency exceeds that of standard hemispherical analysers by orders of magnitude. Equipped with two ArTOF electron spectrometers, the CoESCA@UE52-PGM end station supervised by UBjL scientist Dr. Danilo Kühn is unique worldwide.
Analysing (catalytical) materials
In the case of the element cobalt, the measurements now revealed that the d-electrons of cobalt can be regarded as highly delocalised. "This is an important step for a quantitative determination of electronic localisation on a variety of materials, catalysts and (electro)chemical processes," Föhlisch points out.
Guest users are welcome
The Royal Society of Chemistry has therefore selected the paper as a HOT Article 2022, also because this measurement method might arouse broad interest in the broader research community. The end station is also available to international users at BESSY II, who can apply for beamtime twice a year.
Physical Chemistry Chemical Physics
Method of Research
Subject of Research
The degree of electron itinerancy and shell closing in the core-ionized state of transition metals probed by Auger-photoelectron coincidence spectroscopy
Article Publication Date