Mössbauer Spectroscopy in Heterogeneous Catalysis

International audienceMössbauer spectroscopy dates back to 1958 and for characterization of a solid catalyst was first used in 1971; the technique achieved a high point in the 1980s and has been applied only modestly for catalyst characterization since then. The declining use of the technique may be related to the experimental difficulties and the complexity of the spectral analysis. However, the adaptability of Mössbauer spectroscopy to the investigation of catalysts under working conditions and the progress made in the field are evidently leading to a reawakening of interest in its application in catalysis. The value of Mössbauer spectroscopy in catalyst characterization is illustrated by results of investigation of Fischer–Tropsch catalysts by 57Co Mössbauer emission spectroscopy performed at temperatures up to 723 K and pressures up to 40 bar corresponding to industrial working conditions. Furthermore, synchrotron Mössbauer techniques have reached a level of maturity that today allow their use for applications from which catalysts characterization would benefit. This review includes a brief summary of the technique and an overview of applications in catalysis. The majority of investigations have dealt with the isotopes 57Fe, 119Sn, and 57Co (in emission mode). In contrast, investigations focusing on other isotopes, such as 197Au, 121Sb, 125Te, 193Ir, or 99Ru, have been limited in number but very fruitful. Opportunities for future applications to working catalysts are presented and discussed. New techniques related to the use of synchrotron radiation as energy source are emphasized. Such techniques have been applied to isotopes other than 57Fe, such as 169Tm, 119Sn, 83Kr, 181Ta, 151Eu, 161Dy, and 149Sm. The investigation of isotopes such as 197Au, 197Pt, 61Ni, 186W, 99Ru, and 99Rh, is also possible and should strongly benefit catalyst characterization. An effort has been made here to present the techniques, results, and developments in a didactic manner