Determining the active site in a catalytic process: Operando spectroscopy is more than a buzzword

Determining the active site in a catalyst material and elucidating the related reaction mechanism remain intellectual challenges and are of paramount importance for the rational development of new or better catalysts. Identifying active sites should in principle be possible by studying the catalyst at its working place under real reaction conditions. This is the field of operando spectroscopy, a research area, which is under intense development and of high interest to the catalysis community. This feature article presents an attempt of a roadmap for future operando spectroscopy studies. Two case studies will illustrate the potential and limitations of the operando approach. A first study deals with operando vibrational spectroscopy to obtain mechanistic insight in the destruction of chlorinated hydrocarbons with steam over lanthanide oxide-based catalysts. The second case study elaborates on the use of operando electronic spectroscopy to elucidate the active alkane dehydrogenation site in supported chromium oxide catalysts.