Photoionization Mass Spectrometry for Online Detection of Reactive and Unstable Gas-Phase Intermediates in Heterogeneous Catalytic Reactions

Heterogeneous catalytic reactions always involve surface intermediates on catalyst surfaces, and some of them also involve reactive and unstable gas-phase intermediates such as radicals and alkyl hydroperoxides. Online detection of these gas-phase intermediates is of great importance for fundamentally understanding reaction mechanisms of relevant heterogeneous catalytic reactions, designing structures of efficient catalysts and optimizing reactors. However, it has remained a long-time challenge due to the lack of routine characterization techniques. Herein we review recent progress on applications of photoionization mass spectrometry in online detection of reactive and unstable gas-phase intermediates in heterogeneous catalytic reactions. The development and advantages of photoionization mass spectrometry and the relevant equipment setup for heterogeneous catalysis studies are also described. Finally, a future perspective is given.