Ultrafast catalytic dynamics unveiled with UV pump - X-Ray probe experiment and simulations

Understanding of charge transfer and chemical bond breaking processes is key to gaining a deeper insight into catalytic activity and selectivity and identifying new catalyst materials. With the development of X-ray free-electron laser (XFEL) facilities around the world, X-ray spectroscopy in pump-probe experiments will be an essential tool for unveiling unprecedented details of heterogeneous catalytic reactions with femtosecond time resolution. A femtosecond UV pump laser will excite the system and initiate the charge transfer and bond breaking process, and the absorption spectra of the probe X-ray laser pulses record the dynamics. Due to the large amount of information in the X-ray absorption spectra (XAS) and the vast amount of competing reaction pathways, it is a huge challenge to discriminate the many potentially observed reaction intermediates from the spectra. Our theoretical calculations simulate the charge transfer dynamics and provide the X-ray absorption spectra for each snapshot of the chemical reaction, which is comparable to the transient XAS recorded in the experiment. As an example, we present here the charge transfer dynamics between a transition metal catalyst and graphene. Our simulation method will provide detailed dynamics for the temporal evolution of surface reactions for a wide range of catalytic processes in future studies.