The scale of time is important in chemistry. A typical catalytic reaction has turnover frequencies ranging from 0.01 to 10 or even 103 s-1. A complete turnover usually contains adsorption of reaction molecules, surface migration and several steps of elementary reaction, and finally the desorption of the product. Among which, the surface elementary reactions are believed to be the fastest step that in the range of 10-15 s (femtosecond). To measure these ultrafast bond breaking and formation process, the so-called X-ray free electron lasers (XFEL) with even faster pulses have been developed as the 4th generation of light sources. Here I will present our preliminary work that determines the breaking of Cu-O bond over CeO2 surface within 1 ps. This is achieved by measuring the dynamics of the Cu L3 edge Near edge X-ray absorption fine structure with the pump probe technique at Pohang Accelerator Laboratory – XFEL (PAL- XFEL). Our first study of the CuO-CeO2 dated back to 2013. A range of operando methods have been used to understand the redox between Cu and Ce in these eight years. From electron paramagnetic resonance to synchrotron X-ray based techniques, the time resolution has been improved from minutes all the way to femtosecond scale, providing a complete picture of surface catalysis. XFEL provides the fastest X-ray pulses that shoot molecular movies within a single turnover.
Dr. Feng Ryan Wang is an associate professor at the chemical engineering department of UCL. He obtained his PhD in Chemistry at Peking University in 2012. He was an Alexander von Humboldt Research Fellow at the Max-Planck Institute für Kohlenforschung between 2013 and 2015. He joined the UK catalysis community in 2016, and has been actively engaged with the UK Catalysis Hub and Diamond Light Source. His research mainly focuses on the time and space resolved operando methods in heterogeneous catalysis, in particular in Cu related catalytic systems. He has been awarded the Young Scientist Prize of the 16th International Congress of catalysis. He is now serving the ePSIC User working group at Diamond Light Source, the EPSRC strategic advisory team on capital equipment and the Early Career Advisory Board of ChemCatChem.
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