Physics and theory of the photoexcitation process (WP3)

 

Description of the Work Package

 

In this workpackage, the underlying physics at the origin of the emission of solvated electron from diamond materials in water will be unraveled from experimental and theoretical perspectives.

 

Diamond materials synthesized for the DIACAT project will be characterized directly in water using X-ray spectroscopy at the BESSY II synchrotron in Berlin. By exciting electrons in the diamond materials with X-rays, it is possible to obtain a global picture of the diamond electronic structure and observe how it is impacted by water and light exposure. These experimental results will be compared to computer simulations to achieve a higher understanding of the electronic structure of the diamond-water interface.

Understanding the process of electron emission in water require the use of ultrafast spectroscopy, which will follow the evolution of electrons at extremely small timescale (~10-15 seconds). After excitation of the diamond by a first laser pulse, electrons will then be extracted by a second pulse. By analysing the energy of the photo-emitted electrons, the energies of the solvated electrons, forming upon illumination of diamond material in solution, will be measured. Additionally, by changing the time delay between the two pulses, the lifetime of the solvated electrons can be probed.The rate of electron transfer will also be estimated by time-dependent calculations to provide further insights about the electron emission process in water.

The impact of diamond material properties (such as doping, morphology, surface chemical groups,…) on the electronic structure and the electron emission efficiency will be estimated from the previous experiments. Optimization of energy up-conversion using optical nearfield excitation as a mean for the direct use of sunlight for the excitation of electrons will also be investigated. Based on this knowledge, the key parameters to provide an efficient diamond-based system toward CO2 reduction will be unravelled.

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