Missions

Photocatalysis allows to convert solar energy into green hydrogen without greenhouse gas emissions, but its efficiency still needs to be improved to become competitive on an industrial scale. It has already been shown that heterostructures combining n-type semiconductors, such as g-C3N4, le BiVO4 et le TiO2 and metallic co-catalysts (Au, Pt) can enhance the transport of photogenerated charge carriers in photocatalysts and thus increase the photoconversion efficiency. However, a deeper understanding of the dynamic processes occurring in these systems under working conditions is still necessary.The objective of this work is to study the formation and evolution of these heterostructures at the nanometer scale during photodeposition and photocatalytic reactions, using in situ transmission electron microscopy (TEM) in representative liquid environments and under light excitation. This will make it possible to understand the relationship between the structure of photocatalysts and their evolution on one hand, and their catalytic properties on the other, thereby contributing to the design of more efficient materials.
A more detailed list of activities for which the candidate will be responsible is presented below:

Activities

• Characterization of semiconductor photocatalysts (TiO₂, BiVO₄, g-C₃N₄) decorated with metal co-catalysts (Pt and Au) using transmission and scanning electron microscopy (TEM/SEM), X-ray diffraction (XRD), UV-visible spectroscopy, photoluminescence spectroscopy, and X-ray photoelectron spectroscopy (XPS).
• Set-up of a photo-excitation source allowing to bring UV-vis light inside the TEM column, and focus it on the sample during in situ measurements.
• Develop an acquisition protocol for in situ TEM measurements during UV-vis irradiation to understand the combined effect of the electron beam and UV-vis photons on sample evolution, and to minimize the dose rate and beam damages.
• In situ TEM experiments in liquid phase during photoexcitation with UV-vis light, to monitor in real time the nucleation, growth, and evolution of n-type semiconductor photocatalysts decorated with nanoparticles under real photo-catalytic working conditions.
• Analysis and correlation of structural and chemical changes observed by in situ TEM with the measured photocatalytic performance, to identify the parameters governing the efficiency of charge carrier separation and transfer.
• Scientific dissemination of results through publications in international journals and presentations at conferences.

Skills

• Strong expertise in transmission electron microscopy
• Capacity to develop new protocols of in situ characterization on the microscope JEOL Grand ARM2.
• Capacity to understand and speak scientific english
• Capacity to write articles and reports in english
• Expertise in photocatalysis is appreciated but not required.
• Expertise in coding is appreciated but not required

Work Context

The candidate will join the CNRS Institut de Physique et Chimie des Materiaux de Strasbourg (IPCMS). The project will be carried out in collaboration between the 3D-TEM team at IPCMS (supervisors: M.L. De Marco and O. Ersen) and the Photocatalysis and Photoconversion team at ICPEES (supervisor: T. Cottineau).
The 3D-TEM team's expertise lies in the in situ transmission electron microscopy (TEM) study of energy materials, both in gaseous and liquid environments, as well as in 3D reconstruction by TEM tomography of nanostructured and fragile materials. Within the group, we have sample holders for in situ experiments in both gaseous and liquid environments and three electron microscopes: JEOL 2100, JEOL 2100F, and JEOL Grand ARM2.
The JEOL Grand ARM2 microscope will be used for in situ photo-excitation measurements. This microscope is already equipped with a photo-excitation system (MicroLuminary by IDES), composed of an ensemble of focusing lenses, mirrors, and windows, allowing to focus light generated by an external source, on the sample located within the environmental sample holder inside the TEM column. This experimental set-up allows the characterization in situ of the formation and evolution of photo-catalysts under UV-vis light illumination in liquid or gas phase.
The Photocatalysis and Photoconversion team at ICPEES has recognized expertise in the design and characterization of semiconductor materials for photoconversion applications (such as depollution and solar fuels). The team also possesses a unique photocatalytic characterization platform in France, notable for its standardization and versatility of light sources.
Overall, this project will be closely linked to the ANR OSCARE and PEPR LUMA Visible projects, which aim at the rapid characterization of heterostructures.
Both research institutes, the IPCMS et ICPEES, are in the Cronenbourg campus, 20 minutes away from Strasbourg city centre with public transport (bus line G). The campus is also provided with an on-site restaurant for the staff of the research institutes.
The project duration is one year, with the possibility of renewing the contract (1 year + 1 year).

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.