Polaronic Dynamics of Photo-electrocatalysts under Chemical and Photonic Excitation Probed by Spectroscopies across Different Timescales (M/F)

Job Description

Thesis Subject

Funded by the Mission for Transversal and Interdisciplinary Initiatives (MITI) of the CNRS, this PhD project aims to quantitatively characterize photo-excited carriers in TiO₂ and SrTiO₃ photoelectrocatalysts, by determining their polaronic mobility, their degree of localization, and the lifetime of intra-gap Ti³⁺ states. In these oxides, charges become trapped or recombine before reaching the reactive sites, directly limiting photocatalytic efficiency. The challenge is to distinguish, via the Ti³⁺ signature, a mobile polaron from trapped states that constitute irreversible loss channels, and to identify the operando conditions that sufficiently preserve this mobility to enable efficient surface photochemistry. The comparative study of TiO₂ (rutile/anatase) vs. SrTiO₃ ultimately allows the conclusions to be generalized beyond a single material.

The project relies on coordinated campaigns combining synthesis and multi-scale spectroscopy. The materials, synthesized at IRCELYON with independent control of phase, doping, and defects, will be characterized there by XPS/UPS in static mode and under photonic excitation, in order to establish the reference electronic state of the surfaces and monitor its evolution. THz spectroscopy will then provide access to the conductivity and mobility of photo-induced polarons. These results will serve as a reference for large-scale facility campaigns: time-resolved photoemission (tr-PES) at the European XFEL (solid-liquid interface) and resonant inelastic X-ray scattering (RIXS) under operando conditions at the Ti K-edge on the GALAXIES beamline at the SOLEIL synchrotron. The photocatalytic and photoelectrochemical performances measured on the same series of materials will directly anchor the spectroscopic observables to the catalytic results, leading to a unified methodology that transforms the Ti³⁺ signal from a qualitative fingerprint into a quantitative indicator of carrier mobility and lifetime, applicable under vacuum, under operando conditions, and at the solid-liquid interface.

Your Work Environment

The doctoral candidate will be primarily based at IRCELYON (UMR 5256, CNRS / Université Claude Bernard Lyon 1, Villeurbanne), the laboratory where the thesis will be registered. There, they will carry out materials synthesis activities, physicochemical characterization (UV/XPS, THz), as well as the study of photocatalytic and photoelectrochemical properties. The thesis will be supervised by Luis Cardenas (IRCELYON, IRL CNRS-EuXFEL), with co-supervision by Mathieu Prévot (IRCELYON) and Iyas Ismail (LCPMR).

The project will also include several experimental campaigns at international research infrastructures. tr-PES experiments will be conducted at the European XFEL, while RIXS experiments will be carried out at the SOLEIL synchrotron. The LCPMR group benefits from in-house access to the SOLEIL synchrotron, ensuring regular access for RIXS campaigns. The doctoral candidate will actively participate in the preparation, execution, and analysis of experiments at large-scale facilities.

This thesis will provide the doctoral candidate with multidisciplinary training covering the synthesis and characterization of functional materials, advanced electronic and optical spectroscopies, as well as the preparation and execution of large-scale facility experiments. The candidate will also develop skills in the processing and analysis of large data volumes from XFEL experiments, in multimodal data analysis, and in the interpretation of ultrafast electronic processes. The results obtained will be published in international journals and presented at scientific conferences. The doctoral candidate will thus work within an international and multidisciplinary research environment.

Constraints and risks

The doctoral candidate must be available to travel to various large-scale research facilities.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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