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Univ. Paris-Saclay
Oxygen evolution reaction: the key to optimize photocatalytic water oxidation (01/04/2023 - 31/03/2027)
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OERKOP aims to understand and describe the mechanisms underlying the OER for co-catalyst modified hematite photoanodes, by using a correlative operando characterization approach at the nanoscale. OERKOP proposes a comparative study between two archetypal materials used as photoanodes: α-Fe2O3 and BiVO4, both catalytically activated by oxyhydroxide catalysts (M-OOH, with M = Fe, Ni, Co, Cu, Zn). Surface kinetics and time stability during the oxidation will be systematically evaluated. We intend combining multi-scale and multi-selective techniques - scanning transmission X-ray microscopy (STXM) and scanning transmission electron microscopy (STEM). Both techniques will employ a common sample environment in a dedicated photoelectrochemical cell. Complementary DFT calculations will allow dissecting complex effects and determining the reaction priorities of different photocatalytic sites.



Univ. Paris-Saclay
Synchrotron SOLEIL
Univ. de Strasbourg
Karine CHAOUCHI (Laboratoire de chimie)
Stephanie BLANCHANDIN (Laboratoire de chimie)




PhD 1: Bilal MEDDAS started his PhD thesis in January 2024

PhD 2: starting October 2024, more details here below:

Title: "Comparative study of the electronic properties of a-Fe2O3 and BiVO4-based photoanodes by operando STXM-STEM correlative microscopy during the photoelectrolysis reaction"

Thesis director (HDR): Ovidiu ERSEN (IPCMS)  

Thesis co-director: Stefan STANESCU (SOLEIL)

Understanding and subsequently controlling the photoelectrochemical (PEC) activity of materials in contact with aqueous electrolytes during the photoelectrolysis reaction is essential for improving their use in hydrogen production through water dissociation. Photoelectrolysis employs UV-visible light to reduce the external electrical energy required (1.23 V) for splitting the hydrogen from the water molecule in three-electrode electrochemical cells: a photoanode, a metallic cathode (e.g., a Pt wire), and a reference electrode, all immersed in the electrolyte. The current passing through the cell at a constant potential is proportional to the number of electrons involved in the oxidation and reduction reactions (OER and HER, respectively) and thus to the amount of H2 produced during these reactions. Transition metal-based semiconductor oxides are of great interest due to their chemical stability during PEC reactions in aqueous electrolytes. Hematite (α-Fe2O3) is characterized by a bandgap of 2.15 eV, allowing for optimized absorption of the solar spectrum. Hematite exhibits lower PEC activity than other materials due to its short hole diffusion length (2-4 nm) and poor surface kinetics. However, it is abundant, inexpensive, and environmentally friendly, offering the potential for easy integration into a technology following circular economy criteria. One strategy to enhance hematite's PEC activity is to use co-catalysts, such as oxyhydroxides (M-OOH), which directly affect surface kinetics and improve oxidation reaction efficiency. Fundamental understanding of the OER at the interface between hematite-based photoanodes and the aqueous electrolyte can be revealed through a comparative study with another material, BiVO4, characterized by a low electron-hole recombination rate. Unlike hematite, BiVO4 has a hole diffusion length on the order of 100 nm with a bandgap of 2.4 eV. Consequently, BiVO4 exhibits improved conductivity, even though only absorbs light for wavelengths below 510 nm.

The aim of the thesis is to study the physicochemical properties and their evolution at nanoscale using a correlative STXM-STEM microscopy approach during the photoelectrolysis reaction of α-Fe2O3 and BiVO4 photoanodes modified by a co-catalyst. The thesis work will focus on several aspects: i) synthesis of photoanodes using chemical methods on two types of substrates (FTO and glassy carbon); ii) macroscopic photoelectrochemical characterization; iii) characterization of the co-catalyst interface with hematite and BiVO4 using ex situ X-ray spectromicroscopy (STXM and XPEEM) techniques at the HERMES beamline and iv) electron microscopy (STEM); v) fabrication of PEC microcells using nano-lithography, used for both electron and X-ray microscopy; vi) development of a methodology for performing correlative operando STEM-STXM measurements, and vii) operando STXM and STEM characterization using the fabricated microcells and established methodology. Other complementary experimental methods will be used to complete the characterization of the photoanodes: SEM, AFM, KPFM, Raman, XRD, etc.

The doctoral student will acquire diverse and comprehensive skills in advanced material characterization (and data analysis) in general and for energy-related applications in particular. Given the complexity of the study, rigorous scientific methodology is necessary to achieve the set objective. Regular monitoring will be provided to ensure progress and facilitate necessary exchanges for understanding and implementing various steps.

The thesis is co-funded by the ANR OERKOP project (ANR-22-CE50-0033), and the SOLEIL synchrotron. The thesis work will be carried out at the SOLEIL synchrotron, Gif-sur-Yvette, and at the IPCMS, Strasbourg.


Preliminary works and results:

Results dissemination during OERKOP:


2023 : Des matériaux simples et abondants pour une énergie future propre et efficace :




Oral and poster presentations

  • Bilal Meddas , Léon Schmidt, Jean Baptiste Boy, Karine Chaouchi, Stéphanie Blanchandin, Walid Baaziz, Yannick Dappe, Ovidiu Ersen, Ştefan Stănescu, and Dana Stănescu, Efficient Strategies To Optimize Photoelectrochemical Activity of Hematite-based Photoanodes (poster)

ECATALYTIX, X-rays and electronic operando techniques for electrocatalysis – April 3-5, 2024, Strasbourg (France)


  • Ştefan Stănescu, Leon Schmidt , Yannick J. Dappe, Dris Ihiawakrim, W. Baaziz, Ovidiu Ersen, Dana Stănescu, Enhancement of the Solar Water Splitting Efficiency Mediated by Surface Segregation in Ti-doped Hematite Nanorods (oral)

8th International Conference on Catalysis and Chemical Engineering - February 29, 2024 | Boston, MA (USA)


  • Ştefan Stănescu, Yannick J. Dappe, Stéphanie Blanchandin, Karine Chaouchi, Dris Ihiawakrim, Ovidiu Ersen, Dana Stănescu, Band engineering of Earth abundant materials for efficient solar water splitting (oral)

18th SUM2024, 18 & 19 janvier 2024, SOLEIL Synchrotron (France)


  • Léon Schmidt, Walid Baaziz, Dana Stănescu, Ştefan Stănescu, Ovidiu Ersen, Correlative in situ microscopy study of photoanodes used in solar water splitting applications (oral)

The 20th International Microscopy Congress (IMC20), September 10-15, 2023, Busan (Korea)


  • Léon Schmidt, Walid Baaziz, Dana Stănescu, Ştefan Stănescu, Ovidiu Ersen, Correlative in situ microscopy study of photoanodes for solar water splitting (oral)

18ème Colloque de la Société Française des Microscopies, 3 au 7 juillet 2023, Rouen (France)



Scientific preprints and peer-review articles


Internship and PhD thesis



1) Kick-off meetingDate: 20th of April 2023 @SPEC

2) ANR work meeting (video): 25th of January 2024


#3546 - Màj : 27/03/2024


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