DS0205 -

In-Situ ElectroChemistry applied to Energy-related catalysis – InSiChem

Multi-scale in situ study of electrocatalysts for energy conversion

Development and optimisation of an experimental approach based on electron microscopy and X-rays spectroscopy for the in situ and operando analysis of electrocatalysts

Understanding the properties of nanometric metal oxides used as catalysts in electrochemical reactions.

The InSiChem project has been set out to study the catalytic properties of several types of materials used for electrocatalysis, especially mixed oxides and metal-boron compounds, with the aim of improving the understanding of their structures and properties to promote the use of these materials in energy applications. To achieve this goal, the stability of these materials and their morphological, structural, chemical and electronic evolutions during electrocatalysis have been studied in situ in real time. We have particularly focused on water reduction and oxidation reactions involved in fuel cells and water electrolyzers. The information thus obtained allowed us to modify the synthesis pathways of these materials for a better control of their stoichiometry, morphology or even shaping within the working electrodes. These modifications subsequently led to improving their performance in terms of catalytic efficiency and stability over time.

The experimental approach of in situ analysis that we have proposed for studying the actual structure of electrocatalytic materials under operating condition, consists in combining synchrotron-based X-ray absorption spectroscopy with transmission electron microscopy. The materials placed in electrochemical cells are observed at the macroscopic scale through X-ray spectroscopy and at the nanoscale through electron microscopy. This study of electrocatalysts is the first use in France of the combination of environmental electron microscopy analysis coupled with in situ electrochemical measurements. Likewise, some X-ray spectroscopic approaches that we have used have been developed specifically for electrocatalysis. Environmental electron microscopy can detect phase transition at the scale of a single particle, while X-ray absorption spectroscopy can monitor changes in the oxidation, spin or protonation state of metals and their ligands over a collection of nanoparticles.

Our in situ studies of electrocatalytic reactions are linked to energy issues such as the electrolysis of water for H2 production and the reduction of dioxygen in fuel cells. It has improved our knowledge of the nanoparticles studied and of the techniques developped. We have made three important steps forward: (1) set up of the methodology for worldwide dissemination targeting various materials; (2) discovery of an unexpected phenomenon consisting in the almost complete amorphization of cobalt oxide spinel nanoparticles during water oxidation catalysis; (3) indepth modification of the mechanism of dioxygen reduction on multicationic perovskite oxide electrocatalysts, depending on the materials composition.

Thanks to the direct insight obtained during the project into the structural transformations of electrocatalysts in operating condition, new perspectives can be now considered for optimizing their synthesis as well as for exploring new materials configurations, in order to improve their subsequent properties. Some new instrumental developments can be also considered, such as for example the design of an electrochemical cell compatible with ultra-vacuum conditions in order to be able to measure the K edges of light elements on a low-energy light synchrotron line and allow the study of these elements which are generally present in electrocatalysts in association with heavy elements. In a more general context, several projects, ANR or others, including members of the consortium have been recently submitted and are dedicated to the development of other new approaches for the in situ characterization of nanomaterials under operating conditions, based on the combination of electron microscopy with synchrotron techniques, which once again illustrates the relevance of this methodology for the study of functional materials.

The consortium has been able to capitalize on the obtained results by the publication of several articles in high-impact scientific journals (ACS Nano, J. Phys. Chem. Letters, one more manuscript submitted). The results obtained have been the subject of two doctoral dissertations and have been presented in a large number of international conferences and seminars.

This project aims at developing an original methodology for the multiscale in-situ investigation of electrocatalytic materials. The in-situ approach consists in combining synchrotron-based X-ray spectroscopic techniques with transmission electron microscopy to study the actual structure of catalytic materials under operating conditions. The materials will be studied in liquid electrochemical cells at the macroscopic scale using X-ray spectroscopic techniques and at the nanometric scale using electron microscopy. Until now, the electrochemical TEM technology has only been successfully applied to the study of energy storage in Li-ion batteries. Similarly, the X-ray spectroscopic techniques that we will be using have only been applied in very few examples for the study of electrocatalytic reactions. The combination of these two techniques for the study of electrochemical reactions pertaining to energy-related issues such as water-splitting or dioxygen reduction will undoubtedly strengthen our knowledge on these systems. The developed approach should lead on the mid-term to significant breakthrough in the field.

We will explore several systems of interest: manganese and cobalt based perovskites, which have an electrocatalytic activity for oxygen evolution reaction and oxygen reduction reaction, respectively, and metal phosphides and borides, which are active for the reduction of protons into hydrogen. Stability, morphology as well as structural and electronic changes in these materials will be studied in situ during electrochemical processes. Electron microscopy will provide information on possible corrosion effects or phase transitions at the scale of a single particle, while X-ray spectroscopy will provide clues on the oxidation, spin and protonation state of the metals and their ligands. We will measure such data under various experimental conditions such as pH or electrochemical potential and correlate them with the electrochemical data in order to get insight into the reaction mechanism. The information we will gather from these in situ experiments will guide us to modify the synthesis routes to focus on the morphology, stoichiometry or deposition procedure on the working electrodes, so as to improve the performance of these materials in terms of electrocatalytic efficiency and stability over time.

Project coordinator

Monsieur Ovidiu ERSEN (Instittut de Physique et Chimie des Matériaux de Strasbourg)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

SOLEIL Synchrotron SOLEIL
LCMCP Laboratoire Chimie de la Matière Condensée de Paris
IPCMS Instittut de Physique et Chimie des Matériaux de Strasbourg

Help of the ANR 501,585 euros
Beginning and duration of the scientific project: September 2016 - 42 Months

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