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Journée Des Entrants Permanents (nantes Université Et Cnrs)

Séminaire
Dates: Thursday, 07 July 2022 09:30 - 17:00

Place: Amphi IMN Lombarderie

Jeudi 7 juillet à 9h30 - Journée des entrants permanents (Nantes Université et CNRS)

 


09h30 - 10h15

Clement Nicollet
Clément NICOLLET

Relationship between acidity and oxygen exchange kinetics in mixed conducting oxides

In Solid Oxide Fuel Cells, oxygen electrode polarization related to electrochemical reactions at the gas/solid interface is often the dominant flux limiting mechanism. Accumulating surface impurities is known to lead to a reduction in long term durability. On the contrary, surface modification with selected metal oxides can also have a positive effect on the oxygen surface exchange rate1. As there is no clear understanding as to why some elements poison oxide surfaces while others enhance their oxygen exchange kinetics, defining a general descriptor is highly desirable, and is the goal of this work.

In a previous study we used Pr-doped ceria as a model mixed ionic and electronic conductor and infiltrated it with binary oxides of various acidities2.  By comparing the evolution of the surface exchange kinetics with different infiltrated oxides, it was possible to define the acidity of the infiltrated oxide as a descriptor that allows one, on the one hand, to predict what will be the effect of a given oxide on the surface exchange kinetics, and on the other hand to tune the surface exchange coefficient over 7 orders of magnitude with great precision. In this presentation, we will explore the implications of these finding in terms of reactions mechanisms, and how can the acidity/surface exchange relationship be extended to other mixed conductors.

First, the protocol of infiltrating binary oxides to a mixed conductors is applied to perovksites oxides such as (La,Sr)CoO3 and (LaSr)FeO3, and characterized in terms of oxygen exchange kinetics, by conductivity relaxation and impedance spectroscopy. The influence of the infiltrated oxides is then discussed with respect to their acidity, and compared to our previous work on Pr doped Ceria.

Second, the Smith acidity factor3 is calculated for a variety of perovskite oxides, and data collected from the available literature for surface exchange kinetics is analyzed with respect to this new acidity factor. An attempt to use this factor as a complementary tool to describe oxygen surface exchange kinetics is discussed.

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1.    Tsvetkov, N., Lu, Q., Sun, L., Crumlin, E. J. & Yildiz, B. Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface. Nat. Mater. 15, 1010–1016 (2016).
2.    Nicollet, C. et al. Acidity of surface-infiltrated binary oxides as a sensitive descriptor of oxygen exchange kinetics in mixed conducting oxides. Nat Catal 3, 913–920 (2020).
3.    Smith, D. W. An acidity scale for binary oxides. J. Chem. Educ. 64, 480–481 (1987).

 


10h15 - 11h00

ABELLAN Patricia
Patricia ABELLAN

 Titre

Résumé.

 


11h00 - 11h45

Sasaki Shunsuke
Shunsuke SASAKI

The Use of Chalcogen-Chalcogen Bonds as Reactive Buiding Blocks in Solid-State Syntheses

Anions often exhibit distinct reactivity in extended solid-state materials depending on their constituent elements. Group 16 elements, or chalcogens, are well known to catenate in its neutral or anionic form. These chalcogen-chalcogen bonding can be found in various materials, ranging from binary (e.g. Pyrite) and more complex mixed-anion compounds. During the recent 5 years, the speaker has been working on making use of these anionic chalcogen dimers or oligomers as a reactive moiety in solid-state syntheses. The seminar will showcase richness of (de)intercalation chemistry involving chalcogen-chalcogen bonds formation/cleavage, which brought about various metastable compounds.

 


14h45 - 15h30

Steven Renault
Stéven RENAULT

Titre

Résumé.

 


15h30 - 16h15

CLAVEAU Yann 
Yann CLAVEAU

Du transport électronique au transport ionique, parcours d’un routier de la matière condensée.

Soyez les bienvenu⋅e⋅s en Théorie, ce pays où tout se passe bien. À travers une thématique passée et mon projet de recherche actuel, nous allons voir que la modélisation en physique, c’est fantastique.

Le formalisme des fonctions de Green hors équilibre de Keldysh permettent de décrire le transport électronique dans des dispositifs (nano-)optoélectroniques avec une étonnante précision tandis qu’à une autre échelle, la dynamique moléculaire est un véritable nanoscope qui permet de comprendre la dynamique des liquides ioniques confinés.

From electronic to ionic transport, story of a trucker of condensed matter modelling.

Welcome in Theory, this wonderful land in which everything is fine. With a previous thematic and my current research project, we will see that physics modelling is fantastic.

Keldysh non-equilibrium Green-function formalism allows to describe electronic transport in (nano-)optoelectronic devices with astonishing precision, while at another scale, molecular dynamics is a veritable nanoscope which makes it possible to understand the dynamics of confined ionic-liquids.

 


 

16h15 - 17h00

BARBE Jeremy 
Jérémy BARBE

Couches minces pour l’énergie : des cellules solaires à pérovskite aux micro-supercondensateurs

Ce séminaire sera l’occasion de présenter quelques-unes de mes activités de recherche passées, et notamment mes travaux sur les propriétés des cellules solaires à pérovskite et organiques soumises à des conditions de test inhabituelles, sous éclairage artificielle d’une part, et en environnement spatial d’autre part. Je présenterai ensuite mon projet de recherche à l’IMN qui porte sur l’élaboration par procédés plasma de couches minces pour les micro-supercondensateurs, illustré par quelques résultats obtenus au cours de cette première année.

Thin films for energy applications: from perovskite solar cells to micro-supercapacitors

In this presentation, I will describe some of my previous research works on perovskite and organic solar cells measured in unusual testing conditions, on the one hand under artificial lighting and, on the other hand in space environment. Then, I will present my research project in IMN which deals with the elaboration of thin films by plasma processes for energy storage applications such as micro-supercapacitors, illustrated by recent results obtained during this first year.

 

 

 

All Dates


  • Thursday, 07 July 2022 09:30 - 17:00
 
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