Raphaël Chattot
Centre national de la recherche scientifique
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Featured researches published by Raphaël Chattot.
Chemcatchem | 2017
Olivier Le Bacq; A. Pasturel; Raphaël Chattot; Bruno A. F. Previdello; Jaysen Nelayah; Tristan Asset; Laetitia Dubau; Frédéric Maillard
We present a joint experimental and density functional theory (DFT) study on the effect of atomic vacancies on the restructuring of platinum—transition metal alloy nanocatalysts and the associated changes in electrocatalytic activity. Atomic vacancies were introduced into slabs composed of pure Pt monolayers, and the structures were relaxed using the Vienna ab initio simulation package code. Effects of i) the concentration and ii) the spatial distribution of atomic vacancies in the slabs on surface and bulk restructuring were investigated. Highly disordered nanostructures featuring large variations of the in‐plane and out‐of‐plane nearest‐neighbour distances around the mean were observed upon relaxation. These findings were confirmed experimentally by using hollow PtNi/C nanoparticles synthesized by a combination of galvanic replacement and the nanoscale Kirkendall effect (a vacancy‐mediated interdiffusion mechanism). The experimental results also show that hollow PtNi/C nanoparticles feature a combination of oxophilic and oxophobic catalytic sites on their surface and are thus highly active both for electrochemical oxidation and reduction reactions.
Nature Materials | 2018
Raphaël Chattot; Olivier Le Bacq; Vera Beermann; Stefanie Kühl; Juan Herranz; Sebastian Henning; Laura Kühn; Tristan Asset; Laure Guétaz; Gilles Renou; Jakub Drnec; P. Bordet; A. Pasturel; Alexander Eychmüller; Thomas J. Schmidt; Peter Strasser; Laetitia Dubau; Frédéric Maillard
Tuning the surface structure at the atomic level is of primary importance to simultaneously meet the electrocatalytic performance and stability criteria required for the development of low-temperature proton-exchange membrane fuel cells (PEMFCs). However, transposing the knowledge acquired on extended, model surfaces to practical nanomaterials remains highly challenging. Here, we propose ‘surface distortion’ as a novel structural descriptor, which is able to reconciliate and unify seemingly opposing notions and contradictory experimental observations in regards to the electrocatalytic oxygen reduction reaction (ORR) reactivity. Beyond its unifying character, we show that surface distortion is pivotal to rationalize the electrocatalytic properties of state-of-the-art of PtNi/C nanocatalysts with distinct atomic composition, size, shape and degree of surface defectiveness under a simulated PEMFC cathode environment. Our study brings fundamental and practical insights into the role of surface defects in electrocatalysis and highlights strategies to design more durable ORR nanocatalysts.Tuning surface structure is key for electrocatalytic performance and stability of proton-exchange membrane fuel cells. Surface distortion as a structural descriptor can help to clarify the role of surface defects and to design enhanced nanocatalysts.
ChemPhysChem | 2018
Tristan Asset; Raphaël Chattot; Marie Fontana; Benjamin Mercier-Guyon; Nathalie Job; Laetitia Dubau; Frédéric Maillard
Due to their interesting electrocatalytic properties for the oxygen reduction reaction (ORR), hollow Pt-alloy nanoparticles (NPs) supported on high-surface-area carbon attract growing interest. However, the suitable synthesis methods and associated mechanisms of formation, the reasons for their enhanced specific activity for the ORR, and the nature of adequate alloying elements and carbon supports for this type of nanocatalysts remain open questions. This Review aims at shedding light on these topics with a special emphasis on hollow PtNi NPs supported onto Vulcan C (PtNi/C). We first show how hollow Pt-alloy/C NPs can be synthesized by a mechanism involving galvanic replacement and the nanoscale Kirkendall effect. Nickel, cobalt, copper, zinc, and iron (Ni, Co, Cu, Zn, and Fe, respectively) were tested for the formation of Pt-alloy/C hollow nanostructures. Our results indicate that metals with standard potential -0.4<E<0.4 V (vs. the normal hydrogen electrode) and propensity to spontaneously form metal borides in the presence of sodium borohydride are adequate sacrificial templates. As they lead to smaller hollow Pt-alloy/C NPs, mesoporous carbon supports are also best suited for this type of synthesis. A comparison of the electrocatalytic activity towards the ORR or the electrooxidation of a COads monolayer, methanol or ethanol of hollow and solid Pt-alloy/C NPs underlines the pivotal role of the structural disorder of the metal lattice, and is supported by ab initio calculations. As evidenced by accelerated stress tests simulating proton-exchange membrane fuel cell cathode operating conditions, the beneficial effect of structural disorder is maintained on the long term, thereby bringing promises for the synthesis of highly active and robust ORR electrocatalysts.
ACS Catalysis | 2015
Laetitia Dubau; Tristan Asset; Raphaël Chattot; Céline Bonnaud; Victor Vanpeene; Jaysen Neleyah; Frédéric Maillard
ACS Catalysis | 2016
Laetitia Dubau; Jaysen Nelayah; Simona Moldovan; Ovidiu Ersen; P. Bordet; Jakub Drnec; Tristan Asset; Raphaël Chattot; Frédéric Maillard
ACS Catalysis | 2017
Raphaël Chattot; Tristan Asset; P. Bordet; Jakub Drnec; Laetitia Dubau; Frédéric Maillard
Applied Catalysis B-environmental | 2017
Gwenn Cognard; Guillaume Ozouf; Christian Beauger; Grégory Berthomé; David Riassetto; Laetitia Dubau; Raphaël Chattot; Marian Chatenet; Frédéric Maillard
Nano Letters | 2017
Raphaël Chattot; Tristan Asset; Jakub Drnec; P. Bordet; Jaysen Nelayah; Laetitia Dubau; Frédéric Maillard
ACS Catalysis | 2017
Laetitia Dubau; Jaysen Nelayah; Tristan Asset; Raphaël Chattot; Frédéric Maillard
Journal of Membrane Science | 2014
Zhuoxiang Zhang; Raphaël Chattot; Lukas Bonorand; Kaewta Jetsrisuparb; Yves Buchmüller; Alexander Wokaun; Lorenz Gubler