Christophe Coutanceau - Academia.edu (original) (raw)

Papers by Christophe Coutanceau

Langmuir, Oct 30, 2023

We report on the electrochemical behavior and shape evolution of Pd nanocubes (Pd NCs) and Pd 3 n... more We report on the electrochemical behavior and shape evolution of Pd nanocubes (Pd NCs) and Pd 3 nanooctahedrons (Pd NOs) with an average size of 9.8 nm and 6.9 nm, respectively, in aqueous alkaline medium in the potential range of the underpotential deposition of H (UPD H) and H 5 absorption. While the Pd NCs and Pd NOs remain stable in the potential region of the UPD H, H 6 absorption and desorption induce structural changes to the Pd NPs, as indicated by the results of 7 electrochemical measurements and identical-location transmission electron microscopy (IL-TEM) 8 analyses. Because both Pd NCs and Pd NOs are known to be stable in the potential region of H 9 absorption and desorption in acidic medium and maintain their structure, the irreversible structural 10 changes are attributed to their interfacial interaction with the aqueous alkaline medium. In the 11 alkaline medium, the nanoparticle surface/electrolyte interfacial structure plays an essential role 12 in the mechanism of H desorption that is observed at higher potentials than in the acidic medium. 13 Hydrogen desorption is substantially hindered due to the structure of water network adjacent to 14 the Pd nanoparticles or the interaction between hydrated cations and adsorbed OH on the 15 nanoparticle surface, resulting in the trapping of a small amount of H (incomplete H desorption). 16 It is proposed that H trapping and associated structural strain lead to deformation of the Pd 17 nanoparticles and loss of their initial structure.

Electrochemistry Communications, Nov 1, 2014

Shape-controlled nanoparticles (NPs) are viewed as electrocatalysts of choice for fuel cell appli... more Shape-controlled nanoparticles (NPs) are viewed as electrocatalysts of choice for fuel cell applications. However, to date very few studies focus on the persistence of the controlled shape upon operation. Herein, the degradation of cubic palladium NPs is studied in alkaline media using Identical Location Transmission Electron Microscopy (ILTEM) and electrochemical measurements; this work brings evidence that the cubic shape is rapidly destroyed in certain conditions.

Applied Catalysis B-environmental, Nov 1, 2011

Effects toward electrocatalytic activity for glycerol oxidation of the modification of carbon sup... more Effects toward electrocatalytic activity for glycerol oxidation of the modification of carbon supported Pd and Pt-based nanomaterials by bismuth were evaluated in alkaline medium. Pd/C, Pd 0.9 Bi 0.1 /C, Pt/C, Pt 0.9 Bi 0.1 /C and Pd 0.45 Pt 0.45 Bi 0.1 /C catalysts were synthesized by a colloidal route, and physical and electrochemical methods were used to characterize the structure and the surface of the catalysts (TEM, HRTEM, EDX, XRD, ICP-OES and XPS). It was shown that only a few amount of bismuth was deposited on the Pt and/or Pd surface, and that no alloy was formed between bismuth and the other metals. The onset potential of glycerol oxidation is ca. 0.15 V lower on Pt/C than on Pd/C. However, Pt-free Pd 0.9 Bi 0.1 /C catalyst presented the same catalytic activity than platinum catalyst. The Pt 0.9 Bi 0.1 /C led reaching a higher catalytic activity by shifting the oxidation onset potential by ca. 0.2 V toward lower potentials compared with the Pt/C catalyst. But, the replacing of half of the platinum atoms by palladium atoms in the Pd 0.45 Pt 0.45 Bi 0.1 /C material allowed achieving the same catalytic activity as with Pt 0.9 Bi 0.1 /C. Electrochemical experiments combined with in situ infrared spectroscopy measurements have shown that glycerol electrooxidation mechanism is independent on the catalyst, but dependent on the electrode potential. Chronoamperometry experiments combined with HPLC measurements showed that the main reaction products were glycerate, dihydroxyacetone and tartronate at low potentials, and that the increase of the electrode potential led to the formation of mesoxalate. For potential higher than 0.8 V vs RHE, the CC bond cleavage occurred and oxalate and formiate were detected.

Meeting abstracts, 2011

not Available.

Electrocatalysis, Mar 30, 2012

ABSTRACT The understanding of CO oxidation on platinum catalysts is a key point in several low-te... more ABSTRACT The understanding of CO oxidation on platinum catalysts is a key point in several low-temperature fuel cell technologies: direct-alcohol fuel cells or proton-exchange membrane fuel cell fed with reformate hydrogen, for example. For this purpose, studies were carried out on different platinum surfaces, from single crystals surfaces with a well-defined orientation to platinum nanoparticle polyoriented surfaces. This article presents the CO electrooxidation on surfaces of Pt single crystals and Pt nanoparticles with different orientations and size ranges. The study of CO oxidation was completed with in situ reflectance spectroscopy coupled to electrochemical methods. The confrontation of CO oxidation behaviours observed on electrodes with oriented surfaces at macroscopic and nanoscopic size ranges allowed establishing a correlation between the surface structure and the CO oxidation voltammetric features.

Applied Catalysis B-environmental, Dec 1, 2017

Effect of the annealing atmosphere on the electrochemical properties of RuO2 nano-oxides synthesi... more Effect of the annealing atmosphere on the electrochemical properties of RuO2 nano-oxides synthesized by the Instant Method, Applied Catalysis B,

Journal of Power Sources, 2008

Polyoxymethylenedimethylethers CH 3 O (CH 2 O) n CH 3 with n varying from 1 to 4 are studied for ... more Polyoxymethylenedimethylethers CH 3 O (CH 2 O) n CH 3 with n varying from 1 to 4 are studied for a possible application as fuels in PEMFC. Cyclic voltammetry is performed at Pt, Pt/Ru(50/50), Pt/Ru(80/20) electrodes in acidic medium to evaluate their electroactivity. Electrical performance of the fuels are evaluated in a 5 cm 2 direct fuel cell for different temperatures and pressures with Pt and Pt/Ru(50/50) catalysts at the anode and Pt at the cathode. The determination of the reaction products is performed in a 25 cm 2 direct fuel cell under working conditions at constant current for 3 h. Preliminary results are very promising regarding achieved power densities. Results pointed out the important role of hydrolysis of these compounds into methanol and formaldehyde in electroreactivity. It is probable that the cell performances are due to the oxidation of the products coming from hydrolysis rather than to direct oxidation of the polyoxymethylenedimethylethers. Polyoxymethylenedimethylethers appear to be attractive candidates as alternative to methanol, which moreover is a toxic (neurotoxin) molecule.

Wiley Interdisciplinary Reviews: Energy and Environment, Jan 15, 2016

In the emerging hydrogen economy, one of the major objectives is the production of electricity us... more In the emerging hydrogen economy, one of the major objectives is the production of electricity using fuel cells, particularly proton exchange membrane fuel cells (PEMFC). In this perspective, high purity hydrogen is needed. Hydrogen is currently mainly produced from fossil fuels (natural gas, oil, and coal) by energy‐consuming and environmentally unfriendly industrial processes that also involve complicated clean up steps for the removal of carbon monoxide and carbon dioxide. Water electrolysis (particularly the proton exchange membrane electrolysis technology, which allows higher efficiency than alkaline technology) appears to be a good candidate for the production of clean hydrogen. The use of renewable primary energy sources, such as wind, solar, tidal, etc., makes this technology greener. However, the low kinetics of water oxidation, which implies high cell voltage (i.e. high energy consumption) even when using noble metal‐based catalysts (Pt, Ru, Ir), makes this technology expensive. Biosourced alcohols can be interesting alternatives as hydrogen carriers in an electrolysis cell; their reversible oxidation potentials are much lower than that of water, ca 0.1 V versus SHE (standard hydrogen electrode) against 1.23 V versus SHE, so that the cell voltages for hydrogen production are lower (and so is the energy consumption). However, the low kinetics of alcohol oxidation in acidic media requires high Pt‐based catalyst loadings at the anode. Direct alcohol alkaline electrolysis cells can be operated with low Pt loading and even non‐noble metals. In the case of glycerol, generation of hydrogen at the cathode can be performed simultaneously with the formation of value‐added products at the anode for a more profit‐making process. WIREs Energy Environ 2016, 5:388–400. doi: 10.1002/wene.193This article is categorized under: Bioenergy > Science and Materials Fuel Cells and Hydrogen > Science and Materials Energy Efficiency > Science and Materials

Journal of Physical Chemistry C, Jul 1, 2009

ABSTRACT

Journal of Electroanalytical Chemistry, Apr 1, 2005

The electrocatalytic performance of iron phthalocyanine, FePc, dispersed on a high surface area c... more The electrocatalytic performance of iron phthalocyanine, FePc, dispersed on a high surface area carbon substrate (Vulcan XC 72) was investigated in acid medium. The polarisation curve of oxygen reduction on the FePc/C catalyst in a methanol containing O2-saturated electrolyte was compared to that obtained on a platinum catalyst. Results showed clearly that FePc/C catalyst is totally insensitive to the presence

Meeting abstracts, 2017

The electrochemical conversion of biosourced compounds such as alcohols/polyols and saccharides g... more The electrochemical conversion of biosourced compounds such as alcohols/polyols and saccharides gains more and more attention for their potency hydrogen and added-value-chemical cogeneration [1–4] from an energy efficient method compatible with several green chemistry principles. Alcohols and polyols can be produced from biomass (and are a by-product of biofuel industry in the case of glycerol) and represent an interesting challenge for the production of platform molecules for further chemical transformations into polymers, surfactants, etc. The main challenges are then reaching a high activity and controlling the selectivity of the anode. These challenges can be addressed by the reaction medium and the catalyst design with modification of catalytic metals (generally platinum group metal) with p-group and d-group metals to improve the activity and tune the selectivity towards desired reaction products [1,4-7]. The use of saccharide for hydrogen and value-added chemical cogeneration would represent a convenient way of introducing biosourced molecules in the hydrogen and platform molecules production chain. Indeed, a large part of cellulosic biomass which is not devoted to food industry is composed of saccharide derivatives. The production of saccharide from these resources is then less demanding in terms of energy and chemical steps than alcohol / polyol production. Furthermore, the oxidation of saccharide in alkaline medium under conditions similar to that of an electro-reforming cell [8] leads to the formation of carboxylic acids very similar to those produced from alcohol / polyol electro-reforming and to longer carboxylic acids. However, while the oxidation of saccharide such as glucose and xylose starts at low potential, it remains difficult to reach high current densities compatible with an industrial process and the reactant turnover has to be improved. Finally, the conversion of these compounds is performed with co-production of clean hydrogen on the cathode, at low cell voltage (typically less than 1 V) compared to water electrolysis [2–4,7]. Acknowledgement: The research leading to these results has received funding from the French National Research Agency (ANR) under grant agreement N° ANR-16-CE29-0007-01 (ECO-PLAN project) [1] M. Simões, S. Baranton, C. Coutanceau, Electrochemical Valorisation of Glycerol, ChemSusChem, 5 (2012) 2106–2124 [2] Y.X. Chen , A. Lavacchi, H.A. Miller, M. Bevilacqua, J. Filippi, M. Innocenti, A. Marchionni, W. Oberhauser, L. Wang, F. Vizza, Nanotechnology makes biomass electrolysis more energy efficient than water electrolysis, Nature Commun., 5 (2014) 4036 [3] C. Lamy, T. Jaubert, S. Baranton, C. Coutanceau, Clean hydrogen generation through the electrocatalytic oxidation of ethanol in a proton exchange membrane electrolysis cell (PEMEC). Effect of the nature and structure of the catalytic anode. J Power Sources, 245 (2014) 927–936 [4] C. Coutanceau, S. Baranton, Electrochemical conversion of alcohols for hydrogen production: a short overview, WIRE Energy and Environment, (2016) 388-400 [5] A. Zalineeva, A. Serov, M. Padilla, U. Martinez, K. Artyushkova, S. Baranton, C. Coutanceau, P.B. Atanassov, Self-Supported PdxBi Catalysts for the Electrooxidation of Glycerol in Alkaline Media, J. Am. Chem. Soc., 136 (2014) 3937−3945 [6] A. Zalineeva, A. Serov, M. Padilla, U. Martinez, K. Artyushkova, S. Baranton, C. Coutanceau, P.B. Atanassov, Glycerol electrooxidation on self-supported Pd1Snxnanoparticules, Appl. Catal. B: Environ., 176 (2015) 429–435 [7] J. Gonzalez-Cobos, S. Baranton, C. Coutanceau, Development of Bismuth-Modified PtPd Nanocatalysts for the Electrochemical Reforming of Polyols into Hydrogen and Value-Added Chemicals, ChemElectroChem, 3 (2016) 1694–1704 [8] A.T. Governo, L. Proença, P. Parpot, M.I.S. Lopes, I.T.E. Fonseca, Electro-oxidation of d-xylose on platinum and gold electrodes in alkaline medium, Electrochim. Acta, 49 (2004) 1535–1545

Electrocatalysis, Jul 9, 2018

Platinum nanoparticles supported on a carbon support (Pt-NPs/C) were synthesized by a polyol meth... more Platinum nanoparticles supported on a carbon support (Pt-NPs/C) were synthesized by a polyol method and modified by grafting of different non-fluorinated and fluorinated proton conducting polymers. In the case of fluorinated polymers, the sulfonyl functions were attached either directly or through spacers (-O-PSA and-S-PSA) to the tetrafuorovynilic groups. Results in three-electrode electrochemical cell showed that the nature and structure of the grafted proton conducting polymer influenced mass transport in the catalytic film towards the oxygen reduction active sites, the limiting current density in the catalytic film decreasing from ca. 97 mA cm-2 for Pt-NPs/C to ca. 80 mA cm-2 for Pt-NPs-(PSSA)/C and less than 60 mA cm-2 for Pt-NPs-(PTFV-O-PSA)/C and Pt-NPs-(PTFV-S-PSA)/C. This influence was directly linked to the hydrophobic character of the polymers. The importance of the spacer on the electrochemically active surface area (ECSA), kinetic current density (j k) and mass activity (MA) at 0.9 V was pointed out. The j k at 0.9 V vs. RHE increased from 2.8 mA cm-2 to 3.6 mA cm-2 for the nanocomposite catalysts without spacer and with a-O-PSA spacer, respectively. However, the best performance was obtained with Pt-NPs-(PSSA)/C with j k = 8.6 mA cm-2 (Pt-NPs/C leading to 4.6 mA cm-2). Fuel cell tests also showed the influence of the grafted polymer on the water management in cathodes. Maximum power density of ca. 1 W cm-2 at ca.

Elsevier eBooks, 2018

In this section, alternative systems to water electrolysis for electrochemical hydrogen synthesis... more In this section, alternative systems to water electrolysis for electrochemical hydrogen synthesis such as conventional alcohols (methanol, ethanol), biosourced polyols (ethylene glycol, glycerol), and saccharides from nonedible biomass are discussed. The importance of the nature, composition, and structure of catalysts and of the reaction medium on the activity and selectivity is presented. It is shown that the control of the electrode potential, catalyst composition, and reaction medium allows tuning the selectivity and increasing the activity, and further to produce simultaneously high purity hydrogen at the cathode of an electrolysis cell and value-added compounds with high selectivity at the anode of the electrolysis cell.

Nanoscale advances, 2021

Platinum (Pt), platinum-bismuth (PtBi), platinum-copper (PtCu) and platinum-bismuth-copper (PtCuB... more Platinum (Pt), platinum-bismuth (PtBi), platinum-copper (PtCu) and platinum-bismuth-copper (PtCuBi) clusters were grown in a gas aggregation source (GAS) equipped with three in-plane plasma magnetrons located in a single region of the gas aggregation zone. The X-ray diffraction results have shown that PtCu clusters form alloys as the decrease of the lattice parameter occurs when the Cu atomic content increases. PtBi clusters do not form alloys, but the presence of secondary Bi oxide phases was detected. Scanning transmission electron microscope mapping images revealed that simultaneously adding Bi and Cu to Pt leads to PtCu alloyed clusters decorated with Bi or CuBi species on the surface. The electrochemical results indicated that the shell might be composed of a metastable CuBi phase. Electrochemical measurements have shown that the addition of Bi or Cu to the Pt clusters enhances the catalytic activity for glycerol oxidation by decreasing the oxidation onset potential.

Electrocatalysis, Feb 2, 2010

Platinum nanocubes and tetrahedrons/octahedrons were synthesized by different methods using diffe... more Platinum nanocubes and tetrahedrons/octahedrons were synthesized by different methods using different surfactants (tetradecyltrimethylammonium bromide (TTAB) and sodium polyacrylate). Transmission electron microscopy (TEM) investigations show high selectivity in shape and low size dispersion. However, the small nuclei observed at the surface of some nanocubes synthesized using the TTAB method is not yet clarified. The presence of such small particles could be explained by a double nucleation or different growth processes which might occur during synthesis. Electrochemical characterizations indicated that particles exhibited ca. 60% of oriented surface domains. Cyclic voltammetry and adatom adsorption displayed a very good agreement with TEM results.

Electrochimica Acta, Mar 1, 2008

Nanostructured Pt 1−x Bi x /C electrocatalysts (x from 0 to 0.3) are prepared via a microemulsion... more Nanostructured Pt 1−x Bi x /C electrocatalysts (x from 0 to 0.3) are prepared via a microemulsion method. The electroactivity of the catalysts towards oxygen reduction reaction (orr) is investigated. The following order of catalysts for electrochemical activity towards orr is obtained: Pt 0.8 Bi 0.2 /C > Pt 0.9 Bi 0.1 /C > P/C > Pt 0.7 Bi 0.3 /C. RDE and RRDE experiments indicate a four-electron reduction reaction mechanism in the low overpotentials region with all Pt 1−x Bi x /C electrocatalysts, whereas, at higher overpotentials a two-electron mechanism producing hydrogen peroxide co-exists with the four-electron mechanism producing water. Two Tafel slopes are obtained for all catalysts. In the low overpotentials region all Bi-containing catalysts display Tafel slopes close to −60 mV decade −1 , against −80 mV decade −1 for pure platinum. In the high overpotentials region, the Tafel slopes are close to −120 mV decade −1 , except for the Pt 0.7 Bi 0.3 /C for which a Tafel slope close to −100 mV decade −1 is observed. Results are explained in terms of protection of platinum surface from oxidation by the presence of more easily oxidizable species, leading to shift the reduction wave of 20-30 mV towards higher potentials, while the platinum surface coverage by bismuth oxides species leads to decrease the accessible platinum sites and further the orr kinetics. At last, the higher tolerance of a Pt 0.8 Bi 0.2 /C catalyst to the presence of ethylene glycol is demonstrate, as well as its higher performance as cathode catalyst under direct ethylene glycol solid alkaline membrane fuel cell working conditions.

ECS transactions, Oct 4, 2011

Program and Proceedings Book, 2006

ECS Meeting Abstracts, 2020

Keywords: electrocatalytic oxidation, glucose, methylglucoside, cellobiose, trehalose, electrolys... more Keywords: electrocatalytic oxidation, glucose, methylglucoside, cellobiose, trehalose, electrolysis, platinum, bismuth, selectivity Different catalysts (Pt/C, Pt9Bi1/C, Pt9Sn1/C, Pt7Ni3/C, Pt7Sn3/C and Pd3Au7/C) have been synthesized by a “water in oil” micro-emulsion method with nominal metal loading of 40 wt% and further characterised by physicochemical methods: thermogravimetric analysis, transmission electron microscopy, X-Ray diffraction, etc., to assess the metal loading, composition and size of nanoparticles. Linear scan voltammograms (Fig.1) have been performed to study the electrocatalytic behaviour of the catalysts towards electro-oxidation of glucose, methylglucoside, cellobiose and trehalose in 0.1 M NaOH as background electrolyte at 0.05 V s-1 scan rate. Pt9Bi1/C, most active one, leads to the lowest onset potentials of ca. 0.050 V, 0.100 V, 0.050 V and 0.200 V vs RHE for glucose, methylglucoside, cellobiose and trehalose oxidation respectively. To further gain an insig...