Eric Genty

Gold catalysts in environmental remediation and water-gas shift technologies

This review presents studies and investigations of the use of gold catalysts in environmental applications, from the oxidation of CO and volatile organic compounds (VOCs) in environmental technologies to the production of hydrogen, a non-polluting energy source, in the water-gas shift (WGS) reaction. It summarizes a variety of results, from the discovery made by Haruta et al. about the catalytic behaviour of gold in CO oxidation, to the use of gold-based catalysts in environmental remediation, by the catalytic removal of different types of VOC using a wide variety of oxide supports and finally to the use of this highly active noble metal in WGS applications. It also discusses gold loading methods, comparing them in terms of simplicity, efficiency and the resultant particle size and dispersion of Au over various supports. The application of different types of supporting materials is also presented, with a critical discussion of the parameters affecting the choice and use of such materials, i.e. how the support interacts with gold particles and with pollutant molecules along with the advantages a support offers to VOC oxidation and WGS reactions. It ends by highlighting the potential of gold catalyts in the future.

Usefulness of toxicological validation of VOCs catalytic degradation by air-liquid interface exposure system

Abstract Toluene is one of the most used Volatile Organic Compounds (VOCs) in the industry despite its major health impacts. Catalytic oxidation represents an efficient remediation technique in order to reduce its emission directly at the source, but it can release by‐products. To complete the classical performance assessment using dedicated analytical chemistry methods, we propose to perform an untargeted toxicological validation on two efficient catalysts. Using biological system allows integrating synergy and antagonism in toxic effects of emitted VOCs and by‐products, often described in case of multi‐exposure condition. Catalysts Pd/&agr;‐Al2O3 and Pd/&ggr;‐Al2O3 developed for the oxidation of toluene were both coupled to a Vitrocell® Air‐Liquid Interface (ALI) system, for exposure of human A549 lung cells during 1 h to toluene or to catalysts exhaust before quantification of xenobiotics metabolizing enzymes. This study validated initially the Vitrocell® as an innovative, direct and dynamic model of ALI exposure in the assessment of the performances of new catalysts, showing the presence of chemically undetected by‐products. The comparison of the two catalysts showed then that fewer organic compounds metabolizing genes were induced by Pd/&ggr;‐Al2O3 in comparison to Pd/&agr;‐Al2O3, suggesting that Pd/&ggr;‐Al2O3 is more efficient for toluene total oxidation from a toxicological point of view. Graphical abstract Symbol. No caption available. HighlightsCatalytic oxidation is an efficient remediation technique of industrial VOC emissionsCatalyst performance is generally assessed measuring VOC conversion or CO2 emission, but not the formation of by‐products.Untargeted toxicological validation of catalyst by coupling it to an Air‐Liquid Interface exposure system.Using biological system allows integrating synergy and antagonism in toxic effects of emitted VOCs and by‐products.CYP1A1 induction in exposed A549 cells showed the formation of PAHs undetected by chemical methods.

Chiral adsorption studied by field emission techniques: the case of alanine on platinum

Chirality at surfaces has become an active research area targeting possible applications of enantioselective separation or detection. Here, we propose a promising route for obtaining fundamental understanding of the enantiospecific interaction of chiral molecules on metal surfaces using field emission techniques, i.e. field ion microscopy (FIM) and field electron microscopy (FEM). These techniques have been chosen for their particular advantages in exposing a wide range of structurally different facets in one atomically resolved picture. This diversity allows the study of interactions between a chemical species and a number of facets during the adsorption process on the same sample. In the present study, we focused on the adsorption of alanine on platinum surfaces modelled as sharp tips and imaged by FIM and FEM. Our results show a clear preference of the alanine to adsorb on chiral facets. Although the 20 A resolution of the FEM does not allow the edges of the facets of interest to be unraveled, the net images after exposure to one enantiomer of alanine show the occurrence of enantioselective adsorption over the sector of the same chiral symmetry. The results show that L-alanine has a strong tendency to adsorb onto R facets. Conversely, D-alanine adsorbs onto S facets.

Nanoscale Imaging of Subsurface Oxygen Formation on Rhodium Catalysts

During a catalytic process, a catalyst may undergo changes of its structure or morphology, as well as modifications of its local composition, which is due to oxidation/reduction processes, surface segregation, or even the presence of subsurface species [1]. All these modifications may affect the activity and the selectivity of the catalyst and contribute to the ageing of the catalyst. To develop catalysts with improved efficiency, a fundamental understanding of the catalytic process is needed. The shape of the nanoparticle, its size, its local chemical composition and the synergistic influences of these features on the catalytic activity must be determined, down to the molecular level, to unravel the details of this reaction. Such studies gain significance if they are performed during the ongoing process so as to highlight transient behaviors that cannot be observed before and after reactions.