Strengthening the Connection between Science,Society and Environment to Develop Future French and European Bioeconomies: Cutting-Edge Research of VAALBIO Team at UCCS

The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass.     

Precision and control in polymer synthesis why it's important and some recent examples of how to do it

This paper discusses some of the reasons why precision and control in polymer synthesis is of importance. By way of illustration it describes in outline recent results from the authors' laboratories in three areas. Namely; the controlled syntheses of poly(arylene vinylene)s and the influence of cis/trans vinylene content on luminescence in such polymers; the living polymerisation of highly functionalised polymers in water and the regulation of the crystallisation of calcium carbonate from water by the resultant well-defined water soluble polymers; and a simple route to hyperbranched polymers and the influence of the structure and topology of the products on solution properties. In each case the influence of control of architecture on properties will be discussed.     

Synthesis of TiO2 nanoparticles on the Au(111) surface

The growth of titanium oxide nanoparticles on reconstructed Au(111) was investigated by scanning tunneling microscopy and x-ray photoelectron spectroscopy. Ti was deposited by physical-vapor deposition at 300 K. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. The titanium oxide nanoclusters were synthesized by subsequent exposure to O(2) at 300 K. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from 600 to 900 K. At the same time, the Au(111) surface assumes a serrated 110-oriented step-edge morphology suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of the titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to 900 K results in the formation of stoichiometric TiO(2) nanocrystals as judged by the Ti(2p) binding energies measured in the x-ray photoelectron data. The nanodispersed TiO(2) on Au(111) is an ideal system to test the various models proposed for the enhanced catalytic reactivity of supported Au nanoparticles.     

Revisiting the S-Au(111) interaction: static or dynamic?

The Au-S interaction is probably the most intensively studied interaction of Au surfaces with nonmetals, as, for example, it plays an important role in Au ore formation(1) and controls the structure and dynamics of thiol-based self-assembled monolayers (SAMs). Various S-induced surface structures on Au(111) were recently reported for different conditions and predominantly interpreted in terms of a static Au surface. Here, we demonstrate that the Au(111) surface exhibits a very dynamic character upon interaction with adsorbed sulfur: large-scale surface restructuring and incorporation of Au atoms into a growing 2D AuS phase were observed in situ. These results provide new insight into the Au-S surface chemistry.     

Sensitivity of methyl thiolate desulfurization selectivity to reaction temperature and hydroxyl coverage

The adsorption and reaction of methanethiol (CH3SH) and dimethyl disulfide (CH3SSCH3) on Mo(110)-(1 x 6)-O have been studied using temperature-programmed reaction spectroscopy and reflection-absorption infrared spectroscopy over the temperature range of 110-550 K. The S-H bond is broken upon adsorption to form adsorbed OH, water, and methyl thiolate (CH3S-) at low temperature. Water is evolved at 210 and 310 K via molecular desorption and disproportionation of OH, respectively. Some hydroxyl remains on the surface up to 350 K. Methyl thiolate is also formed from CH3SSCH3 on Mo(110)-(1 x 6)-O. Methyl thiolate undergoes C-S cleavage above 300 K, yielding methane and methyl radicals. There is also a minor amount of nonselective decomposition leading to the formation of carbon and hydrogen. Methane production is promoted by adsorbed hydroxyl. As the hydroxyl coverage increases, the yield of methyl radicals relative to methane diminishes. Accordingly, there is more methane produced from methanethiol reaction than from dimethyl disulfide, since S-H dissociation in CH3SH produces OH. The maximum coverage of the thiolate is approximately 0.5 monolayers, based on the amount of sulfur remaining after reaction measured by Auger electron spectroscopy. In contrast to cyclopropylmethanethiol (c-C3H5CH2SH), for which alkyl transfer from sulfur to oxygen is observed, there is no evidence for transfer of the methyl group of methyl thiolate to oxygen on the surface. Specifically, there is no evidence for methoxy (CH3O-) in infrared spectroscopy or temperature-programmed reaction experiments.