Développement de systèmes électrocatalytiques pour la conversion du CO2 en produits chimiques

Cette thèse s'inscrit dans le domaine de la photosynthèse artificielle proposant de convertir de l'énergie lumineuse ou électrique pour convertir le CO2 en produits chimiques énergétiquement denses. Y sont notamment exposés les développements de systèmes hétérogènes à base d'alliages métalliques permettant de catalyser la conversion du CO2 en monoxyde de carbone, syngas, mais aussi éthylène et éthanol.This thesis lies in the field of artificial photosythesis that centers around the conversion of CO2 into chemical fuels using electricity or sun power. This works report the develoment of heterogeneous metal-alloy-based systems for the conversion of CO2 into carbon monoxide, syngas and also, ethylene or ethanol

Epstein–Barr Virus-Associated T- and NK-Cell Lymphoproliferative Diseases: A Review of Clinical and Pathological Features

Epstein–Barr virus (EBV) is a ubiquitous virus detected in up to 95% of the general population. Most people are asymptomatic, while some may develop a wide range of EBV-associated lymphoproliferative disorders (LPD). Among them, EBV-positive T/NK LPD are uncommon diseases defined by the proliferation of T- or NK-cells infected by EBV. The 2017 World Health Organization (WHO) classification recognizes the following entities characterized by different outcomes: chronic active EBV infection of T- or NK-cell types (cutaneous and systemic forms), systemic EBV-positive T-cell lymphoma of childhood, EBV-positive aggressive NK-cell leukemia, extra nodal NK/T-cell lymphoma nasal type, and the new provisional entity known as primary EBV-positive nodal T/NK-cell lymphoma. In addition, EBV associated-hemophagocytic lymphohistiocytosis is part of EBV-positive T/NK LPD, but has not been included in the WHO classification due to its reactive nature. Despite novel insights from high-throughput molecular studies, EBV-positive NK/T-cell LPD diagnoses remain challenging, especially because of their rarity and overlap. Until now, an accurate EBV-positive NK/T LPD diagnosis has been based on its clinical presentation and course correlated with its histological features. This review aims to summarize clinical, pathological and molecular features of EBV-positive T/NK LPD subtypes and to provide an overview of new understandings regarding these rare disorders

Coupling electrocatalytic CO2 reduction with thermocatalysis enables the formation of a lactone monomer

International audienceCarbonylation reactions that generate high-value chemical feedstocks are integral to the formation of many industrially significant compounds. However, these processes require the use of CO, which is invariably derived from fossil-fuelreforming reactions. CO may also be generated through the electroreduction of CO2, but the coupling of these two processes is yet to be considered. Merging electrocatalytic reduction of CO2 to CO with thermocatalytic use of CO would expand the range of the chemicals produced from CO2. This work describes for the first time the development of a system coupling a high-pressure CO2 electrolytic cell containing a bimetallic ZnAg catalyst at the cathode for production of CO with a reactor with a faradaic efficiency of >90 % where high pressure CO is used for carbonylating propylene oxide into β-butyrolactone by thermal catalysis, the latter step having a reaction yield above 80%. While the production of monomers and polymers from CO2 is currently limited to organic carbonates, this strategy opens up the access to lactones from CO2, for the formation of polyesters

Bio-inspired hydrophobicity promotes CO2 reduction on a Cu surface

International audienceThe aqueous electrocatalytic reduction of CO2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multicarbon products (C2/C3), but competing proton reduction to hydrogen is an ever-present drain on selectivity. Here, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained a 56% Faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO2 at the electrode–solution interface and consequently increase CO2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts

Dataset for: Bio-inspired hydrophobicity promotes CO2 reduction on a Cu surface

The aqueous electrocatalytic reduction of CO2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multicarbon products (C2/C3), but competing proton reduction to hydrogen is an ever-present drain on selectivity. Herein, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained a 56% faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO2 at the electrode–solution interface and consequently increase CO2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts

Raw Data suporting article: Oxygenic Photoreactivity in Photosystem II Studied by Rotating Ring Disk Electrochemistry

The data is primarily electrochemical, acquired with the rotating ring disk electrode (RRDE) apparatus, as described in the manuscript. The RRDE technique offers a new approach in PSII studies because it allows for the real-time (∼ms) analysis of reaction pathways without the necessities of high currents (∼nA sensitivity) and bulk product accumulation. Briefly, the data was acquired with a potentiostat in a three or four electrode setup. The raw data files are converted into text. Photocurrent magnitudes are processed from raw data as well. The background dark current is subtracted to extract out photocurrent measurements. Additional experimental details are located in the experimental section at the end of the main text

Zn-Cu Alloy Nanofoams as Efficient Catalysts for the Reduction of CO 2 to Syngas Mixtures with a Potential-Independent H 2 /CO Ratio

International audienceAlloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, we explore the use of such a strategy to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 vs. H + reduction. By varying the Zn:Cu ratio, tailored syngas mixtures were attained with no other gaseous products, which we assign to preferential CO and H2 forming pathways on the alloys. The syngas ratios were also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis to renewable power sources of fluctuating intensity. As such, industrially-relevant syngas ratios were achieved at large currents (-60 mA) for extensive operating times (> 9 h), demonstrating the potential of this strategy for fossil-free fuel production

Oxygenic Photoreactivity in Photosystem II Studied by Rotating Ring Disk Electrochemistry.

Protein film photoelectrochemistry has previously been used to monitor the activity of photosystem II, the water-plastoquinone photooxidoreductase, but the mechanistic information attainable from a three-electrode setup has remained limited. Here we introduce the four-electrode rotating ring disk electrode technique for quantifying light-driven reaction kinetics and mechanistic pathways in real time at the enzyme-electrode interface. This setup allows us to study photochemical H2O oxidation in photosystem II and to gain an in-depth understanding of pathways that generate reactive oxygen species. The results show that photosystem II reacts with O2 through two main pathways that both involve a superoxide intermediate to produce H2O2. The first pathway involves the established chlorophyll triplet-mediated formation of singlet oxygen, which is followed by its reduction to superoxide at the electrode surface. The second pathway is specific for the enzyme/electrode interface: an exposed antenna chlorophyll is sufficiently close to the electrode for rapid injection of an electron to form a highly reducing chlorophyll anion, which reacts with O2 in solution to produce O2•-. Incomplete H2O oxidation does not significantly contribute to reactive oxygen formation in our conditions. The rotating ring disk electrode technique allows the chemical reactivity of photosystem II to be studied electrochemically and opens several avenues for future investigation.Royal Society Newton International Fellowship, ERC Consollidator Grant, BBSRC, EPSRC, French Corps of Bridges, Waters & Forests, VU University Amsterdam, ERC Advanced Investigator grant, EU FP7 project, Academy Professor grant from the Netherlands Royal Academy of Science

Low-cost high-efficiency system for solar-driven conversion of CO2 to hydrocarbons

Conversion of carbon dioxide into hydrocarbons using solar energy is an attractive strategy for storing such a renewable source of energy into the form of chemical energy (a fuel). This can be achieved in a system coupling a photovoltaic (PV) cell to an electrochemical cell (EC) for CO2 reduction. To be beneficial and applicable, such a system should use low-cost and easily processable photovoltaic cells and display minimal energy losses associated with the catalysts at the anode and cathode and with the electrolyzer device. In this work, we have considered all of these parameters altogether to set up a reference PV–EC system for CO2 reduction to hydrocarbons. By using the same original and efficient Cu-based catalysts at both electrodes of the electrolyzer, and by minimizing all possible energy losses associated with the electrolyzer device, we have achieved CO2 reduction to ethylene and ethane with a 21% energy efficiency. Coupled with a state-of-the-art, low-cost perovskite photovoltaic minimodule, this system reaches a 2.3% solar-to-hydrocarbon efficiency, setting a benchmark for an inexpensive all–earth-abundant PV–EC system.ISSN:0027-8424ISSN:1091-649