Chemical hydrogen storage materials – boranes and silanes catalytic solvolysis and dehydrogenation: a mechanistic and regeneration perspective

International audienceHydrogen (H 2 ) has gained a lot of interest as an alternative energy vector, to reduce greenhouse gas emission issues caused by the fossil fuel industry. However, to make hydrogen a real energy carrier in a decarbonated economy, a secure and sustainable supply chain is needed. This approach requires notably safe storage and efficient strategies for recycling of raw materials. We discuss in this survey the state-of-the-art in the field of chemical hydrogen storage (CHS) materials, considering two possible vectors: ammonia borane and hydrosilanes. Regardless of the vector, to achieve real use, it is necessary to understand both the performance of the system and its life cycle, which relates to catalysts structure, and the activation of chemical bonds with efficient and complete catalytic cycles. We give herein an overview of hydrolysis and/or alcoholysis from metals, using coordination complexes, molecular supported catalysts or other materials, including nanocatalysts, with a focus on mechanistic information and understanding. Notably, the studies related to these two vectors can be considered somewhat complementary. Thus, the set of bibliographic report on ammonia borane is very documented in efficient catalytic systems, while its recycling remains at a very early stage. In comparison, hydrosilanes have been much less addressed specifically as a vector for hydrogen, while their reactivity at the molecular scale benefits from a relevant understanding from coordination chemistry studies. In addition, both hydrosilane polymerization and solvolysis reaction enables the release of H 2 , and produces by-products of which added value is already established. This opening the way to economical strategies where recycling can be optional. Nevertheless, the reversibility of hydrosilanes chemistry in H 2 uptake remains attractive and is another option to develop

Rétrospective réflexive sur l’organisation du travail en interdisciplinarité : un projet relatif au nexus moustique-plastique-eau

International audienceOur research project investigates the impact of microplastics on Culex mosquitoes, which are vectors of pathogens. We initially focused on ecology, chemistry, and physics, but then broadened our scope to include the social sciences and humanities. This shift aimed to explore how researchers and stakeholders with various levels of involvement in this project conceived the mosquito-plastic-water nexus. Using semi-structured interviews combined with drawing as a research tool, the study revealed fragmented perspectives of the project, influenced by multiple factors. Some participants felt legitimate only within their specific area of expertise, hesitating to depict aspects beyond their direct involvement. Additionally, limited communication at the project’s outset contributed to a partial view of the latter and a limited understanding of its different parts, steps, and methods. These findings highlight the crucial role of internal communication in fostering a shared understanding among the research team. They also underscore the value of interdisciplinary dialogue, enabling better integration between natural and social sciences to address complex environmental challenges. Finally, they open up the way for interdisciplinary approaches to move towards transdisciplinary approaches.Notre projet de recherche porte sur l’impact des microplastiques sur les moustiques du genre Culex, vecteurs de pathogènes. Nous l’avons d’abord centré sur l’écologie, la chimie et la physique, puis élargi aux sciences humaines et sociales pour mettre en question les représentations que les scientifiques et autres acteurs y étant impliqués avaient du nexus moustique-plastique-eau. Des entretiens semi-directifs, intégrant le dessin comme médium, ont révélé parmi l’équipe des visions fragmentées du projet, influencées notamment par un déficit de communication à son lancement, donnant lieu chez ses membres à un sentiment de légitimité limité à leurs propres domaines d’implication. Cette expérience met ainsi en évidence l’importance d’une communication interne renforcée, tout en ouvrant des réflexions sur l’ouverture des approches interdisciplinaires vers la transdisciplinarité

Smoked fish from Gabon: nutritional benefits vs. contaminant risks

International audienceSmoked fish is the most common form of fish consumption in many African countries. Smoking is likely to cause changes in nutritional value and in the concentration of certain toxic elements. We assessed these changes in the Bonga shad (Ethmalosa fimbriata, Bowdich 1825). Fatty acids (26), vitamin A, trace elements (14) and polycyclic aromatic hydrocarbons (PAHs, 24) were examined in E. fimbriata at different smoking durations (fresh, 24 h, 48 h and 72 h). Composition of smoked fish revealed high inter-individual variability. Smoking did not affect total fatty acid concentrations, but it led to a 4.5-fold decrease in vitamin A and a decrease in the concentrations of Ca, Mg, Mn, Pb and Sr. Meanwhile, it increased the concentrations of PAHs (by a factor of 42), Cd, Mo and Na. Despite these changes, toxic metals (As, Cd and Pb) and PAHs levels remained within safety limits, except for the B(a)P Toxic Equivalent (TEQ) in 72 h-smoked fish. High inter-individual variability in toxic metals, PAHs and nutrients concentrations is suspected to originate from the heterogeneity of the smoking process, and to natural variation in fish. Overall, our results highlight the safety of artisanal smoked fish for human consumption when processed under certain conditions. To further enhance consumer safety, dietary recommendations would advise ensuring fish skin integrity in order to reduce flesh contamination

Positive to negative photoconductance switching in plasmonic gold nanoparticle networks

International audienceThe elaboration of versatile materials in which electrical conduction is tuned by light irradiation is of paramount relevance to such diverse applications as photodetectors, photodiodes, solar cells or light sensors. Although positive photoconductance is increasingly common, systems with negative photoconductance are scarcely reported. In this work, a switching from positive to negative photoconductance is observed upon simple annealing of well-organized networks of gold nanoparticles stabilized by dodecanethiols. The photoconductance properties are investigated experimentally using impedance spectroscopy. The measured Nyquist plots and resonance curves of the impedance are analyzed in terms of equivalent electrical circuits consisting in parallel resistance, capacitance and photoconductance. The positive and negative photo-current conversion efficiencies of the nanoparticles network are estimated k PPC = 389 ± 40 nS.W -1 .cm 2 and k NPC = -241 ± 40 nS.W -1 .cm 2 , respectively. With the aid of density functional theory calculations, the origin of the photoconductance is discussed, at the nanoscale level, in terms of changes of molecular conformation. Such molecular effects assist charge carrier tunneling between first neighbor nanoparticles, and favor the formation of traps introduced by the annealing of the sample. The present work contributes to the understanding of plasmo-electronic properties of hybrid molecule-nanoparticle self-assembled nano-structures.</div

Evaluating Quercus pollen as a valuable archive of past UV-B levels in the Central Mediterranean: Insights from comparative infrared spectroscopy analyses

International audienceThe relative abundance of ultraviolet-absorbing compounds (UACs) in pollen and spore exine increases with prolonged and higher exposure to ultraviolet B (UV-B) radiation. This relationship has been extensively studied via transmission Fourier-transform infrared microspectroscopy (transmission micro-FTIR), primarily in Lycopodium spores and airborne Pinus pollen. However, traditional transmission micro-FTIR methods are prone to infrared light scattering and interference, resulting in spectral deformations and reduced reproducibility. Additionally, bisaccate pollen, like Pinus, can travel long distances and may not accurately reflect local UV-B levels. This study compares transmission and attenuated total reflection (ATR) micro-FTIR methods to assess their reproducibility and investigates Quercus pollen as a potential local UV-B proxy in the Central Mediterranean. Samples containing fresh (in situ), trapped (in mosses), and fossilized (from Holocene sediments) pollen grains were subjected to various chemical treatments, after which the macromolecular composition of single and clustered grains was characterized. Results show that ATR micro-FTIR yields significantly more reproducible data than transmission micro-FTIR, demonstrating the suitability of this method for systematic chemo-palynological studies. Quercus ilex pollen consistently display UAC-related absorption bands across modern and fossil samples, and treatment with hydrochloric acid, hydrofluoric acid, and sodium hydroxide does not significantly alter these signatures. A comparison with fresh and trapped Q. cerris and Q. pubescens pollen further supports these findings. These results suggest that relative UAC concentrations in modern and fossil Quercus exine likely reflect accumulated UV-B dosage, pinpointing Quercus pollen as a valuable local UV-B proxy for reconstructing past UV-B levels in the Central Mediterranea

Un partage d’expérience autour de la pratique de l’interdisciplinarité sur les feux : le projet EcoSoFI (2022-2024)

International audienceLes collaborations inter/transdisciplinaires autour de la compréhension des feux et de leur gestion sont plébiscitées, mais leur mise en œuvre ne va pas pour autant de soi. A partir du partage d’expériences de plusieurs scientifiques et gestionnaires, le présent article restitue la démarche que nous avons adoptée pour comprendre ces difficultés ; et tire quelques constats et propositions. Onconstate notamment la dominance des sciences biophysiques et le poids de la modélisation dans les interfaces entre recherche et gestion. Au sein des SHS, on observe également des partitions entre disciplines et sous-disciplines, ainsi qu’une « interdisciplinarité inachevée » dans l’analyse des changements de régimes de feux. La spécialisation disciplinaire a conduit à une autonomisation du questionnement et des méthodes, qui ne sont plus explicitées ni interrogées au regard des autres approches et du terrain. Nos propositions consistent à remettre en question les catégories implicites concernant les pratiques et les savoirs liés aux feux et à définir des protocoles de recherche permettant des problématisations communes à partir d’études de cas localisées et « concrètes »

Conserving and regenerating the High Atlas cultural landscapes: gendered perspectives from the local Amazigh communities

International audienceLocal communities play a vital role in conserving biocultural diversity; yet their priorities are seldom considered when designing sustainable measures and actions, particularly in remote areas. These processes are frequently developed from urban perspectives, focusing on regional or national scales, and local social dynamics are often overlooked. In this paper, we explore community-based conservation recommendations to develop a strategy for the cultural landscapes of the High Atlas, integrating insights from both local Amazigh voices and academic perspectives. We conducted focus groups with three representative communities in the High Atlas, involving 92 participants. We first documented the environmental changes that both women and men perceived separately. Next, community members provided recommendations for biocultural diversity conservation, which were further discussed among all participants. The participants' perceived changes and the proposed recommendations varied significantly between villages, even over short distances. These variations emerged from each village's primary livelihood and the types of ecosystems on which they depend. Both men and women noted numerous changes in agriculture, pastoralism, and the economy, and suggested actions to address the negative impacts. Women highlighted positive developments in medicinal practices; however, they also pointed out infrastructural deficiencies that hinder human well-being. These discussions served as the grounds for preparing community action plans that guided biocultural conservation action with these populations. Grounding rural development planning, programming, and monitoring in gendered local perceptions and aspirations is crucial for the resilience and adaptation of these landscapes, the people and other non-human living beings inhabiting them

Surface albedo and thermal radiation dynamics under conservation and conventional agriculture in subhumid Zimbabwe

Source Agritrop Cirad (https://agritrop.cirad.fr/614360/) * Autres projets (id;sigle;titre): 101138269;ACCURATE;(EU) Albedo, Conservation agriCUltuRe and climATe bEnefit// FOOD/2021/424–933;RAIZ;(EU) Promoting agroecological intensification for resilience building in Zimbabwe//International audienceWhile conservation agriculture (CA) has been widely evaluated for its biogeochemical effects (e.g soil organic carbon sequestration and greenhouse gas emissions) for climate mitigation, its biogeophysical impacts related to changes in surface albedo remain understudied. This study assessed the biogeophysical effects of CA cropping systems with maize (Zea mays L.) in Zimbabwe. Measurements were conducted continuously over two cropping years at two long-term experiments with contrasting soil characteristics, on an abruptic Lixisol and on a xanthic Ferralsol. The dynamics of surface albedo, longwave radiation, leaf area index, soil moisture and temperature were monitored under three different treatments: conventional tillage (CT, tilled to ~15 cm), no-tillage (NT) and no-tillage with mulch (NTM, 2.5 t DM ha⁻¹). Our results revealed that, on the Ferralsol, NT and NTM significantly (p < 0.05) increased mean annual albedo (0.17) relative to CT (0.16), resulting in a negative instantaneous radiative forcing (iRF) and indicating a net cooling effect. iRF was stronger in 2021/22 (NT: -0.83 ± 0.17 W m-2; NTM: -1.43 ± 0.7 W m-2) than in 2022/23 (NT: -0.43 ± 0.09 W m-2; NTM: -1.03 ± 0.21 W m-2). Conversely, on the Lixisol, while NT increased surface albedo (0.27 vs. CT: 0.24), NTM significantly reduced albedo (0.23), causing positive iRF (warming). iRF was -3.34 ± 0.69 W m-2 and -2.78 ± 0.77 W m-2 for NT in the first and second cropping year, respectively, and increased from 1.14 ± 0.21 W -2 (2021/22) to 2.77 ± 0.41 W m-2 (2022/ 23) under NTM. Overall, our results suggest that the soil background albedo is an important site characteristic that needs to be considered and demonstrates the importance of considering biogeophysical effects when promoting practices of CA for climate change mitigation

Preservation of organic traces of life under Martian conditions: Influence of the nature of the smectite in presence

International audienceClay-rich Martian rocks are considered promising targets in the search for fossilized remains of ancient Martian life. However, the actual influence of the clay mineral compositions in preserving microbial biosignatures remains poorly understood. Here, we explore the biopreservation potential of three pure smectites typically found on Mars and containing Al in their tetrahedral sheets (i.e. a Mg-rich, a Fe-rich and a Al-rich smectite), relying on experiments run using E.&nbsp;coli as a biological analog to simulate hydrothermal alteration scenarios relevant to Mars. The results show that Mg-rich smectites (saponite) are more effective at preserving biomolecules from thermal degradation than Fe-rich and Al-rich smectites (nontronite and beidellite). Plus, in contrast to saponite, neither nontronite nor beidellite appears to significantly trap (and thus preserve) organic compounds within their interlayer spaces. Overall, the present study highlights that both the chemistry and the abundance of organic material in ancient Martian clay-rich rocks will depend on the compositional nature of smectites initially present

Dyadic Ru-based nanomaterials for visible light-driven photocatalytic hydrogen evolution

International audienceVisible light-driven water splitting is an appealing strategy to store renewable energy in the chemical bonds of molecular hydrogen. In this regard, the development of photocatalytic architectures where charge transfer and recombination can be controlled represents a key challenge. The surface functionalization of Ru/RuO 2 nanoparticles (NPs) with the [Ru(2,2′-bpy) 2 (qpy)](PF 6 ) 2 photosensitizer (PS), yielding PS-NPs "dyadic" hybrid nanomaterials, represents a promising strategy. Four HER photocatalysts with different PS:NPs ratios are synthesized and thoroughly characterized by analytical and spectroscopic techniques. X-ray photoelectron spectroscopy (XPS) reveals the covalent binding of the PS to the NPs surface. Analysis of the photocatalytic performance in aqueous triethanolamine (TEOA) shows that the activation of the nanocatalyst (RuO 2 reduction) and the hydrogen evolution rate improves when the PS loading increases. Under visible-light irradiation, the nanomaterials with higher PS loading show sustained production of hydrogen for at least 80 h. The morphological and compositional evolution of the hybrid nanomaterials under photocatalytic conditions is studied and correlated with hydrogen production rates over time, pointing to a sequential leaching of PS from the nanomaterials surface. Additionally, photophysical experiments allow attaining an insight into the photochemical mechanism, which involves oxidative quenching with a fast electron injection, but also fast back electron transfer.</div