CO2 methanation catalyzed by oriented MoS2 nanoplatelets supported on few layers graphene

[EN] Powders of molybdenum disulfide platelets strongly grafted on graphene have been prepared by pyrolysis of ammonium alginate containing adsorbed various proportions of (NH4)(2)MoS4. After pyrolysis, formation of MoS2 supported on graphene was determined by XRD and electron microscopy and spectroscopic techniques. MoS2/G exhibits catalytic activity for the methanation of CO2, the performance being optimal at intermediate loadings. The catalytic activity of sharply contrasts with that of bulk MoS2 that promotes the reverse water gas shift, affording CO as the main product. Characterization of the spent MoS2/G catalyst shows the partial conversion of external MoS2 into MoO3. Comparison of the catalytic activity of MoS2/G with that of MoO3/G shows that the latter is less efficient, but more selective for CO2 methanation.Vasile I. Parvulescu kindly acknowledges UEFISCDI for financial support (project PN-III-P4-ID-PCE-2016-0146, Nr. 121/2017 and project PN-III-P1-1.2-PCCDI-2017-0541). Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa and CTQ2015-69653-CO2-R1) and Generalitat Valencia (Prometeo 2017-083) is gratefully acknowledged. A.P. also thanks the Spanish Ministry for a Ramon y Cajal research associate contract.Primo Arnau, AM.; He, J.; Jurca, B.; Cojocaru, B.; Bucur, C.; Parvulescu, VI.; García Gómez, H. (2019). CO2 methanation catalyzed by oriented MoS2 nanoplatelets supported on few layers graphene. Applied Catalysis B Environmental. 245:351-359. https://doi.org/10.1016/j.apcatb.2018.12.034S35135924

Co-Fe Clusters Supported on N-Doped Graphitic Carbon as Highly Selective Catalysts for Reverse Water Gas Shift Reaction

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Sustainable Chemistry & Engineering, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acssuschemeng.1c01401[EN] Graphitic carbons are suitable supports of metal nanoparticles with catalytic activity. In the present study, the preparation of N-doped graphitic carbon supporting clusters of Fe-Co alloys starting from biomass waste is reported. These sub-nanometric Co-Fe clusters supported on N-doped graphitic carbon at a metal loading below 0.2 wt % exhibit high activity for the selective hydrogenation of CO2 to CO. Operating at 500 degrees C and 10 bar with an H-2/CO2 molar ratio of 7 and a space velocity of 600 h(-1), a conversion of 56% with a selectivity of over 98% to CO, and remarkable stability over 30 h operation was obtained. Interestingly, analogous catalysts based on N-doped graphitic carbon with much higher Co-Fe loadings and an average particle size range of 1-5 nm exhibit only half of this activity, with similar CO selectivity. This contrasting behavior reveals the dramatic effect of the particle size on the catalytic activity. In comparison, SiO2 as support under similar conditions affords CH4 as the main product.Financial support by the Spanish Ministry of Science, Innovation, and University (Severo Ochoa and RTI2018.98237-B-CO1) and Generalitat Valenciana (Prometeo 2017/083) is gratefully acknowledged. L.P. thanks the Generalitat Valenciana for a Santiago Grisolia scholarship. BASF is thanked for financial support.Peng, L.; Jurca, B.; Primo Arnau, AM.; Gordillo, A.; Parvulescu, VI.; García Gómez, H. (2021). Co-Fe Clusters Supported on N-Doped Graphitic Carbon as Highly Selective Catalysts for Reverse Water Gas Shift Reaction. ACS Sustainable Chemistry & Engineering. 9(28):9264-9272. https://doi.org/10.1021/acssuschemeng.1c014019264927292

N-Doped Defective Graphene from Biomass as Catalyst for CO2 Hydrogenation to Methane

This is the peer reviewed version of the following article: B. Jurca, C. Bucur, A. Primo, P. Concepción, V. I. Parvulescu, H. García, ChemCatChem 2019, 11, 985, which has been published in final form at https://doi.org/10.1002/cctc.201801984. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.[EN] N-doped, defective graphene obtained by pyrolysis of chitosan at 900 degrees C under Ar exhibits catalytic activity for the Sabatier hydrogenation of CO2 to CH4 at temperatures about 500 degrees C with estimated turnover frequencies and activation energy values of 73.17s(-1) and 24.3 kcal x mol(-1), respectively. It has been found that this enhanced catalytic activity compared to other related doped defective graphenes derives from the presence of pyridinic N atoms that adsorbs CO2 forming carbamate-type adsorbates.Financial support by the Spanish Ministry of Economy and Competitiveness (Severo Ochoa, Grapas and CTQ2015-69153-CO2-R1) and Generalitat Valenciana (Prometeo 2017-083) is gratefully acknowledged. A.P. thanks the Spanish Ministry for a Ramon y Cajal research associate contract. V.I.P. kindly acknowledges UEFISCDI for financial support (projects PN-III-P4-ID-PCE-2016-0146, Nr. 121/2017, PN-III-P4-ID-PCCF-2016-0088 and PN-III-P1-1.2-PCCDI-2017-0541). Cristina Bucur thanks IFTM for the financial support.Jurca, B.; Bucur, C.; Primo Arnau, AM.; Concepción Heydorn, P.; Parvulescu, VI.; García Gómez, H. (2019). N-Doped Defective Graphene from Biomass as Catalyst for CO2 Hydrogenation to Methane. ChemCatChem. 11(3):985-990. https://doi.org/10.1002/cctc.201801984S98599011

Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO2 Hydrogenation

[EN] Starting from the reported activity of Co-Fe nanoparticles wrapped onto graphitic carbon (Co-Fe@C) as CO2 hydrogenation catalysts, the present article studies the influence of a series of metallic (Pd, Ce, Ca, Ca, and Ce) and non-metallic (S in various percentages and S and alkali metals) elements as Co-Fe@C promoters. Pd at 0.5 wt % somewhat enhances CO2 conversion and CH4 selectivity, probably due to H-2 activation and spillover on Co-Fe. At similar concentrations, Ce does not influence CO2 conversion but does diminish CO selectivity. A 25 wt % Fe excess increases the Fe-Co particle size and has a detrimental effect due to this large particle size. The presence of 25 wt % of Ca increases the CO2 conversion and CH4 selectivity remarkably, the effect being attributable to the CO2 adsorption capacity and basicity of Ca. Sulfur at a concentration of 2.1% or higher acts as a strong poison, decreasing CO2 conversion and shifting selectivity to CO. The combination of S and alkali metals as promoters maintain the CO selectivity of S but notably increase the CO2 conversion. Overall, this study shows how promoters and poisons can alter the catalytic activity of Co/Fe@C catalysts, changing from CH4 to CO. It is expected that further modulation of the activity of Co/Fe@C catalysts can serve to drive the activity and selectivity of these materials to any CO2 hydrogenation products that are wanted.This research was funded by the Spanish Ministry of Science and Innovation and the University (Severo Ochoa SEV2021 and RTI2018.98237-B-CO1) and Generalitat Valenciana (Prometeo 2017/083). A.P. is the recipient of a Ramon y Cajal research associate contract awarded by the Spanish Ministry of Science and Innovation. L.P. thanks the Generalitat Valenciana for a Santiago Grisolia scholarship. BASF is thanked for financial support.Jurca, B.; Peng, L.; Primo Arnau, AM.; Gordillo, A.; Dhakshinamoorthy, A.; Parvulescu, VI.; García Gómez, H. (2022). Promotional Effects on the Catalytic Activity of Co-Fe Alloy Supported on Graphitic Carbon for CO2 Hydrogenation. Nanomaterials. 12(18):1-13. https://doi.org/10.3390/nano12183220113121

Salvia officinalis L. extract increase the antitumor effect of Doxorubicin on Ehrlich carcinoma tumor cells

The current study demonstrated the superior in vivo antitumor activity of the association between Salvia officinalis L. and Doxorubicin as compared with Doxorubicin alone and its lack of toxicity. The study was carried out on 32 Mus musculus female mice, for 14 days long. The tumor model was Ehrlich Ascites Carcinoma (EAC). Animals were divided in four equal groups of 8 mice: normal control, tumor control, EAC + doxorubicin and EAC + doxorubicin + Salvia officimalis L. All the values that reflect the tumor development (difference in body weight, EAC volume and cellular concentration) were improved in significant manner. Hematological and biochemistry parameters determination were performed for all four groups of mice and no cytotoxicity was found. The efficacy of Salvia officinalis L. as an adjuvant therapy in cancer has been demonstrated

Heterogeneous contributions of change in population distribution of body mass index to change in obesity and underweight NCD Risk Factor Collaboration (NCD-RisC)

From 1985 to 2016, the prevalence of underweight decreased, and that of obesity and severe obesity increased, in most regions, with significant variation in the magnitude of these changes across regions. We investigated how much change in mean body mass index (BMI) explains changes in the prevalence of underweight, obesity, and severe obesity in different regions using data from 2896 population-based studies with 187 million participants. Changes in the prevalence of underweight and total obesity, and to a lesser extent severe obesity, are largely driven by shifts in the distribution of BMI, with smaller contributions from changes in the shape of the distribution. In East and Southeast Asia and sub-Saharan Africa, the underweight tail of the BMI distribution was left behind as the distribution shifted. There is a need for policies that address all forms of malnutrition by making healthy foods accessible and affordable, while restricting unhealthy foods through fiscal and regulatory restrictions

Synthèse et caractérisation de pérovskites doubles magnétorésistives dérivées de Sr2FeMoO6

Thèse en cotutelle préparée au Laboratoire de Physico-Chimie de l'État Solide, Université Paris XI, Orsay, France et au Département de Chimie Physique, Université de Bucarest, Roumanie Soutenue à Orsay, le 20 décembre 2004, devant le jury composé de : Mme Agnès Barthélémy, Professeur, Université Paris XI, Président ; M. Marius Andruh, Professeur, Université de Bucarest, Rapporteur ; Mme Christine Martin, Directrice de Recherche, CRISMAT Caen, Rapporteur ; M. Patrick Berthet, Professeur, Université Paris XI, Examinateur ; M. Eugen Segal, Professeur, Université de Bucarest, ExaminateurThis work is devoted to the synthesis and physico-chemical characterization of Sr2FeMoO6, Sr2FexMo2-xO6 (x = 0.9-1.33) and Sr2FeCrxMo1-xO6 (x = 0.1-0.25) double perovskites. For Sr2FeMoO6 the solid state synthesis conditions influence the microstructure of the samples and the Fe/Mo order. Successive sintering treatments with intermediate grindings improve the saturation magnetization (3.8 µB) which became close to the ideal value (4 µB) and the low field magnetoresistance (LFMR) from 1.58 ± 0.14 % to 2.74 ± 0.01 % (T = 300 K, H = 1 kOe) as a consequence of microstructural changes. The effective magnetic moment values depict the presence of mixed valency states: FeII/MoVI and FeIII/MoV. The Sr2FexMo2-xO6 solid solutions (tetragonal symmetry or cubic for x > 1.2) are stable for a larger excess of iron than of molybdenum. The Fe/Mo order diminishes when the difference between x and 1 becomes larger and is stabilizing to an equilibrium value after a high number of sintering treatments for a given x. The Tc arises with x (Fe-Fe couplings stronger than Fe-Mo), but the saturation magnetization is maximum for x = 1. The resistivity enhances with x (delocalized electrons come from molybdenum) presenting thus a stronger dependence of the chemical composition than the microstructure. The magnetoresistance is maximum for x = 1 ; for x = 1.33 the composition ceases to be a half-metal. For Sr2FeCrxMo1-xO6 solid solutions, the increase of chromium content determines the diminution of octahedral sites cationic order and thus a decrease of Tc, magnetization and magnetoresistance.Cette thèse concerne la synthèse et l'étude des propriétés physico-chimiques des pérovskites doubles Sr2FeMoO6, Sr2FexMo2-xO6 (x = 0,9-1,33) et Sr2FeCrxMo1-xO6 (x = 0,1-0,25). Pour Sr2FeMoO6 les conditions de synthèse à l'état solide influencent la microstructure des échantillons et l'ordre Fe/Mo. Des frittages successifs avec des broyages intermédiaires entraînent ainsi une augmentation de l'aimantation à saturation (3,8 µB) qui s'approche de la valeur idéale (4 µB) et améliorent la magnétorésistance en champ faible (LFMR) de 1,58 ± 0,14 % à 2,74 ± 0,01 % (T = 300 K, H = 1 kOe) en raison des modifications microstructurales. Les valeurs des moments magnétiques effectifs montrent la présence de valences mixtes: FeII/MoVI et FeIII/MoV. Les compositions Sr2FexMo2-xO6 (quadratiques ou cubiques pour x > 1,2) acceptent un plus grand excès de fer que de molybdène. L'ordre Fe/Mo diminue quand x s'écarte de 1 et tend vers une valeur d'équilibre après un grand nombre de traitements de frittage pour un x donné. La Tc augmente avec x (couplages Fe-Fe plus forts que les couplages Fe-Mo), tandis que l'aimantation à saturation est maximum pour x = 1. La résistivité augmente avec x (les électrons délocalisés proviennent du molybdène), elle dépend davantage de la composition chimique que de la microstructure. La magnétorésistance est maximum pour x = 1; pour x = 1,33 le matériau cesse d'être un demi-métal. Pour la série Sr2FeCrxMo1-xO6 l'augmentation du contenu en chrome détermine la diminution de l'ordre des cations sur les sites octaédriques et par conséquent une baisse de Tc, d'aimantation et de magnétorésistance

Synthèse et caractérisation de pérovskites doubles magnétorésistives dérivées de Sr2FeMoO6

Cette thèse concerne la synthèse et l'étude des propriétés physico-chimiques des pérovskites doubles Sr2FeMoO6, Sr2FexMo2-xO6 (x = 0,9-1,33) et Sr2FeCrxMo1-xO6 (x = 0,1-0,25). Pour Sr2FeMoO6 les conditions de synthèse à l'état solide influencent la microstructure des échantillons et l'ordre Fe/Mo. Des frittages successifs avec des broyages intermédiaires entraînent ainsi une augmentation de l'aimantation à saturation (3,8 B) qui s'approche de la valeur idéale (4 B) et améliorent la magnétorésistance en champ faible (LFMR) de 1,58+-0,14 % à 2,74+-0,01 % (T = 300 K, H = 1 kOe) en raison des modifications microstructurales. Les valeurs des moments magnétiques effectifs montrent la présence de valences mixtes: FeII/MoVI et FeIII/MoV. Les compositions Sr2FexMo2-xO6 (quadratiques ou cubiques pour x > 1,2) acceptent un plus grand excès de fer que de molybdène. L'ordre Fe/Mo diminue quand x s'écarte de 1 et tend vers une valeur d'équilibre après un grand nombre de traitements de frittage pour un x donné. La Tc augmente avec x (couplages Fe-Fe plus forts que les couplages Fe-Mo), tandis que l'aimantation à saturation est maximum pour x = 1. La résistivité augmente avec x (les électrons délocalisés proviennent du molybdène), elle dépend davantage de la composition chimique que de la microstructure. La magnétorésistance est maximum pour x = 1; pour x = 1,33 le matériau cesse d'être un demi-métal. Pour la série Sr2FeCrxMo1-xO6 l'augmentation du contenu en chrome détermine la diminution de l'ordre des cations sur les sites octaédriques et par conséquent une baisse de Tc, d'aimantation et de magnétorésistance.This work is devoted to the synthesis and physico-chemical characterization of Sr2FeMoO6, Sr2FexM02-xO6 (x = 0.9-1.33) and Sr2FeCrxMo1-xO6 (x = 0.1-0.25) double perovskites. For Sr2FeMoO6 the solid state synthesis conditions influence the microstructure of the samples and the Fe/Mo order. Successive sintering treatments with intermediate grindings improve the saturation magnetization (3.8 B) which became close to the ideal value (4 B) and the low field magnetoresistance (LFMR) from 1.58+-0.14 % to 2.74+-0.01 % (T = 300 K, H = 1 kOe) as a consequence of microstructural changes. The effective magnetic moment values depict the presence of mixed valency states: FeII/MoVI and FeIII/MoV. The Sr2FexMO2-xO6 solid solutions (tetragonal symmetry or cubic for x > 1.2) are stable for a larger excess of iron than of molybdenum. The Fe/Mo order diminishes when the difference between x and 1 becomes larger and is stabilizing to an equilibrium value alter a high number of sintering treatments for a given x. The Tc arises with x (Fe-Fe couplings stronger than Fe-Mo), but the saturation magnetization is maximum for x = 1. The resistivity enhances with x (delocalized electrons come from molybdenum) presenting thus a stronger dependence of the chemical composition than the microstructure. The magnetoresistance is maximum for x = 1 ; for x = 1.33 the composition ceases to be a half-metal. For Sr2FeCrxM01-xO6 solid solutions, the increase of chromium content determines the diminution of octahedral sites cationic order and thus a decrease of Tc, magnetization and magnetoresistance.ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF