Tailoring the porosity of chemically activated hydrothermal carbons: Influence of the precursor and hydrothermal carbonization temperature

Advanced porous materials with tailored porosity (extremely high development of microporosity together with a narrow micropore size distribution (MPSD)) are required in energy and environmental related applications. Lignocellulosic biomass derived HTC carbons are good precursors for the synthesis of activated carbons (ACs) via KOH chemical activation. However, more research is needed in order to tailor the microporosity for those specific applications. In the present work, the influence of the precursor and HTC temperature on the porous properties of the resulting ACs is analyzed, remarking that, regardless of the precursor, highly microporous ACs could be generated. The HTC temperature was found to be an extremely influential parameter affecting the porosity development and the MPSD of the ACs. Tuning of the MPSD of the ACs was achieved by modification of the HTC temperature. Promising preliminary results in gas storage (i.e. CO2 capture and high pressure CH4 storage) were obtained with these materials, showing the effectiveness of this synthesis strategy in converting a low value lignocellulosic biomass into a functional carbon material with high performance in gas storage applications.

Prácticas de autocuidado sexual y reproductivo en mujeres “parejas de” migrantes internacionales de San Luis Potosí, México

Los migrantes y sus parejas han sido incorporados en los discursos institucionales de salud como “sujetos en riesgo” frente a las Infecciones de Trasmisión Sexual (ITS), sin embargo la incorporación de esta población específica en la comunicación y gestión del riesgo de ITS ha sido ambigua en el contexto mexicano. El objetivo del presente acercamiento fue conocer las prácticas de autocuidado sexual y reproductivo que adoptan en su cotidianeidad mujeres parejas de migrantes y la relación de dichas medidas con la comunicación y gestión del riesgo que los Servicios de Salud realizan. Se trató de una aproximación de tipo cualitativo con 20 mujeres “de migrantes” localizadas mediante los servicios de salud, la información se recabó a través de entrevistas a profundidad que focalizaron en las esferas de “percepción del riesgo” y “Autocuidado sexual y reproductivo”. Se encontró que la mayoría de las mujeres no se reconoce vulnerable frente a las ITS y que la percepción del riesgo no es determinante en la confrontación que respecto a la amenaza puedan desarrollar, dado que los imaginarios patriarcales que prevalecen en ellas, sus parejas y el personal de salud desestiman la utilización de medidas de prevención y detección oportuna.

Sonochemical synthesis of graphene oxide supported Pt–Pd alloy nanocrystals as efficient electrocatalysts for methanol oxidation

Pt–Pd bimetallic nanoparticles supported on graphene oxide (GO) nanosheets were prepared by a sonochemical reduction method in the presence of polyethylene glycol as a stabilizing agent. The synthetic method allowed for a fine tuning of the particle composition without significant changes in their size and degree of aggregation. Detailed characterization of GO-supported Pt–Pd catalysts was carried out by transmission electron microscopy (TEM), AFM, XPS, and electrochemical techniques. Uniform deposition of Pt–Pd nanoparticles with an average diameter of 3 nm was achieved on graphene nanosheets using a novel dual-frequency sonication approach. GO-supported bimetallic catalyst showed significant electrocatalytic activity for methanol oxidation. The influence of different molar compositions of Pt and Pd (1:1, 2:1, and 3:1) on the methanol oxidation efficiency was also evaluated. Among the different Pt/Pd ratios, the 1:1 ratio material showed the lowest onset potential and generated the highest peak current density. The effect of catalyst loading on carbon paper (working electrode) was also studied. Increasing the catalyst loading beyond a certain amount lowered the catalytic activity due to the aggregation of metal particle-loaded GO nanosheets.