Photocatalytic activity of a new composite material of Fe (III) oxide nanoparticles wrapped by a matrix of polymeric carbon nitride and amorphous carbon

Polymeric carbon nitride was synthesized from urea and doped with Cu and Fe to act as co-catalysts. The material doped with Fe was a new composite material composed of Fe(III) oxides (acting as a co-catalyst) wrapped by the polymer layers and amorphous carbon. Furthermore, the copper doped material was described in a previous report. The photocatalytic degradation of the azo dye direct blue 1 (DB) was studied using as photocatalysts: pure carbon nitride (CN), carbon nitride doped with Cu (CN-Cu) and carbon nitride doped with Fe (CN-Fe). The catalysts were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), by X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller method (BET), etc. The adsorption phenomenon was studied using the Langmuir and Freundlich models. For the kinetic study, a solution of 500 mg L-1 of DB1 was treated with each catalyst, visible light and H2O2. The dye concentration was measured by spectrophotometry at the wavelength of 565 nm, and the removal of the total organic content (TOC) was quantified. BET analysis yielded surface areas of 60.029, 20.116 and 70.662 m2g-1 for CN, CN-Cu and CN-Fe, respectively. The kinetics of degradation were pseudo-first order, whose constants were 0.093, 0.039 and 0.110 min-1 for CN, CN-Cu and CN-Fe, respectively. The total organic carbon (TOC) removal reached the highest value of 14.46% with CN-Fe

Composición química y caracterización calorimétrica de híbridos y variedades de maíz cultivadas en México

Se estudió la composición química y comportamiento térmico de veinte híbridos y variedades de maíz, del programa de cruzamiento del INIFAP-Iguala, México. Los granos de maíz semicristalinos y cristalinos tuvieron menor contenido de humedad que aquellos del tipo semidentado y dentado los cuales, a su vez, tuvieron los valores más altos de proteína. Las variedades de maíz de calidad proteínica (QPM) no tuvieron el mayor contenido de proteína. La temperatura de gelatinización (determinada por calorimetría diferencial de barrido) estuvo entre 73.4-77.1 °C y la entalpía entre 1.9-4.7 J g-1. Este resultado es importante para el diseño de equipos de cocimiento o tratamientos térmicos del grano de maíz, como en la producción de tortillas

Tuning the oxygen reduction activity and stability of Ni(OH)2@Pt/C catalysts through controlling Pt surface composition, strain, and electronic structure.

Nanoparticles of Ni(OH)2 surrounded with ultra-low Pt content and supported on functionalized carbon were prepared by a scalable synthesis method and investigated as electrocatalysts for the oxygen reduction reaction (ORR) in acidic media. The effect of altering the Pt surface composition on the Ni(OH)2 nanoparticle core was investigated as a route to simultaneously increase the ORR activity and stability. Modifying the Pt surface composition resulted in both structural and electronic changes. Decreasing the Pt surface composition resulted in stronger Pt-Pt compressive strain and decrease in the occupancy of d-band vacancies per atom. The correlation of strain and d-vacancies with ORR activity and stability showed a Volcano-type tendency, with the 6 wt. % Pt sample showing the highest activity and stability. The electrochemical results obtained using rotating disk electrode (RDE) tests showed an enhancement of about six times higher surface and mass-normalized activity as well as improved durability compared to commercial Pt/C. These improvements were further corroborated by single cell membrane electrode assembly (MEA) tests where similar trends were observed, showing higher power densities with lower Pt loadings, in comparison with commercial Pt/C. These results show that new electrocatalysts with higher activity and stability can be obtained through precise control of the atomic-level catalyst structure

SEM and XAS characterization at beginning of life of Pd-based cathode electrocatalysts in PEM fuel cells

The fuel cell performance of membrane electrode assemblies with a Pt anode and Pd, PdCu or Pd5Cu4Pt cathodes has been tested during 116 h (beginning of life). The incorporation of Cu to Pd increases the fuel cell performance. Incorporation of Pt leads to further improvement. SEM micrographs of the as-prepared and the fuel cell-tested assemblies show the effects of the 116 h of continuous operation. Nafion membranes were characterized by small angle X-ray scattering. The results show a reduction of the size of the lamellar domains in the perfluorinated matrix after fuel cell testing, but no correlation with the cathode electrocatalyst material. The cathode electrocatalysts were characterized by ex-situ synchrotron radiation X-ray diffraction and X-ray absorption spectroscopy at the Pd L-3, Cu K and Pt L-3 edges. Re-organization of Pd5Cu4Pt electrocatalyst after fuel cell testing was observed. The Cu in the electrocatalyst can be described as a nano-mixture of metallic Cu, alloyed Cu and CuO. The CuO acts as a promoter of the ORR. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved