Ali M. Huerta-Flores

Fabrication and characterization of a nanostructured TiO2/In2S3-Sb2S3/CuSCN extremely thin absorber (eta) solar cell

In this work we report the successful assembly and characterization of a TiO2/In2S3-Sb2S3/CuSCN extremely thin absorber solar cell. Nanostructured TiO2 deposited by screen printing on an ITO substrate was used as an n-type electrode. An ~80 nm extremely thin layer of the system In2S3-Sb2S3 deposited by successive ionic layer adsorption and a reaction (silar) method was used as an absorber. The voids were filled with p-type CuSCN and the entire assembly was completed with a gold contact. The solar cell fabricated with this heterostructure showed an energy conversion efficiency of 4.9%, which is a promising result in the development of low cost and simple fabrication of solar cells.

Hybrid SrZrO 3 -MOF heterostructure: surface assembly and photocatalytic performance for hydrogen evolution and degradation of indigo carmine dye

In this work, we developed a novel heterostructure based on the coupling of a metal organic framework (MOF LEEL-037) with an inorganic semiconductor (SrZrO3) for two photocatalytic applications: hydrogen evolution from water splitting and the degradation of indigo carmine dye. A complete study of the structural, morphological, textural, optical, electronic, and electrochemical properties of MOF, SrZrO3 and the heterostructure is presented through X-ray diffraction, scanning electron microscopy, UV–Vis diffuse reflectance spectroscopy (UV–Vis), photoluminescence spectroscopy and electrochemical impedance spectroscopy, evaluating the effect of these parameters on the catalytic performance of the materials. The heterostructure formation was studied by transmission electron microscopy, varying the loading of LEEL-037 from 0.5 to 5%. Microscope images corroborate the effective dispersion of LEEL-037 and the appropriate contact between the metal organic framework and SrZrO3 particles. It was found that the photocatalytic activity of SrZrO3 under UV light was significantly enhanced with the incorporation of MOF LEEL-037, which enhances the charge separation and transport, leading to an improved photocatalytic performance. After 1xa0h of reaction, the heterostructure with the optimal amount of LEEL-037 (5%) exhibited a hydrogen evolution of 66.9xa0µmol, corresponding to 6 times the activity of pure SrZrO3 (11.2xa0µmol). LEEL-037 exhibited an activity of 34.1xa0µmol, but the rate of hydrogen production was not constant. The stability and efficiency of the charge transference in the bare semiconductors and the heterostructure were studied through photoluminescence and electrochemical analysis, which demonstrated the suitable band coupling between SrZrO3 with MOF LEEL-037, the enhanced charge separation and injection from one semiconductor to another, and the reduction in the recombination of the electron–hole pairs. These studies and the integral correlation of the properties of the materials allowed to establish the path of the photogenerated charges and to propose the photocatalytic mechanisms involved in the reactions. The photocatalysts were also evaluated for the degradation of indigo carmine, where the highest dye degradation (69%) was exhibited by the heterostructure. Based on our results, we propose the use of the heterostructure SrZrO3-5% MOF LEEL-037, obtained by an easy and low cost method, as a suitable new photocatalytic material for environmental and energy applications, highlighting at the same time the promising properties of metal–organic frameworks for their coupling with a variety of inorganic semiconductors.

Green synthesis of earth-abundant metal sulfides (FeS2, CuS, and NiS2) and their use as visible-light active photocatalysts for H2 generation and dye removal

Earth-abundant metal sulfides (for example, FeS2, CuS, and NiS2) are promising materials to be used as photocatalysts due to their suitable electronic and optical properties. In this work, we present a fast and low-cost hydrothermal method to synthesize these materials. They are integrally characterized and evaluated as photocatalysts for the H2 evolution reaction and the degradation of indigo carmine (IC). FeS2 exhibits the highest photocatalytic efficiency (32xa0µmolxa0g−1xa0h−1 of H2 evolution and 88% of indigo carmine degradation) under visible light, and this activity is attributed to a larger crystallite size, smaller particle size, and lower recombination, compared to CuS and NiS2. Moreover, three different sacrificial reagents are studied for the H2 evolution reaction, including Na2S/Na2SO3, EDTA, and ethanol. Na2S/Na2SO3 shows the highest enhancement in the activity, increasing the rate of H2 production more than 15 times. This behavior is related to the lower oxidation potential of Na2S/Na2SO3. Moreover, we evaluate the activity of the materials for the electrochemical hydrogen evolution reaction (HER). In summary, this work provides valuable information for effective applications of these earth-abundant metal sulfides for energy and environmental photocatalytic processes.

Extended visible light harvesting and boosted charge carrier dynamics in heterostructured zirconate–FeS2 photocatalysts for efficient solar water splitting

Limited visible light absorption, slow charge transference, and high recombination are some of the main problems associated with low efficiency in photocatalytic processes. For these reasons, in the present work, we develope novel zirconate–FeS2 heterostructured photocatalysts with improved visible light harvesting, effective charge separation and high photocatalytic water splitting performance. Herein, alkali and alkaline earth metal zirconates are prepared by a solid state reaction and coupled to FeS2 through a simple wet impregnation method. The incorporation of FeS2 particles induces visible light absorption and electron injection in zirconates, while the appropriate coupling of the semiconductors in the heterostructure allows an enhanced charge separation and suppression of the recombination. The obtained heterostructures exhibit high and stable photocatalytic activity for water splitting under visible light, showing competitive efficiencies among other reported materials. The highest hydrogen evolution rate (4490xa0µmolxa0g−1xa0h−1) is shown for BaZrO3–FeS2 and corresponds to more than 20 times the activity of the bare BaZrO3. In summary, this work proposes novel visible light active heterostructures for efficient visible light photocatalytic water splitting.