Juan Matos

This work reports, for the first time, the use of agave bagasse from “Tequila Weber Var” as an efficient and eco-friendly template for the microwave-assisted solvothermal synthesis of C@TiO₂ photoelectrodes. The characterization of the C@TiO₂ materials was performed using composition and elemental analysis, diffuse reflectance/UV-visible spectroscopy, N₂ adsorption/desorption isotherms, scanning and transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction patterns, cyclic voltammetry, impedance spectroscopy, and variations of the open-circuit potential in a conventional electrochemical cell. Three 1:1, 4:1, and 8:1 agave:Ti volume ratios were used to explore the influence of carbon content upon the optical and photoelectric properties of TiO₂. The composite with a 1:1 ratio showed a charge transfer kinetic capacity of 0.86 C·cm⁻²·s⁻¹ with the highest current density flow of 2.2 mA·cm⁻², and the lowest optical band gap (E_bg) value of 2.92 eV, boosting the optoelectronic behavior of TiO₂. The photoanode composed of FTO/C@TiO₂ with the hybrid material with a 1:1 ratio was preliminarily evaluated in a photovoltaic solar cell, showing a light-to-electricity conversion efficiency higher than the other two composites and up to 12.5 times higher than the photoanode only composed of neat TiO₂. The present results contribute to the state-of-the-art of eco-friendly organic–inorganic thin film photoelectrodes for the sustainable synthesis of third-generation solar cells using bagasse-derived waste as an efficient carbon source for the synthesis of hybrid photoactive semiconductors.

Bismuth oxyiodide (BiOI) microspheres were synthesized by a microwave-assisted solvothermal method at 126 °C in only 4 min, a significantly shorter reaction time than in previously reported works. The structural, surface, morphological, and optical properties of BiOI were analyzed and correlated with the photocatalytic activity during the degradation of gallic acid (GA) and the photo-oxidation of nitric oxide (NO) in the aqueous and gas phases, respectively. The BiOI microspheres exhibited higher first-order apparent rate constants for GA and NO (0.188 min⁻¹ and 0.230 min⁻¹) than the benchmark TiO₂ P25 (0.101 min⁻¹ and 0.066 min⁻¹). In addition, in steady-state reaction conditions (after 10 min), BiOI achieved 86% degradation of GA instead of the 63% degradation observed with TiO₂ P25. Furthermore, at the same point in the reaction, the BiOI microspheres showed up to 65% NO conversion, while TiO₂ P25 only achieved 15%. Accordingly, the results suggest that the microwave-assisted solvothermal method provides significant advantages for rapid, low-cost, and eco-friendly synthesis of BiOI microspheres for photocatalytic remediation of polluted water and air.

The influence of texture and surface chemistry of porous carbons on the activity, selectivity, and stability of Ni, Mo, and NiMo‐based catalysts was verified in the hydrogenation of ethylene. A homemade nanoporous carbon was prepared from pine bark and compared against two commercial activated carbon‐supported NiMo catalysts. The temperature and type of reducing pretreatments were studied, and results showed that nanoporous carbon‐supported NiMo catalysts are less prone to deactivate than catalysts supported on commercial micro‐ or mesoporous activated carbons. The careful characterization of catalysts performed before and after reaction suggests that the selectivity of gaseous products can be related to a confining effect of ethylene within the nanopores of the carbon support. Nanoporous carbon‐supported Ni and NiMo catalysts did not deactivate due to the formation of carbon nanotubes, permitting the diffusion of active Ni nanoparticles from the pore framework to the surface of the catalysts, inducing changes in the selectivity of gaseous products along the reaction. A schematic mechanism of reaction explaining the hydrogenolysis/hydrogenation selectivity is proposed based on the changes in selectivity of gaseous products and the postmortem characterization of catalysts, referring to the surface chemistry, formation of carbon nanotubes, diffusion of metallic species, and changes in the porosimetry of catalysts.

This work shows a sustainable methodology for the synthesis of biogenic materials designed for the removal and photodegradation of rhodamine B (RhB), a highly dangerous environmental pollutant that induces reproductive toxicity. The classical synthesis of MCM-41-ordered mesoporous materials was modified using biocompatible rice husk as the silica template. Iron was incorporated and the so-prepared biogenic photocatalysts were characterized by X-ray diffraction, N₂ adsorption–desorption isotherms, transmission electron microscopy, diffuse reflectance UV-Vis, surface pH, cyclic voltammetry, and Fourier transform infrared spectral analysis of pyridine adsorption. The photocatalytic performance of the materials was evaluated following the removal by adsorption and the photon-driven degradation of RhB. The adsorption capacity and photocatalytic activity of the biogenic materials were correlated with their properties, including iron content, texture, surface content, and electrochemical properties. The best biogenic material boosted the degradation rates of RhB under UV irradiation up to 4.7 and 2.2 times greater than the direct photolysis and the benchmark semiconductor TiO₂-P25. It can be concluded that the use of rice husks for the synthesis of biogenic Fe-modified mesoporous materials is a promising strategy for wastewater treatment applications, particularly in the removal of highly toxic organic dyes.

Nickel-decorated carbocatalysts were synthesized by the evaporation-induced self-assembly (EISA) method. The influence of the metal content and pyrolysis temperature upon the photoactivity was assessed through rhodamine B degradation under UV irradiation. The characterization revealed a mesoporous framework with a granular morphology composed of amorphous carbon, where the pyrolysis temperature influenced the metal dispersion on the carbon surface. The primary metallic phases consisted of elemental nickel crystallites and nickel carbide phases. The kinetic parameters for adsorption and dye photodegradation under UV irradiation were determined and compared to TiO₂-P25. Correlations were found between the adsorption parameters, photocatalytic activity, and nickel content, the pyrolysis method (one-step vs. two-step pyrolysis), and the pyrolysis temperature. The sample with a 1:1:0.25 tannin/Pluronic^®F-127/Ni weight ratio pyrolyzed at 700 °C exhibited the highest photoactivity, achieving rhodamine B degradation rates up to 68 and 2.5 times greater than photolysis and TiO₂-P25. In terms of the normalized weight of the catalysts, it can be concluded that the present Ni-based catalysts are up to two orders of magnitude more photoactive than TiO₂-P25 under UV irradiation, opening a door for indoor UV-driven photoreactors. These findings demonstrate that the EISA method is an effective, low-cost, and ecofriendly approach for synthesizing Ni-decorated carbocatalysts.

The catalytic activity and selectivity of Co-based catalysts supported on home-made nanoporous carbon was studied as a function of the type of alkali promoter (Ca and Mg). The catalysts were characterized by N₂ adsorption/desorption isotherms, temperature-programmed reduction, CO chemisorption, and X-ray diffraction patterns. The catalysts were compared against carbon-supported alkali-promoted Ni-based catalysts and Re-containing catalysts. The catalytic activity of the Co-based catalyst was clearly enhanced in the presence of Ca and Mg, and it was higher than the Ni-based catalysts and comparable to that obtained using an ReC catalyst. The initial activity of the Mg-promoted catalyst increased by a factor of up to 2.5 times higher compared to the non-promoted catalyst. Moreover, this catalyst showed a turnover frequency of up to 5 times higher than equivalent carbon-supported Re-based catalysts. Significant changes were not observed in the selectivity of products after the incorporation of alkali, with cyclohexane being the main product. However, it was demonstrated that the presence of alkali led to a faster and higher production of cyclohexane from the demethoxylation of phenol and the dehydrogenation of cyclohexanol. The present results suggest that Co-based catalysts are an economical alternative for the catalytic conversion of representative target molecules from bio-oil feed.