Ulises León-Silva

TiO₂-based photocatalysts modified with CuO and co-doped with Fe, Zn, and hydroxyapatite (HA) were evaluated for the simultaneous production of H₂ and the decolorization of Acid Black 1 (AB1). Under anodic galvanostatic operation in a neutral medium, ternary materials followed second-order kinetics, with Zn-Cu-TiO₂ exhibiting the highest rate constant (k = 0.0064 L/mg*min), while binary systems followed first-order kinetics and HA₆₀₀-TiO₂ showed the best performance. Under these conditions, H₂ production was negligible. Under cathodic operation, both galvanostatic and potentiostatic modes led to first-order decolorization kinetics. The best performance was achieved in an alkaline medium under potentiostatic operation at −120 mV vs. Ag/Agcl, using Zn-Cu-TiO₂, reaching a rate constant of 0.11 min⁻¹, a maximum dissolved H₂ concentration of approximately 1810 ppb, and a cumulative H₂ production of 37,093 ppb/g_catalyst within 30 min, while maintaining more than 90% AB1 decolorization. In addition, an initial AB1 concentration of 25 mg·L⁻¹ favored both hydrogen production and dye removal. These results identify Zn-Cu-TiO₂ as the most promising photocatalyst for integrating wastewater remediation with sustainable hydrogen generation, particularly under cathodic potentiostatic operation in an alkaline medium.

The current global warming is driving the use of clean and renewable energy. Intermittence is a drawback of clean energy. Energy storage is the answer to intermittence. Flow batteries, batteries, capacitors, and supercapacitors are among the most used energy storage devices in the world. In this paper, capacitors made from graphite and commercial graphene were fabricated. The obtained specific capacitances reached 851 F g ⁻¹ , indicating that the devices meet the performance standard for supercapacitors. The devices were fabricated using cellulose nanocrystals as binding material in the electrode, thus using an environmentally friendly binding material. Cyclic voltammetry revealed a quasi‐rectangular process. Charge–discharge cycles revealed a storage mechanism of electrical double layer. The Warburg impedance indicates the diffusive impedance of electrolyte ions in the devices.

Carbon steel, bronze and aluminum alloys presents excellent properties such as strength, durability, malleability, ductility, heat and electricity conduction, among others. However, these materials are prone to severe corrosion in some aqueous media and there are few methods to determine the quality according to corrosion rate in a simple manner. In this study, a novel method based on hyperspectral imaging (HSI) in the range of 400 to 650 nm was proposed for the characterization of the corrosion degree in A36 carbon steel, C844 bronze and 6063 aluminum alloys after immersion in basic, neutral and acidic aqueous solutions for 480 h; the corrosion rate was correlated with characteristic hyperspectral response. The results showed that the change in the spectral characteristic response of the corroded samples reflected the severity of corrosion, which was confirmed by comparing the corrosion rates obtained in the weight loss test.

Corrosion monitoring is essential to assess the integrity of metal structures and prevent critical failures. Corrosion increased in coastal areas by the chemical reaction between moisture and sodium chloride. Because of this, different techniques have been developed for monitoring and contributing to the integrity in metal structures. However, more effort is needed to assess structural integrity in different industries. In this work, a tapered optical fiber sensor for monitoring corrosion processes in the X70 pipeline steel immersed in natural seawater is proposed and experimentally demonstrated. A DC electrochemical test was carried out to obtain potentiodynamic polarization curves, which are associated with different corrosion processes occurring in the metal samples at different electrode potentials. The fabrication process of the tapered optical fibers consisted mainly of heating the fiber with a flame and stretching it. The operating principle of the sensor was based on the interaction of the evanescent wave with corrosion products dissolved in seawater at 50 °C. The fiber optic sensor response was related to regions of the potentiodynamic polarization curve of X70-PS in seawater at 50 °C. Therefore, from 0.12 to 0.0285 μW correspond to the anodic and cathodic regions at potentials of the electrode between −2 and −0.5 V and −0.5 and 1 V, respectively. Moreover, this optical response could be correlated with some corrosion processes experienced by the metallic samples such as pre-passivation and passivation.

Sargassum has become an “ecological disaster” on most beaches in the Caribbean Sea, causing serious health, safety, economic and environmental problems. The objective of this study was to valorize sargassum for the extraction of sodium alginate, cellulose and cellulose nanocrystals. Cellulose was also used in the manufacture of a separator for an energy storage device (ESD) based on expanded graphite and activated carbon. Sargassum was characterized physicochemically; the results of this characterization are very relevant for the generation of bioenergy and removal of toxic contaminants. The extracted materials were identified by FT-IR; the spectra were very similar to the IR spectra of commercial samples, which corroborated that the materials extracted were sodium alginate, cellulose and cellulose nanocrystals. The performance of the ESD/cellulose-based separator was determined using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Additionally, an RC circuit and an oscilloscope were used to perform a charge/discharge test. The voltammograms obtained for the ESD showed a rectangular shape with redox peaks characteristic of a pseudocapacitor and a battery, and the Nyquist plot showed a typical electrochemical performance of such ESD. Likewise, the developed devices have the capacity to store and release energy in seconds.

Cellulose nanocrystals (CNCs) are a very versatile material, and optimizing the reaction conditions to obtain them is vital for cost savings, purity, selectivity, or performance. In this study, the reaction conditions of the CNCs were tested, as well as their application as binders for the fabrication of electrodes of a symmetric capacitor (based on activated carbon). The resulting CNCs were physicochemically characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, atomic force microscopy, and its capacitive properties using cyclic voltammetry (CV). It was found that the best reaction conditions were at 45°C, 30 and 45 minutes, and 64 wt%. The CNCs were used as a binder, as they conferred stability to the electrodes and prevented the crumbling of the activated carbon electrodes. The CV measurements showed a capacitor behavior; CNCs can be used in energy storage applications.

The design of new materials with two or more functional groups must be strongly considered to achieve multifunctional coatings with outstanding properties such as active-passive protection against corrosion, low-friction, antifouling, sensing, among others. In this sense, nanocomposites based on solvent-free epoxy resin/bi-functionalized-reduced graphene oxide layers with NH₂ and NH₃⁺ groups (Epoxy Resin/BFRGO) with super-anticorrosive properties are for the first time reported here. The amine groups (-NH₂) act as crosslinker agents, which react with epoxy terminal groups from resin, thus closing the gap between the BFRGO layers and the polymeric matrix. Meanwhile, the ammonium ions (-NH₃⁺) are effective trapping agents of atoms or molecules negatively-charged (e.g., Cl^-). This novel combination promotes to get nanocomposite coatings with passive-active protection against corrosion. Epoxy Resin/BFRGO deposited onto A36 mild steel exhibited a remarkably enhanced barrier against corrosion into a saline medium (1M NaCl:58.4 g/L), wherein the corrosion current density (icorr) was diminished six orders of magnitude (icorr = 5.12 E^-12 A/cm²), with respect to A36 mild steel coated only with Epoxy Resin (icorr = 2.34 E^-06 A/cm²). Also, the highest polarization resistance R_p = 6.04 E⁺⁰⁷ Ω/cm² was obtained, which represents the lowest corrosion rate and corresponds to three orders of magnitude higher than A36 mild steel coated with Epoxy Resin (R_p = 1.43 E⁺⁰⁴ Ω/cm²). The strategy of bi-functionalization proposed herein to get bi-functionalized-reduced GO with NH₂ and NH₃⁺ groups has not been disclosed in the literature before, in consequence, this work opens a new pathway towards the design of smart materials based on multifunctional nanomaterials.

The rise for innovation in the electrical industry is strongly driven by development of new materials. Features of new materials are changing design paradigms for engineers. In this paper, the electrical properties of films of cellulose nanocrystals were measured. It was found that humidity affects the dielectric strength on the cellulose nanocrystals (CNCs). The dielectric strength was similar to the value of the industrial dielectric paper. The addition of plasticizer improved the flexibility of the material but lowered the dielectric strength. The films of CNC had an ordered arrangement, as suggested by the iridescence shown by them. The humidity content of the films was measured by thermogravimetric analysis. The CNC film was used for assembling a capacitor and compared to a capacitor assembled with dielectric paper.