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Few research has investigated the problem of regeneration of activated carbon once it has been saturated by organic and inorganic contaminants. Among the regeneration methods, electrochemical technology is one of the most advanced, demonstrating its effectiveness in pilot-plant scale experiments using samples obtained from drinking water treatment plants. In the present study, the optimization of a parallel plate electrochemical reactor with a capacity of 15 kg of activated carbon, has been achieved regarding the electrolyte concentration and flow rate. A regeneration efficiency of approximately 90% was achieved with a 0.25 M H2SO4 concentration, while lower concentrations resulted in a voltage exceeding the acceptable limits for this type of installation. In addition, higher flow rates imply a higher recovery of the porous texture of the regenerated activated carbon. This is, to the best of our knowledge, the first report where these two experimental variables are optimized in a pilot-scale process with real saturated activated carbon samples with different types of pollutants adsorbed in the activated carbon.

Solar photocatalytic H2 production has drawn an increasing amount of attention from the scientific community, industry, and society due to its use of green solar energy and a photocatalyst (semiconductor material) to produce green H2. Cu-based semiconductors are interesting as photocatalysts for H2 production because Cu is earth-abundant, cheap, and the synthesis of its copper-containing semiconductors is straightforward. Moreover, Cu-based semiconductors absorb visible light and present an adequate redox potential to perform water splitting reaction. Nevertheless, pristine Cu-based semiconductors exhibit low photoactivity due to the rapid recombination of photo-induced electron-hole (e−-h+) pairs and are subject to photo corrosion. To remedy these pitfalls, the Cu semiconductor-based Z-scheme family (Z-schemes and S-schemes) presents great interest due to the charge carrier mechanism involved. Due to the interest of Z-scheme photocatalysts in this issue, the basic concepts of the Z-scheme focusing on Cu-based semiconductors are addressed to obtain novel systems with high H2 photo-catalytic activity. Focusing on H2 production using Cu-based Z-schemes photocatalyst, the most representative examples are included in the main text. To conclude, an outlook on the future challenges of this topic is addressed.

Nitrogen-doped carbon-based electrodes are among the most promising alternatives to platinum-based electrodes in the cathode of fuel cells and metal-air batteries, where the oxygen reduction reaction (ORR) takes place. Among the approaches for improving ORR activity, nitrogen functionalities and well-developed textural properties have proved very effective. Nonetheless, the question of which between nitrogen active sites or textural properties are more crucial in N-doped carbon materials remains unanswered. This work proposes a comparative and critical approach through the selective functionalization of four commercial activated carbons with different textural properties. This study highlights the greater importance of N-doping in relation to the textural properties of carbon materials, and provides fundamental insights for conclusively addressing the ongoing debate within the carbon community about the significance of these two factors in the context of ORR.

A new and environmentally friendly analytical method for simultaneous determination of As, Cd, Hg and Pb in drug samples by inductively coupled plasma optical emission spectrometry (ICP OES) has been developed. In order to increase the sensitivity of the analysis, a multinebulizer has been used for chemical vapor generation (CVG) after a dispersive liquid-liquid microextraction (DLLME) procedure using a natural deep eutectic solvent (NADES) as extractant solvent. The factors affecting analyte extraction and on-line chemical vapor generation have been optimized by multivariate analysis. Under optimized conditions, DLLME-CVG-ICP OES improved limit of quantitation (LOQ) values on average 50-fold higher compared with direct ICP OES analysis and afforded an increase of the sensitivity (i.e., enrichment factor) on average 25-times higher than those obtained with CVG-ICP OES analysis. According to the United States Pharmacopoeia (USP) Chapter 232, it means LOQ values are on average 4.3-times lower than their respective 0.3J values for the target-elements from class 1. Trueness has been evaluated by recovery experiments following USP recommendations for two oral drug samples in solid dosage form (i.e., commercial dosage tablets). In addition, the greenness of the developed method has been evaluated using the AGREEprep metrics, showing an excellent green character since it includes the miniaturization of the sample preparation procedure using a reduced volume (i.e., few microliters) of a non-hazardous extractant solvent for multielemental analysis.

Bromelains are cysteine peptidases with endopeptidase action (a subfamily of papains), obtained from different parts of vegetable belonging to the Bromeliaceae family. They have some intrinsic medical activity, but this review is focused on their application (individually or mixed with other proteases) to produce bioactive peptides. When compared to other proteases, perhaps due to the fact that they are commercialized as an extract containing several proteases, the hydrolysates produced by this enzyme tends to have higher bioactivities than other common proteases. The peptides and the intensity of their final properties depend on the substrate protein and reaction conditions, being the degree of hydrolysis a determining parameter (but not always positive or negative). The produced peptides may have diverse activities such as antioxidant, antitumoral, antihypertensive or antimicrobial ones, among others or they may be utilized to improve the organoleptic properties of foods and feeds. Evolution of the use of this enzyme in this application is proposed to be based on a more intense direct application of Bromeliaceae extract, without the cost associated to enzyme purification, and the use of immobilized biocatalysts of the enzyme by simplifying the enzyme recovery and reuse, and also making the sequential hydrolysis using diverse proteases possible.

Material synthesis is time- and chemicals-consuming due to the traditional (“brute force”) methodology. For instance, Ni3TeO6 (NTO) is a multiferroic material relevant in different applications. Herein, we used an active learning scheme to explore the different phases obtained using a complex hydrothermal synthesis procedure instead of a solid-state methodology. Different from conventional ML prediction requiring a large dataset, we show that with only 9 data points obtained through experimental endeavor, 87% of the experimental condition space is predicted. The predicted phase configuration is verified with the sample in a new synthetic work. Beside exploring the NTO species, scheme developed herein constitute a powerful tool for experimental condition optimization.

La hibridación de minerales arcillosos con polímeros conductores recibe gran interés por diferentes aplicaciones potenciales, incluida la remediación ambiental. Esta tesis contiene tres partes del estudio, en primer lugar, estudia y compara las propiedades electroquímicas de dos arcillas diferentes, montmorillonita (Mont) y diatomita (Diat), y sus respectivos materiales híbridos arcilla/PEDOT-PSS en medio H2SO4. Los materiales híbridos se prepararon por electropolimerización de EDOT en presencia de PSS. Se analizaron las propiedades físico-químicas y electroquímicas de ambas arcillas mediante diferentes técnicas, y se investigó la influencia de las propiedades de la arcilla en la electropolimerización y la electroactividad de los híbridos arcilla/PEDOT-PSS resultantes. En concreto, la sonda redox Fe2+/Fe3+ y la oxidación de diclofenaco, como contaminante emergente farmacéutico modelo, se utilizaron para probar la capacidad de transferencia de electrones y la respuesta oxidativa, respectivamente, de los híbridos arcilla/PEDOT-PSS. Los resultados demuestran que, a pesar de su baja conductividad eléctrica, el Mont es un material electroactivo en sí mismo con una buena capacidad de transferencia de electrones. Por el contrario, el Diat no muestra electroactividad. La hibridación con PEDOT generalmente mejora la electroactividad de las arcillas, pero las propiedades de la arcilla afectan la eficiencia de electropolimerización y la electroactividad de los híbridos, por lo que Mont/PEDOT muestra propiedades electroquímicas mejoradas. Se demuestra que los híbridos de arcilla/PEDOT-PSS exhiben capacidad de oxidación de diclofenaco y sensibilidad a la concentración de diclofenaco. Se sintetizaron diferentes materiales híbridos a base de arcilla en un solo paso mediante polimerización química de EDOT en presencia de la arcilla sin o con nanofibras de carbono (CNF). Estos materiales fueron caracterizados con diferentes técnicas y estudiados por su potencial aplicación en la rem

Carbon materials constitute a broad family of solids that encompass a high variety of physical and chemical properties, including morphology. These materials have shown to be very useful as catalysts supports and, in this context, also for the heterogenization of metal complexes owing catalytic properties. This work is mainly, the summary of the results obtained in several research projects focused on developing heterogenized molecular catalysts by exploiting the properties of a plethora of carbon materials to address several immobilization procedures.

The sluggish kinetics of the oxygen evolution reaction (OER) is one of the most limiting factors for the development of many “green” electrochemical devices. Expensive ruthenium and iridium oxide electrodes are often used as advanced electrocatalysts to overcome this limitation. However, these materials are rare in nature, which further limit the implementation of this kind of electrochemical device on a global scale. Compounds based on transition metals and boron have proven to be promising alternatives to commercial electrocatalysts due to their high catalytic properties and robust stability under working conditions. However, such compounds are often obtained through expensive synthetic routes that often involve the use of supports, which increases the cost of electrocatalysts. Here, we present an easy and support-free synthesis of bimetallic borates based on the introduction of transition metals into cobalt borates. Depending on the metal, different morphologies, structural order, surface chemistry, and, most importantly, electrocatalytic properties toward the OER have been obtained. Among all the transition metals, nickel is the one that most improves the catalytic activity of cobalt borate for the OER in an alkaline electrolyte. An overpotential of 230 mV, similar to that of commercial and state-of-the-art electrocatalysts, was obtained by using a support-free synthesis route for the preparation of this catalyst.

The transformation of non-edible lignocellulosic biomass into high added-value chemicals and biofuels associated with lower energy process requirements is a promising strategy for meeting the actual demands of clean energy. Here, we report the study of the non-catalytic conversion of biomass wastes issued from two Amazonian abundant fruits (cupuaçu shell and assai stone) into liquid valuable chemicals. The parent biomass samples were first comprehensively characterized using TG, XRD, and FTIR; then, they were pretreated by ball milling and by chemical processing in ionic liquid, and finally, they were hydrothermally treated to be converted into chemical products benefiting from their hemicellulose and cellulose contents. The results revealed the importance of the pretreatments in the conversion rate, while the selectivity into main chemical products (such glucose, HFM, furfural, xylose) is not affected by the pretreatments neither physical nor chemical ones. The conversion of both biomasses and their products’ distribution were comprehensively discussed, with the highest conversion obtained using assai stone biomass (90%). This study could pave the way for investigating the non-catalytic route of biomass conversion, as a lesser energy process, resulting in a cost-effective conversion process.

This work describes the development and characterization of fluorescent nanocomposite hydrogels, with high swelling and absorption capacity, and prepared using a green protocol. These fluorescent materials are obtained by incorporating, for the first time, polyfluorenes-based nanoparticles with different emission bands—poly[9,9-dioctylfluorenyl-2,7-diyl] (PFO) and poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(1,4-benzo-{2,1,3}-thiadiazole)] (F8BT)—into a three-dimensional polymeric network based on polyacrylamide. To this end, two strategies were explored: incorporation of the nanoparticles during the polymerization process (in situ) and embedment after the hydrogel formation (ex situ). The results show that the combination of PFO nanoparticles introduced by the ex situ method provided materials with good storage stability, homogeneity and reproducibility properties, allowing their preservation in the form of xerogel. The fluorescent nanocomposite hydrogels have been tested as a transportable and user-friendly sensing platform. In particular, the ability of these materials to specifically detect the enzyme alkaline phosphatase (ALP) has been evaluated as a proof-of-concept. The sensor was able to quantify the presence of the enzyme in an aqueous sample with a response time of 10 min and LOD of 21 nM. Given these results, we consider that this device shows great potential for quantifying physiological ALP levels as well as enzyme activity in environmental samples.

Introduction: Population-based fecal tests for colorectal cancer (CRC) screening have shown to reduce mortality thanks to the early detection of the disease. However, currently available fecal tests are limited in their sensitivity and specificity. Our aim is to look for volatile organic compounds in fecal samples as biomarkers for CRC detection. Material and Methods: Eighty participants were included; 24 had adenocarcinoma, 24 had adenomatous polyps and 32 presented no neoplasms. Fecal samples were collected 48 h preceding the colonoscopy from all participants, except CRC patient samples that were collected after 3–4 weeks from the colonoscopy. Magnetic headspace adsorptive extraction (Mag-HSAE) followed by thermal desorption-gas chromatography-mass spectrometry (TD-GC–MS) was performed on stool samples to identify volatile organic compounds as biomarkers. Results: p-Cresol was significantly more abundant in the cancer samples (P < 0.001) with an area under the curve (AUC) of 0.85 (CI 95%; 0.737–0.953), having a sensitivity and specificity of 83% and 82%, respectively. In addition, 3(4H)-dibenzofuranone,4a,9b-dihydro-8,9b-dimethyl- (3(4H)-DBZ) was also more abundant in the cancer samples (P < 0.001) with an AUC of 0.77 (CI 95%; 0.635–0.905), sensitivity of 78% and specificity of 75%. When combined (p-cresol and 3(4H)-DBZ), the AUC was 0.86, sensitivity 87% and specificity 79%. p-Cresol also appeared to be promising as a biomarker for pre-malignant lesions with an AUC of 0.69 (CI 95%; 0.534–0.862), sensitivity 83% and specificity 63%, P = 0.045. Conclusions: Volatile organic compounds emitted from feces and determined by a sensitive analytical methodology (Mag-HSAE-TD-GC–MS), employing a magnetic graphene oxide as extractant phase, could be used as a potential screening technology for CRC and pre-malignant lesions.

LaNi1-xCoxO3 perovskite materials were synthesized by a sol-gel method for use in electrochemical reactions which involve molecular oxygen. The metal oxides were characterized by different physicochemical techniques and it was observed that the incorporation of Co induces some changes in the surface of the materials that affect the electrocatalytic activity. The different perovskite metal oxides were mixed with carbon black (Vulcan) to improve their electrocatalytic performance. The results from TPR and TPD techniques supported the XPS interpretation suggesting that a stronger interaction between carbon material and metal oxides can be obtained by physically mixing the two materials. This interaction improves the electron transfer and enhances the catalytic activity. Among the as-prepared materials, it was observed that the electrocatalytic performance of LaNi1-xCoxO3 perovskite/Vulcan materials is higher than that of LaNiO3/Vulcan for ORR, but similar towards OER. It is claimed that Co3+ is more catalytic for ORR, while Ni3+ favors the OER. Moreover, the presence of Co stimulates the formation of chemisorbed oxygen species, which also favor the electron transfer. Metal oxides containing both cations show higher stability, being this effect more notorious for OER. LaNi0.5Co0.5O3/Vulcan seems a suitable bifunctional catalyst for both electrochemical reactions.

A new natural deep eutectic solvent (NADES)-based analytical method for mercury speciation in water samples is presented. A NADES (i.e., decanoic acid:DL-menthol in a molar ratio of 1:2) is used as an environmentally friendly extractant for separation and preconcentration using dispersive liquid–liquid microextraction before LC-UV–Vis. Under optimal extraction conditions (i.e., NADES volume, 50 µL; sample pH, 12; volume of the complexing agent, 100 µL; extraction time, 3 min; centrifugation speed, 3000 rpm; and centrifugation time, 3 min), the limit of detection values were 0.9 µg L−1 for the organomercurial species and 3 µg L−1 for Hg2+, which had a slightly higher value. The relative standard deviation (RSD, n = 6) has been evaluated at two concentration levels (25 and 50 µg L−1) obtaining values for all the mercury complexes within the range of 6–12% and 8–12%, respectively. The trueness of the methodology has been evaluated using five real water samples from four different sources (i.e., tap, river, lake, and wastewater). The recovery tests have been performed in triplicate obtaining relative recoveries between 75 and 118%, with RSD (n = 3) between 1 and 19%, for all the mercury complexes in surface water samples. However, wastewater sample showed a significant matrix effect (recoveries ranged between 45 and 110%), probably due to the high amount of organic matter. Finally, the greenness of the method has also been evaluated by the analytical greenness metric for sample preparation (i.e., AGREEprep).

The interest for the electrodes based on conductive boron-doped diamond powder (BDDP) is increasing in recent years due to their excellent physical and chemical stability, the wide potential window in both aqueous and organic electrolytes, the relatively large specific surface area, and their versatility in comparison to boron-doped diamond thin film electrodes. These materials have been proposed as alternative cathode catalyst support due to their high corrosion resistance when subjected to the highly positive potentials originated during the start-stop operations in fuel cells, especially in automobiles. In this work, we present three BDDP supports with different particle sizes and different surface oxygen contents as supports of different iron species for oxygen reduction reaction in alkaline solution. BDDP supports were modified with carbon nitride (C3N4) or phthalocyanines (Pc) as anchoring points for iron. The different electrocatalytic performance observed confirmed the strong influence of the surface chemistry of the BDDP supports on the activity of the metallic sites for FePc samples while, for Fe-C3N4 samples, the determining effect was the particle size of the BDDP support. Additionally, DFT calculations were used to obtain some insights about the interaction of the FePc with the diamond surface.

Despite great attention toward transition metal tellurates especially M3TeO6 (M = transition metal) in magnetoelectric applications, control on single phasic morphology-oriented growth of these tellurates at the nanoscale is still missing. Herein, a hydrothermal synthesis is performed to synthesize single-phased nanocrystals of two metal tellurates, i.e., Ni3TeO6 (NTO with average particle size ∼37 nm) and Cu3TeO6 (CTO ∼ 140 nm), using NaOH as an additive. This method favors the synthesis of pure NTO and CTO nanoparticles without the incorporation of Na at pH = 7 in MTO crystal structures such as Na2M2TeO6, as it happens in conventional synthesis approaches such as solid-state reaction and/or coprecipitation. Systematic characterization techniques utilizing in-house and synchrotron-based characterization methods for the morphological, structural, electronic, magnetic, and photoconductivity properties of nanomaterials showed the absence of Na in individual particulate single-phase MTO nanocrystals. Prepared MTO nanocrystals also exhibit slightly higher antiferromagnetic interactions (e.g., TN-NTO = 57 K and TN-CTO = 68 K) compared to previously reported MTO single crystals. Interestingly, NTO and CTO show not only a semiconducting nature but also photoconductivity. The proposed design scheme opens the door to any metal tellurates for controllable synthesis toward different applications. Moreover, the photoconductivity results of MTO nanomaterials prepared serve as a preliminary proof of concept for potential application as photodetectors.

SiC is one of the most important ceramics at present due to its excellent properties and wide range of applications. The industrial production method, known as the Acheson method, has not changed in 125 years. Because the synthesis method in the laboratory is completely different, laboratory optimisation may not be extrapolated to the industrial level. In the present study, the results at the industrial level and at the laboratory level of the synthesis of SiC are compared. These results show that it is necessary to make a more detailed analysis of the coke than the traditional one; therefore, the Optical Texture Index (OTI) should be included, as well as the analysis of the metals that form the ashes. It has been found that the main influencing factors are OTI and the presence of Fe and Ni in the ashes. It has been determined that the higher the OTI, as well as the Fe and Ni content, the better the results obtained. Therefore, the use of regular coke is recommended in the industrial synthesis of SiC.

An on-line synthesis of CDots is proposed for the first time, using the flow injection analysis (FIA) technique, which was coupled, in a single system, to the analytical determination of aluminium in water samples. The nanoparticles were obtained from the carbonization of glucose and iron(III) in an acidic medium, and their photoluminescence increased in the presence of aluminium ions. Under optimal experimental conditions, the proposed method has shown an acceptable linearity range –between 0.04 and 3.0 mg L−1 (R2 = 0.9999) – and a detection limit of 0.007 mg L−1. The analysis of drinking water and groundwater samples showed good accuracy (recoveries ranged between 91 – 113%) and RSD% < 13. The on-line system exhibited a high sample throughput (36 h−1), since no incubation time was required.

Carbon-ceramic composites (C/Cer) have been prepared by chemical vapor deposition of coal tar pitch onto clay substrates and characterized by thermogravimetric analyses, powder X-ray diffraction, Raman spectroscopy, and scanning and transmission electron microscopies (SEM and TEM). The study of the dc electrical conductivity, together with the determination of the Hall voltage sign, proves that such C/Cer composites are n-type semiconductors. Our results demonstrate that: 1) the mechanism of electrical conduction of C/Cer semiconductors proceeds through the pathways expected for amorphous solids (ie. variable-range hopping and heat-activated pathways at low and high temperatures, respectively); and 2) their transport properties are strongly dependent on the clay components, as evidenced by microscopy experiments.

Curso que se imparte en la Universidad de Alicante, en el Máster de Ciencias de Materiales.

Metal–organic frameworks (MOFs) are porous hybrid materials with countless potential applications. Most of these rely on their porous structure, tunable composition, and the possibility of incorporating and expanding their functions. Although functionalization of the inner surface of MOF crystals has received considerable attention in recent years, methods to functionalize selectively the outer crystal surface of MOFs are developed to a lesser extent, despite their importance. This article summarizes different types of post-synthetic modifications and possible applications of modified materials such as: catalysis, adsorption, drug delivery, mixed matrix membranes, and stabilization of porous liquids.

Zeolitic imidazolate frameworks (ZIFs) have been profusely used as catalysts for inserting CO2 into organic epoxides (i.e., epichlorohydrin) through cycloaddition. Here, we demonstrate that these materials suffer from irreversible degradation by leaching. To prove this, we performed the reactions and analyzed the final reaction mixtures by elemental analysis and the resulting materials by different microscopies. We found that the difference in catalytic activity between three ZIF-67 and one ZIF-L catalysts was related to the rate at which the materials degraded. Particularly, the {100} facet leaches faster than the others, regardless of the material used. The catalytic activity strongly depended on the amount of leached elements in the liquid phase since these species are extremely active. Our work points to the instability of these materials under relevant reaction conditions and the necessity of additional treatments to improve their stability.

Reverse water gas shift (RWGS) competes with methanation as a direct pathway in the CO2 recycling route, with methanation being a dominant process in the low-temperature window and RWGS at higher temperatures. This work showcases the design of multi-component catalysts for a full-temperature-range RWGS behavior by suppressing the methanation reaction at low temperatures. The addition of alkali promoters (Na, K, and Cs) to the reference Ni/CeO2 catalyst allows identifying a clear trend in RWGS activation promotion in both low- and high-temperature ranges. Our characterization data evidence changes in the electronic, structural, and textural properties of the reference catalyst when promoted with selected dopants. Such modifications are crucial to displaying an advanced RWGS performance. Among the studied promoters, Cs leads to a more substantial impact on the catalytic activity. Beyond the improved CO selectivity, our best performing catalyst maintains high conversion levels for long-term runs in cyclable temperature ranges, showcasing the versatility of this catalyst for different operating conditions. All in all, this work provides an illustrative example of the impact of promoters on fine-tuning the selectivity of a CO2 conversion process, opening new opportunities for CO2 utilization strategies enabled by multi-component catalysts.

Covalent functionalization of multi-walled carbon nanotubes (MWCNTs) and oxidized MWCNTs (o-MWCNTs) with chlorodiphenylphosphine (Ph2PCl) has been studied by cyclic voltammetry in organic medium. Depending the upper potential limit used in the electrochemical functionalization, different amount of phosphorus incorporation n is obtained, as result of the formation of radical species during the electrochemical oxidation of the Ph2PCl. The electrochemical oxidation of Ph2PCl promotes the covalent attachment of diphenylphosphine-like structure on the carbon nanotube surface. At the same time, the incorporation of Cl on the carbon nanotubes is observed during the functionalization. Furthermore, the presence of oxygen surface groups on the MWCNTs provides a favorable attachment of the Ph2P ∙ + species, which has promoted preferentially the formation of C-P bonds, whereas the amount of Cl is reduced.

MXenes are a new family of 2D carbides or nitrides that have attracted attention due to their layered structure, tunable surface groups and high electrical conductivity. Here, we report for the first time that Ti 2 CT x MXene catalyses the selective oxidative dehydrogenation of n -butane to butenes and 1,3-butadiene. This catalyst showed higher intrinsic activity compared to commercial TiC and TiO 2 samples in terms of C 4 olefin formation rate. We propose that the stabilisation of structural vacancies and the change in composition (from a carbide to a mixed phase oxide) in the MXene causes its higher catalytic activity. These vacancies can lead to a higher concentration of unpaired electrons in the MXene-derived material, enhancing its nucleophilic properties and favouring the production of olefins.

Oxygen reduction reaction (ORR) is one of the most important electrochemical reactions for fuel cells. However, commercial Pt-based catalysts used have important limitations such as their deactivation by carbon monoxide and Pt scarcity. In the present work, small and highly-dispersed copper and iron clusters were anchored onto composite supports based on carbon nitride (C3N4) nanostructures and a highly porous carbon material. Catalysts with a moderate carbon nitride content showed an interesting catalytic behaviour because of the combination of the metallic active sites and the availability of micropores, which play an active role in ORR. The presence of either Fe or Cu in the synthesis affected the structure of the resulting composite materials, as well as their electrocatalytic activity. Copper-based materials showed superior catalytic activity, which is supported by the information obtained from the evaluation of the system using DFT computational calculations.

One of the biggest challenges in producing fuel cells at affordable prices is to synthesize carbon materials selectively doped with graphitic nitrogen, as it is considered the most active nitrogen species for the oxygen reduction reaction (ORR). So far, all strategies focus on the use of nitrogen-containing carbon precursors, which limits the functionalization of commercially available carbon materials. Here, we present a post-functionalization method to boost the catalytic properties of carbon materials for the ORR by selectively enriching activated carbons with nitrogen graphitic species. A commercial high-surface area activated carbon was post-functionalized by a two-step procedure. First, the commercial carbon was mixed with different carbon/urea weight ratios and heated in air at 350 °C. Then, the functionalized materials were heat-treated at high temperature (from 700 to 1300 °C) to tailor the amount and distribution of the different nitrogen species in the resulting carbon structure. Nitrogen functionalization using a carbon to urea weight ratio of 1:2 and heat-treatment at 1100 °C led to highly selective doping in graphitic nitrogen species, which provided the tools to individually asses the catalytic activity of these nitrogen species. In addition, this study presents a low-cost and easily feasible synthesis route to improve the catalytic activity of carbon materials, leading to an onset potential of almost 0.9 V compared to reversible hydrogen electrode for ORR in an alkaline electrolyte. Moreover, this study provides significant evidence for the key role of graphitic nitrogen.

Iron(II) phthalocyanines (FePc) supported on functionalized nanostructured carbon materials have been studied as electrocatalysts for the oxygen reduction reaction (ORR) in an alkaline medium. Herein, two types of carbon nanotubes (CNTs) have been explored as support, Single-Walled Carbon Nanotubes and Herringbone Carbon Nanotubes (SWCNTs and hCNTs, respectively), both electrochemically modified with ortho- aminophenylphosphonic acid (2APPA), which provides phosphate axial coordinating ligands for the immobilization of FePc molecules. All the catalysts were prepared via a facile incipient wetness impregnation method. Comprehensive experimental analysis together with density functional theory (DFT) calculations has demonstrated both the importance of the five-coordinated Fe macrocycles that favor the interaction between the FePc and the carbon support, as well as the effect of the CNT structure in the ORR. FePc axial coordination provides a better dispersion, leading to higher stability and a favorable electron redistribution that also tunes the ORR performance by lowering the stability of the reaction intermediates. Interestingly, such improvement occurs with a very low content of metal (∼1 wt% Fe), which is especially remarkable when hCNT support is employed. This work provides a novel strategy for the development of Fe-containing complexes as precious metal-free catalysts towards the ORR.

Electrochemical water splitting requires new, low-cost cathode electrodes for the hydrogen evolution reaction to enable the worldwide implementation of electrolyzers. Cobalt borides are proposed as one of the most promising materials to overcome the limitations of the commercial electrocatalysts, but the catalytic activity still needs to be improved to be competitive. Here, we report that the introduction of zinc into cobalt boride to produce a ternary cobalt boride is an efficient route to further improve the catalytic activity towards the hydrogen evolution reaction (HER) of cobalt boride. The ternary Co-Zn-B was prepared by an easy chemical reduction method to achieve superior HER electrocatalytic performance with a lower overpotential than the homologous Co-B. The larger surface area, structural order, crystallization degree and, in particular, the different surface chemistry seem to be key factors for this improvement.

A series of activated carbon materials have been prepared from petroleum residue using KOH as activating agent. The gravimetric adsorption capacity for methane of the synthesized samples increases with the activation degree, albeit at a lower packing density of the carbon material. These results anticipate an optimum pitch/KOH ratio (1:3) to achieve an upper limit in the volumetric storage capacity. Activated carbon powders have been conformed into monoliths using a small amount of a binder (5 wt%), either carboxymethyl cellulose or polyvinyl alcohol, with proper mechanical properties. Incorporation of graphite or graphene in the initial formulation does not alter and/or modify significantly the textural properties of the original activated carbon. However, once conformed into monoliths, the presence of graphite or graphene allows to improve i) the packing density of the monoliths (up to 0.52 g/cm3), ii) their mechanical properties (compressive strength ≈ 12.3 MPa) and iii) their thermal conductivity (up to 0.49 W/mK) without compromising the methane storage capacity (ca. 100 V/V).

Pepsin is a protease used in many different applications, and in many instances, it is utilized in an immobilized form to prevent contamination of the reaction product. This enzyme has two peculiarities that make its immobilization complex. The first one is related to the poor presence of primary amino groups on its surface (just one Lys and the terminal amino group). The second one is its poor stability at alkaline pH values. Both features make the immobilization of this enzyme to be considered a complicated goal, as most of the immobilization protocols utilize primary amino groups for immobilization. This review presents some of the attempts to get immobilized pepsin biocatalyst and their applications. The high density of anionic groups (Asp and Glu) make the anion exchange of the enzyme simpler, but this makes many of the strategies utilized to immobilize the enzyme (e.g., amino-glutaraldehyde supports) more related to a mixed ion exchange/hydrophobic adsorption than to real covalent immobilization. Finally, we propose some possibilities that can permit not only the covalent immobilization of this enzyme, but also their stabilization via multipoint covalent attachment.

Classrooms at any educational institution have become high-risk sites for contagion during past and present pandemic periods caused by the SARS-CoV-2 (COVID-19) viral siege, given the prolonged time educators and students spend in joint activity. Among the several strategies employed by educational institutions to minimize the outbreak of contagion are regulating classroom capacity and studying the optimal spatial arrangement of students. The architectural features of each classroom, which include corridors, ventilation components, total volume, and maximum capacity, among other factors, have a direct impact on the risk of human contagion. This work is a proposal to optimize the spatial arrangement of students to minimize the risk of contagion, considering not only the distance between them, but also the different architectural features in the classrooms. The analyses conducted in the different scenarios conclude with a comparison of risk in terms of the arrangement of students that various educators would have used at different education levels in their classrooms based solely on intuitive criteria. The results indicate that in some situations, the locations chosen by educators can double the risk of infection compared to optimal arrangements.

We report for the first time the support dependent activity and selectivity of Ni-rich nickel phosphide catalysts for CO2 hydrogenation. New catalysts for CO2 hydrogenation are needed to commercialise the reverse water–gas shift reaction (RWGS) which can feed captured carbon as feedstock for traditionally fossil fuel-based processes, as well as to develop flexible power-to-gas schemes that can synthesise chemicals on demand using surplus renewable energy and captured CO2. Here we show that Ni2P/SiO2 is a highly selective catalyst for RWGS, producing over 80% CO in the full temperature range of 350–750 °C. This indicates a high degree of suppression of the methanation reaction by phosphide formation, as Ni catalysts are known for their high methanation activity. This is shown to not simply be a site blocking effect, but to arise from the formation of a new more active site for RWGS. When supported on Al2O3 or CeAl, the dominant phase of as synthesized catalysts is Ni12P5. These Ni12P5 catalysts behave very differently compared to Ni2P/SiO2, and show activity for methanation at low temperatures with a switchover to RWGS at higher temperatures (reaching or approaching thermodynamic equilibrium behaviour). This switchable activity is interesting for applications where flexibility in distributed chemicals production from captured CO2 can be desirable. Both Ni12P5/Al2O3 and Ni12P5/CeAl show excellent stability over 100 h on stream, where they switch between methanation and RWGS reactions at 50–70% conversion. Catalysts are characterized before and after reactions via X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), temperature-programmed reduction and oxidation (TPR, TPO), Transmission Electron Microscopy (TEM), and BET surface area measurement. After reaction, Ni2P/SiO2 shows the emergence of a crystalline Ni12P5 phase while Ni12P5/Al2O3 and Ni12P5/CeAl both show the crystalline Ni3P phase. While stable activity of the latter catalysts is demonstrated via

Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal for the analysis of liquid samples, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the performances of LIBS towards the analysis of solutions. Among the various strategies, the most promising and versatile appears to be Thin Film Microextraction (TFME) using carbon-based adsorbents. Another sample pre-treatment procedure, Nanoparticle-Enhanced LIBS (NELIBS), has gained significant interest due to its relative simplicity and effectiveness. This methodology uses a deposition of silver nanoparticles (AgNPs) on the sample to greatly increase the emission of the LIBS plasma. In this work, we investigate for the first time the possibility of combining TFME and NELIBS. We developed TFME supports by depositing an aqueous graphene nano-sheets (aq-GRA) prepared by Pulsed Laser Ablation in Liquid (PLAL) on a glass substrate. The preparation of the supports was optimized with regards to the substrate nature, deposition method, sorbent volume and drying method. Then, the TFME supports were tested for the extraction of Chromium from aqueous solution at different extraction times and analyte concentration. Subsequently, the TFME supports were treated with a deposition of silver nanoparticles (AgNP) to test the feasibility of the NELIBS approach. We observed an enhancement in the emission lines of Cr when the AgNPs were applied, as well as a lower estimated LOD value when compared to plain graphene TFME supports.

Esta Tesis Doctoral se ha centrado en la síntesis electroquímica de polímeros conductores basados en polianilina modificada con ácido 2-aminotereftálico y piperazina. Los polímeros sintetizados se han estudiado en la oxidación electroquímica de dopamina y ácido ascórbico y su posible aplicación como sensores electroquímicos a pH fisiológico. Además, se ha estudiado la síntesis química de hidrogeles de los copolímeros desarrollados, se han caracterizado con diferentes técnias y se ha estudiado su aplicación como electrodos en supercondensadores.

Recent advances in cellular materials for active thermal management applications involve the integral design of their porous structure. In this work, open-cell aluminum foams with porosities in the range of 0.60–0.76 are developed, containing pores with spherical geometry and a bimodal pore size distribution. The fabrication strategy involves the use of the replication method by infiltration with liquid aluminum of porous preforms formed by packing NaCl spheres of two largely different sizes (7 mm and 1 mm average diameter), which are then removed by water dissolution. The paper describes cellular materials with different proportions of coarse and fine pores. Their detailed characterization by pore volume fraction, pressure drop, permeability, thermal conductivity and heat transfer coefficient is supported by analytical schemes. In addition, these materials were characterized under realistic operating conditions using computational fluid dynamics simulations. The material with 67 percent coarse pores and 33 percent fine pores, which has the highest porosity (and thus permeability), has the most appealing heat dissipation properties with the lowest pressure drops, making it an excellent candidate for emerging thermal management applications in electronic systems.

The synthesis of methanol by carbon dioxide hydrogenation has been studied using copper-molybdenum carbides supported on high surface area graphite, reduced graphene oxide and carbon nanotubes. The synthesis conditions and the effect of the support were studied. The catalysts were prepared in situ using H2 or He at 600 °C or 700 °C. Both molybdenum carbide and oxycarbide were obtained. A support with less reactive carbon resulted in lower proportion of carbide obtained. The best results were achieved over a 5 wt.% Cu and 10 wt.% Mo on high surface area graphite that reached 96.3% selectivity to methanol.

Se analiza un conjunto de tres discos de cerámica procedentes de los niveles del Hierro Antiguo de Peña Negra. Presentan diferentes acabados y estarían provistos de asas, por lo que deben interpretarse como tapaderas de grandes recipientes de almacenaje. Se ha realizado el estudio petrográfico y mineralógico mediante microdifracción de rayos X (µDRX). Los resultados indican que se trata de piezas de composición relativamente homogénea y de probable producción local, cocidas a baja temperatura. Se revisa el hallazgo de objetos similares en otros contextos del Hierro Antiguo, destacando los recuperados en el Noreste peninsular y el Valle del Ebro, donde además se localizan discos-tapadera realizados en yeso similares a dos ejemplares recuperados en Peña Negra, donde es un material frecuente empleado en la construcción y en la fabricación de objetos., A set of three ceramic discs from the Early Iron Age levels of Peña Negra are analysed. They exhibit differences in surface treatment and would have been fitted with handles, so they should be interpreted as lids of large storage vessels. Samples of each disc were studied by means of petrographic and mineralogical analysis (X-ray micro-diffraction, µDRX). Resulting data indicate that those are pieces of relatively homogeneous composition and that were probably locally produced, fired at low temperatures. The discovery of similar objects in other Early Iron Age contexts is reviewed, highlighting those recovered in the Northeast of the Iberian Peninsula and the Ebro Valley, where gypsum discs have also been found, similar to two examples found in Peña Negra. In this site, gypsum was commonly used as raw material in building activities and other crafts.

A series of activated carbon materials have been successfully prepared from a non-essential amino acid, such as L-cysteine. The synthesized carbons combine a widely developed porous structure (BET surface area up to 1000 m2/g) and a rich surface chemistry (mainly oxygen, nitrogen and sulphur functionalities). These surface functional groups are relatively stable even after a high temperature thermal treatment (O>N∼S). Experimental results show that these samples with a rich surface chemistry exhibit a significant improvement in their hydrophilic character. Although the role of the surface functional groups is less pronounced for the adsorption of non-polar molecules such as CO2, CH4 and C2H4, their adsorption at atmospheric pressure is to some extend conditioned by the characteristics of the adsorbent-adsorbate interactions. The synthesized carbons exhibit an excellent adsorption performance for CO2 (up to 3 mmol/g at 0°C). Furthermore, samples with a low activation degree exhibit molecular sieving properties with very promising CO2/CH4 (up to 4.5) and C2H4/CH4 (up to 6) selectivity ratios. These results anticipate that non-essential amino acids are a versatile platform to obtain carbon materials combining a tailored porous structure and rich multifunctional surface chemistry and with potential application for gas adsorption/separation processes.

This paper provides the basis for understanding the preparation and properties of an old, but advanced material: activated carbon. The activated carbons discussed herein are obtained from “green” precursors: biomass residues. Accordingly, the present study starts analyzing the components of biomass residues, such as cellulose, hemicellulose, and lignin, and the features that make them suitable raw materials for preparing activated carbons. The physicochemical transformations of these components during their heat treatment that lead to the development of a carbonized material, a biochar, are also considered. The influence of the chemical activation experimental conditions on the yield and porosity development of the final activated carbons are revised as well, and compared with those for physical activation, highlighting the physicochemical interactions between the activating agents and the lignocellulosic components. This review incorporates a comprehensive discussion about the surface chemistry that can be developed as a result of chemical activation and compiles some results related to the mechanical properties and conformation of activated carbons, scarcely analyzed in most published papers. Finally, economic, and environmental issues involved in the large-scale preparation of activated carbons by chemical activation of lignocellulosic precursors are commented on as well.

Herein, it has been developed a method to prepare metallic foams starting from Zamak5 (ZnAlCu alloy) with different pore sizes. The Zamak5 metallic foam is designed to serve as a support and metallic precursor of ZIF-8. In this way, composite materials MOF-metal can be prepared, these composites have a large number of application in energy exchange processe such as: adsorption or chemical reactions. Additionally, this method of sythesizing MOFs is environmentally friendly thanks to absence of solvents. Hanerssing the low melting point of the linker, the linker is infiltrated into the foam where the foam and the linker react to form the ZIF-8. In this way we have managed to transform part of the foam into ZIF-8 crystals that remain adhered to the foam. The foams have been characterized and modeled studying the mechanical and electrical properties, finding that both can be predected by various models. Among these, Ashby and Mortensen models for mechanical properties and Ashby and Percolation model for electrical properties stand.

METland® technology consists of a bioengineering strategy for treating wastewater by integrating microbial electrochemical concepts into constructed wetland systems to enhance pollutants removal. In this context, we have constructed planted (Iris sibirica) biofilters to assess the impact of different electrically conductive bed materials (electroconductive coke, electroconductive biochar, non-electroconductive biochar and gravel) by analyzing the (i) wastewater treatment efficiency (COD and nitrogen removal), (ii) bioelectrochemical response, and (iii) diversity of microbial communities. Electrically conductive materials outperformed non-conductive ones allowing removal rates as high as 175-180 gCOD/bed*m3 day capable to support footprint as low 0.4 m2/pe. In contrast, the highest nitrogen removal rates were achieved with non-conductive biochar in presence of plants (80 %) regardless the anoxic conditions of the assay. This was confirmed by the presence of annamox bacteria like Planctomycetes. Furthermore, the presence of a marked electric potential profile along the bed height in electroconductive materials together with redox pairs (cyclic voltammetry analysis) demonstrated an effective electron flow from bottom to uppermost layers of the bed (geoconductor mechanism). In electroconductive biochar, such effective conductivity-based model co-exists with a geobattery mechanism due to presence of electroactive phenolic and carbonyl/quinone groups and/or microporosity. Microbial biodiversity analysis revealed the impact of plants just at the upper layers of the biofilters where roots and Rhizobium predominate. Bacteria from genus Clostridium were dominant in gravel inert material; in contrast, bacteria from genus Geobacter (12%) and Trichococcus (30%) outcompete the rest of communities for an effective colonization of carbonaceous beds, suggesting their main role as part of the electrosyntrophies mechanism after METland®.

Guefoams (guest-containing foams) are a new-class of open-cell cellular materials that extend the properties of conventional foams by incorporating guest phases that convert them into multifunctional materials. This manuscript describes the development of pitch-derived composite guefoams that contain two types of inclusions: iron nanoparticles embedded in the cellular skeleton and activated carbon particles as guest phases. The activated carbon particles significantly increase the specific surface area and gas adsorption capacity. When these materials are exposed to low-intensity magnetic fields, the iron nanoparticles confer a high magneto-inductive capacity that enables ultrafast heating and rapid desorption of adsorbed species. The ability of these materials to act as preconcentrators for volatile organic compounds (VOCs) is demonstrated in this work using toluene as a proof of concept. The Guefoams developed here have greater preconcentration capabilities than current state-of-the-art systems while also being significantly more energy efficient due to the magnetic induction controlled desorption process. This unparalleled blend of properties makes these guefoams a valuable tool for energy-efficient VOCs management.

La experiencia docente descrita en este trabajo trata sobre el aprendizaje asíncrono sobre medio ambiente y energías sostenibles mediante el uso de una herramienta en línea. Para llevar a cabo dicha experiencia, se preparó un curso mediante la plataforma Moodle, el cual estaba dividido en 4 bloques temáticos ((I) El Cambio Climático: Una Realidad Cotidiana; (II) Energías Sostenibles; (III) Almacenamiento de Energía Sostenible; (IV) El Camino hacia la Sostenibilidad), cada uno de los cuales estaba formado por una serie de diapositivas con el contenido teórico, acompañado de una introducción audiovisual y material complementario que permitía al alumnado profundizar en los temas abordados. Además, al final del curso el alumnado debía contestar a un cuestionario sobre el contenido teórico del mismo y a una encuesta que recababa su opinión sobre el empleo de entornos de aprendizaje virtual asíncrono. Los resultados obtenidos pusieron de manifiesto el interés del alumnado por el empleo de dichos entornos de aprendizaje y el gran potencial de los mismos, los cuales están en línea con los intereses de las nuevas generaciones.

Formic acid has been postulated as one of the most promising liquid organic hydrogen carriers. Numerous studies dealing with the development of efficient catalysts able to boost the dehydrogenation of formic acid can be found in recent literature. However, most of them lack in stability, so that finding stable catalysts is highly desirable yet challenging. In the present study, we developed Pd-based biomass-derived carbon-supported catalysts by following a simple protocol. The effect of the modification of both the metal phase and support has been assessed by incorporating Ag in the form of bimetallic nanoparticles and nitrogen functional groups, respectively. The effect of the method followed for the preparation of the catalysts was also checked. It has been found that the resulting PdAg-based catalysts supported on N-doped biomass-derived carbon materials showed suitable activity and excellent stability under reaction conditions. The present study highlights the potential of modulating the features of the catalysts, not only in terms of the composition of the metal phase and incorporation of heteroatoms in the support, but also in terms of the synthetic protocol used.

Nowadays one of the biggest challenges for carbon materials is their use in CO2 capture and their use as electrocatalysts in the oxygen reduction reaction (ORR). In both cases, it is necessary to dope the carbon with nitrogen species. Conventional methods to prepare nitrogen doped carbons such as melamine carbonization or NH3 treatment generate nitrogen doped carbons with insufficient nitrogen content. In the present research, a series of activated carbons derived from MOFs (ZIF-8, ZIF-67) are presented. Activated carbons have been prepared in a single step, by pyrolysis of the MOF in an inert atmosphere, between 600 and 1000 °C. The carbons have a nitrogen content up to 20 at.% and a surface area up to 1000 m2/g. The presence of this nitrogen as pyridine or pyrrolic groups, and as quaternary nitrogen are responsible for the great adsorption capacity of CO2, especially the first two. The presence of Zn and Co generates very different carbonaceous structures. Zn generates a greater porosity development, which makes the doped carbons ideal for CO2 capture. Co generates more graphitized doped carbons, which make them suitable for their use in electrochemistry.

Manganese-based materials can catalyze the oxygen reduction reaction (ORR), although their activity is known to depend on the crystalline phases and on the concentration of surface-active species. In the present study, we have optimized these two parameters to obtain improved catalysts for ORR. A sol-gel method was used to synthesize LaMnO3-manganese oxides composites with different lanthanum-to-manganese atomic ratios. The synthesized materials, which can be described as La1-xMnOz, were tested under ORR conditions and characterized by several physicochemical techniques such as SEM, XPS, EDX or XRD. It was found that the concentration of lanthanum governs the formation of different crystal phases and determines the crystallite size. Besides, high values of x tend to increase the surface concentration of manganese and therefore to produce more active sites for ORR. Among the materials analysed, La0.6MnOz mixed with carbon black (Vulcan) showed the best electrocatalytic performance. The high tolerance to methanol makes this electrocatalyst a promising alternative to substitute Pt-based materials in alkaline electrolytes.

In this study, we synthesized MnFe2O4 solid nanospheres (MSN) calcined at different temperatures (200–500 °C) and MSN-based materials mixed with carbon black, for their use as electrocatalysts in the oxygen reduction reaction (ORR) in alkaline medium (0.1 M KOH). It was demonstrated that the calcination temperature of MSN material determined its chemical surface composition and microstructure and it had an important effect on the electrocatalytic properties for ORR, which in turn was reflected in the performance of MSN/CB-based electrocatalysts. The study revealed that the presence of Mn species plays a key role in the ORR activity. Among tested, MSN200/CB and MSN350/CB exhibited the best electrochemical performances together with outstanding stability.

Poisoning tolerance of Pt-based catalyst is an important parameter for the designing of direct electrochemical fuel cells (EFCs) based on electrooxidation of alcohols (i.e. methanol, ethanol). Applicability of direct ethanol EFCs is still challenging taking into account the lack of effective electrocatalysts which are able to produce high faradic current densities and high stability towards strong adsorption of C1 and C2 oxidation products. As we present here, mono- and bimetallic Pt-based electrocatalysts have been synthesized on a carbon black support for the elecotrooxidation of ethanol in acidic media. Depending of the molar ratio between poly-n-vinylpyrrolidone (PVP, acting as protecting agent) and Pt, nanoparticle size distribution has been controlled, obtaining an optimal condition of Pt loading and electroactive surface area (ECSA) for the PVP/Pt ratio = 1. The electrochemical behavior of electrocatalyst Pt/Re/CB-1 shows a negligible variation in the ECSA (98.3 m2 g−1) in comparison with the monometallic electrodes (90.2 m2 g−1). In contrast, addition of Ir tends to reduce the ECSA by agglomeration of some nanoparticles and decreasing its electrochemical performance. Incorporation of Re in the alloy promotes bond breaking of the intermediates adsorbed on surface, specifically adsorbed C2 molecules, releasing great number of the active sites from the Pt surface, minimizing the deactivation with cycling and providing remarkable stable catalyst with high specific current densities with the addition of small amounts of Re.