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Proton exchange membrane water electrolysis is widely used in hydrogen production, but its application is limited by significant electrocatalyst dissolution at the anode during the oxygen evolution reaction (OER). The best performing electrocatalysts to date are based on ruthenium and iridium oxides, but these experience degradation even at moderate cell potentials. Here we investigate a quaternary Sn-Sb-Mo-W mixed oxide as a protective scaffold for ruthenium oxide. The acid-stable mixed oxide consists of an interconnected network of nanostructured oxides capable of stabilizing ruthenium into the matrix (Ru-MO). In combination with titanium fibre felt, we observed a lower degradation in the oxygen evolution reaction activity compared to unprotected ruthenium oxide after the electrochemical stress test. The superior stability of Ru-MO@Ti is attributed to the presence of MO which hinders the formation of reactive higher valence ruthenium (Ru+8). Our work demonstrates the potential of multi-metal oxides to extend the lifetime of the OER active metal and the titanium support.

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Nitrosoamines (NAms), methanol and furfural are toxic compounds that are frequently found in low concentrations in alcoholic beverages and food products. NAms such as Nitrosodimethylamine, Nitrosodiethylamine, Nitrosodibutylamine, Nitrosopiperidine and Nitrosopyrrolidine are considered cancerogenic and mutagenic compounds whereas furfural and methanol can lead in skin cancer and eye damage respectively. Therefore, in this work these compounds were analyzed in tequila (white, rested and aged), which is an important and highly consumed beverage. The technique of headspace solid-phase micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used for its simplicity, speed, high precision and its environmental friendliness. The influence of the important extraction parameters such as temperature (Teq), equilibrium time (teq), extraction time and ionic strength was evaluated through a factorial analysis. The quantification was carried out using the standard additions method. In order to validate the methodology, the limits of detection and quantification were determined. Amongst the NAms, the NDBA was the only NAm detected in all the tequila samples studied. The maximum concentrations found of NDBA, furfural and methanol were 7.33 µg/L, 0.95 mg/100 mL anhydrous alcohol and 132.51 mg/100 mL anhydrous alcohol. These amounts were within the limits considered safe for human consumption by the Environmental Protection Agency and Mexican norms.

Furfural is a toxic compound that can be found in a wide variety of everyday food and beverages, notably espresso coffee. Given the toxicity of furfural, exposure could lead to liver and skin cancer. Recently, graphene oxide (GO) has been used for application in Solid Phase Micro-Extraction (SPME) due to its large surface area and wide variety of oxygenated functional groups, which makes it an excellent support for the adsorption of different organic compounds. Therefore, in this work a thermally reduced graphene oxide coating (rGOC) was synthetized for the micro-extraction of furfural in espresso coffee. This rGOC was able to absorb the furfural from espresso coffee despite having thickness of around only 1.9 μm. An analysis and optimization of extraction conditions of the furfural in the espresso coffee was carried out and then applied to the quantification of furfural. The furfural was quantified using a Gas Chromatograph coupled to a Mass Spectrometer (GC–MS). The concentration of furfural found was 2.1724 ± 0.0837 mg/L using rGOC whereas with commercial DVB/CAR/PDMS fiber was 2.0766 ± 0.0444 mg/L. The present work attempts to expand the applications of GO in SPME through the analysis of furfural in complex matrix foodstuffs such as espresso coffee. The application of rGOC, as presented in this article, has the advantage of being easy to prepare, requires a low quantity of material and together with its low cost, such application can easily be used instead of commercial fibers.

Graphene oxide (GO) is a carbon material with wide chemistry, and its functionalization represents the main challenge to develop multi-functional materials for different applications. Besides to epoxide and carboxyl groups, the alkenes that arise during the graphite oxidation seem to provide an excellent approach for developing selective reactions. In specific, α,β-unsaturated acids can be functionalized by thiol-ene Michael addition (TEMA) using base catalysts. However, when base catalysts are used, the thiol-epoxide ring opening reaction (TEROR) has been considered as the predominant and unique reaction. Therefore, there is a need to understand the reactivity of the GO when TEMA and TEROR take place from a qualitative and quantitative point of view. Herein, we studied the functionalization of GO and reduced graphene oxide (RGO) with cysteamine (CA) using different base catalysts. XPS results revealed that despite the thermal reduction of GO, the functionalization was possible confirming the coupling reaction between the CA and α,β-unsaturated acids of RGO by TEMA. In addition, a quantitative analysis was conducted via fluorescent labelling corroborating that TEMA produced more CA molecules bonded to GO than TEROR.

The synthesis of electrochemically active β-Mo2C nanoparticles for hydrogen production was achieved by a fast and energy-efficient microwave-assisted carburization process from molybdenum oxides and carbon black. With the use of microwave-based production methods, we aim to reduce the long-time high-temperature treatments and the use of hazardous gases often seen in traditional molybdenum carbide synthesis processes. In our process, carbon black not only serves as a carbon source but also as a susceptor (microwave absorber) and conductive substrate. The irradiation power, reaction time, and Mo:C ratio were optimized to achieve the highest electrocatalytic performance toward hydrogen production in an acidic electrolyte. A complete transformation of MoO3 to β-Mo2C nanoparticles and an additional graphitization of the carbon black matrix were achieved at 1000 W, 600 s, and Mo:C ratio above 1:7.5. Under these conditions, the optimized composite exhibited an excellent HER performance (η10 = 156 mV, Tafel slope of 53 mV·dec-1) and large turnover frequency per active site (3.09 H2·s-1 at an overpotential of 200 mV), making it among the most efficient non-noble-metal catalysts. The excellent activity was achieved thanks to the abundance of β-Mo2C nanoparticles, the intimate nanoparticle-substrate interface, and enhanced electron transport toward the carbon black matrix. We also investigated the flexibility of the synthesis method by adding additional Fe or V as secondary transition metals, as well as the effect of the substrate.

Graphene oxide (GO) is an important platform that can be functionalized due notably to its wide variety of functional groups. The functionalization is a critical step leading the production of GO b...

Graphene oxide is widely-used for many applications because of its surface area and the variety of oxygen functional groups that possess. This latter feature allows it to be a good candidate for polar compounds adsorption such as furfural. Furfural is a toxic compound that has been detected in a wide variety of foods of daily consumption. Frequent exposure in high doses can represent a risk to human health. In the present work, it is proposed an easy procedure to obtain reduced graphene oxide based coatings through dip-coating for Solid Phase Micro-Extraction (SPME) of furfural. The coatings were made with graphene oxide and carboxylated graphene oxide. These coatings were thermally reduced and then tested using a furfural standard. The thermally reduced graphene oxide coatings were characterized using FT-IR, Raman spectroscopy and SEM. SEM micrographs revealed that graphene oxide based fibers had thickness values between 1.5 and 2.5 μm approximately. Subsequently the results of furfural extraction were compared with those obtained from the Divinylbenzene/Carboxen/Polydimethylsiloxane (DVB/CAR/PDMS) commercial fibers.

Amino acids are important compounds for GO functionalization because they can improve GO properties for many applications ranging from biomedicine to depollution. However, amino acids can act as nucleophiles or as reducing agents for GO functionalization or reduction, respectively. Hence, we systematically studied the GO functionalization/reduction using glycine as a model amino acid under basic conditions at room temperature. Attenuated total reflectance–Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy, and Raman spectroscopy were used to characterize the modified GO with glycine. We found that low glycine concentrations produced an epoxide ring opening reaction, whereas an increase in glycine concentration led to GO reduction. The basic medium allowed to conserve the carboxylic acid groups, whereas the GO reduction mechanism was governed by the partial hydrolysis of epoxide groups and the subsequent reduction of carboxylic acids to carbonyls. This article opens up the opportunity to study and control the conditions in which different amino acids could be used for either GO functionalization or GO reduction.