Nicola Melis

Cu-Ni co-deposit electrodes were prepared and tested in an undivided cell for the electrochemical removal of nitrate from aqueous solutions. Pulsed electrodeposition (PED) under a dynamic hydrogen bubble template and direct electrodeposition (DE) techniques were used for synthetizing porous nickel- and copper-based cathodes. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analyses showed dendritic and cauliflower-like deposits with a uniform distribution of nickel and copper on the electrode surface, both using flat and foam nickel supports. The PED technique on nickel foam generated highly porous Cu-Ni coatings, with the largest electrochemical active surface area (ECSA) among all the investigated electrodes. Electrolysis in alkaline solutions containing nitrates was performed in an undivided cell in potentiostatic mode. The selectivity towards N₂ was strongly dependent on both copper loading and applied potential; in particular, the foam electrode containing about 23% Cu showed very low ammonia production even at the highest cathodic overpotential, evidencing its marked preference for nitrogen formation. The process performed in the undivided cell using foam-supported Cu-Ni cathodes enabled 100% of conversion of nitrate to molecular nitrogen within approximately 7 h, allowing the complete denitrification of the water.

Hydrogen production technologies are undergoing rapid diversification, driven by the dual imperative of decarbonization and resource circularity. While conventional water electrolysis, particularly PEM and alkaline systems, represents a mature and scalable solution for centralized hydrogen generation, biologically mediated pathways such as microbial electrolysis cells (MECs), dark fermentation, and anaerobic digestion are gaining visibility as decentralized, low-energy alternatives. This review presents a bibliometric analysis of hydrogen research from 2021 to 2026, based on three multi-query strategies that retrieved 6017 works in MQ1, 7551 works in MQ2, and 1930 works in MQ3. The year 2026 is included in the dataset because Scopus indexes articles already accepted and released in early access, assigning them their forthcoming official publication year. Keyword co-occurrence mapping using VOSviewer highlights thematic clusters and disciplinary shifts. The results reveal a strong dominance of electrochemical research, with biohydrogen production emerging as a distinct but less mature frontier rooted in biotechnology and environmental science. MECs, in particular, occupy a transitional zone between electrochemical and biological paradigms, offering multifunctional platforms for simultaneous waste valorization and hydrogen generation. However, their low Technology Readiness Levels (TRLs) and unresolved engineering challenges limit their current scalability. The comparative analysis of bibliometric queries underscores the importance of integrating electrochemical and biotechnological approaches to build a resilient and context-adaptive hydrogen economy. This study provides a structured overview of the evolving knowledge landscape and identifies key directions for future interdisciplinary research and innovation.

The potential of aerogels as catalysts for the synthesis of a relevant class of bis-heterocyclic compounds such as bis(indolyl)methanes was investigated. In particular, the studied catalyst was a nanocomposite aerogel based on nanocrystalline nickel ferrite (NiFe₂O₄) dispersed on amorphous porous silica aerogel obtained by two-step sol–gel synthesis followed by gel drying under supercritical conditions and calcination treatments. It was found that the NiFe₂O₄/SiO₂ aerogel is an active catalyst for the selected reaction, enabling high conversions at room temperature, and it proved to be active for three repeated runs. The catalytic activity can be ascribed to both the textural and acidic features of the silica matrix and of the nanocrystalline ferrite. In addition, ferrite nanocrystals provide functionality for magnetic recovery of the catalyst from the crude mixture, enabling time-effective separation from the reaction environment. Evidence of the retention of species involved in the reaction into the catalyst is also pointed out, likely due to the porosity of the aerogel together with the affinity of some species towards the silica matrix. Our work contributes to the study of aerogels as catalysts for organic reactions by demonstrating their potential as well as limitations for the room-temperature synthesis of bis(indolyl)methanes.

Nanoporous (NP) gold, the most extensively studied and efficient NP metal, possesses exceptional properties that make it highly attractive for advanced technological applications. Notably, its remarkable catalytic properties in various significant reactions hold enormous potential. However, the exploration of its catalytic activity in the degradation of water pollutants remains limited. Nevertheless, previous research has reported the catalytic activity of NP Au in the degradation of methyl orange (MO), a toxic azo dye commonly found in water. This study aims to investigate the behavior of nanoporous gold in MO solutions using UV-Vis absorption spectroscopy and high-performance liquid chromatography. The NP Au was prepared by chemical removal of silver atoms of an AuAg precursor alloy prepared by ball milling. Immersion tests were conducted on both pellets and powders of NP Au, followed by examination of the residual solutions. Additionally, X-ray photoelectron spectroscopy and electrochemical impedance measurements were employed to analyze NP Au after the tests. The findings reveal that the predominant and faster process involves the partially reversible adsorption of MO onto NP Au, while the catalytic degradation of the dye plays a secondary and slower role in this system.

The cobalt complex (I) with cyclopentadienyl and 2-aminothiophenolate ligands was investigated as a homogeneous catalyst for electrochemical CO₂ reduction. By comparing its behavior with an analogous complex with the phenylenediamine (II), the effect of sulfur atom as a substituent has been evaluated. As a result, a positive shift of the reduction potential and the reversibility of the corresponding redox process have been observed, also suggesting a higher stability of the compound with sulfur. Under anhydrous conditions, complex I showed a higher current enhancement in the presence of CO₂ (9.41) in comparison with II (4.12). Moreover, the presence of only one -NH group in I explained the difference in the observed increases on the catalytic activity toward CO₂ due to the presence of water, with current enhancements of 22.73 and 24.40 for I and II, respectively. DFT calculations confirmed the effect of sulfur on the lowering of the energy of the frontier orbitals of I, highlighted by electrochemical measurements. Furthermore, the condensed Fukui function f ⁻ values agreed very well with the current enhancement observed in the absence of water.

The present case study reports a shear rheological characterization in the temperature domain of inks and pastes loaded with conductive High Reactivity Carbonaceous Material (HRCM) consisting mainly of few-layers graphene sheets. The combined effect of filler concentration and applied shear rate is investigated in terms of the shear viscosity response as a function of testing temperature. The non-Newtonian features of shear flow ramps at constant temperature are reported to depend on both the HRCM load and the testing temperature. Moreover, temperature ramps at a constant shear rate reveal a different viscosity–temperature dependence from what is observed in shear flow ramps while maintaining the same filler concentration. An apparent departure from the well-known Vogel–Fulcher–Tamman relationship as a function of the applied shear rate is also reported.

A series of 6- and 6,8-halocoumarin derivatives have been investigated as potential antiproliferative compounds against a panel of tumor and normal cell lines. Cytotoxic effects were determined by the MTT method. To investigate the potential molecular mechanism involved in the cytotoxic effect, apoptosis assay, cell cycle analysis, reactive oxygen species (ROS), and reduced glutathione analysis were performed. Among the screened compounds, coumarins 6,8-dibromo-2-oxo-2H-chromene-3-carbonitrile 2h and 6,8-diiodo-2-oxo-2H-chromene-3-carbonitrile 2k exhibited the most antiproliferative effect in thyroid cancer-derived cells TPC-1. The apoptosis assay showed that both 2h and 2k induced apoptosis in TPC-1 thyroid cancer cells. According to these experiments, both coumarins induced a slight increase in TPC-1 cells in the G2/M phase and a decrease in the S phase. A significant increase in ROS levels was observed in TPC-1 treated with diiodocoumarin 2k, while the dibromocoumarin 2h induced a decrease in ROS in a dose and time-dependent manner.

Cobalt cyclopentadienyl phenylendiamine complexes are revealed to be efficient and selective electrocatalysts for CO ₂ reduction, resulting in a 31-fold catalytic current without the hydrogen evolution.