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The cathodic reduction of pressurized CO2 (PrCO2CR) at suitable cathodes can allow to produce various chemicals, such as formic acid/formate (FA) and carbon monoxide or synthesis gas, with high faradic efficiencies (FEs) and productivities. Here, we have performed the conversion of CO2 in an undivided pressurized electrochemical reactor using silver cathode in order to determine the optimal values of CO2 pressure and current density. It was found that the plot FE vs. pressure resulted in a curve with a maximum. Similarly, an optimal value of current density can be selected for the PrCO2CR. The competition between the production of carbon monoxide and formic acid/formate is strongly affected by both the pressure and the current density. Eventually the effect of pressure and current density on the economic figures of the process was evaluated. [ABSTRACT FROM AUTHOR]

Microalgae are photosynthetic microorganisms which may be employed in several fields. Amongst them, an emerging but promising sector of application is their usage for the remediation of wastewaters. They result particularly effective in treating municipal wastewaters, often resulting in nitrate concentrations exceeding the requirements for discharging treated wastewater into the sea. Furthermore, another advantage of using microalgae in civil wastewater treatment is the cooperation with heterotrophic bacteria which may naturally occur in the water or be introduced through sewage sludge in wastewater treatment plants (WTPs). Microalgae, in fact, produce oxygen which may be used by these bacteria reducing the overall operational costs of the WTP. The assessment of nitrogen compound concentrations in wastewater involves various techniques, with ionic chromatography (IC) and spectrometric methods being commonly used in laboratory settings. However, these methods have drawbacks such as the need for skilled personnel, time-consuming processes, and impracticality for in situ and real-time analysis. To address these issues, electrochemical sensors present a viable alternative. These sensors require portable instruments with low power requirements and can be miniaturized using nanotechnology. Electrochemical sensors operate by reducing/oxidizing the target analyte on the working electrode surface. The choice of electrode material is crucial for sensor sensitivity, and copper is found to exhibit excellent electrocatalytic properties for reducing nitrate ions in acidic media. In this study, a cost-effective electrochemical sensor made of copper was developed for quantifying nitrate in wastewater. The entire electrochemical cell was constructed from a common substrate used in Printed Circuit Boards (PCB). The whole fabrication procedure was optimized in order to obtain a reproducible fabrication procedure. The reference and counter electrodes were modified with graphite and Ag/AgCl paste, respectively. The results demonstrated that the sensor can effectively quantify nitrate ions in wastewater. Moreover, it can be employed during microalgal treatment to assess the in vivo reduction of nitrate, offering a practical and efficient solution for real-time monitoring of nitrogen compounds in wastewater treatment processes. [ABSTRACT FROM AUTHOR]

In recent years, the interest towards green hydrogen has drastically increased due to the global decarbonization process. Electrochemical water splitting is considered an attractive solution to convert and store the surplus energy from renewable energy sources. However, hydrogen production by water electrolysis is not economically sustainable. To reduce the cost of produced hydrogen, it is necessary to switch from noble-metal catalyst (Pt, Pd…) to cheap alternatives with a lower per unit energy cost but at the same time able to guarantee a high electrocatalytic activity for both oxygen and hydrogen evolution reactions. Among transition metals, nickel was selected as active material for its low cost and high chemical stability in alkaline media. Currently, the most investigated transition metal catalyst includes alloy of nickel with sulfide, phosphide, and nitride. In this work, a ternary alloy of Nickel-Iron-Phosphorus with nanowires morphology was investigated and compared to the binary alloy of Nickel-Iron. Ni-Fe-P NWs electrodes were obtained by potential-controlled pulse electrochemical deposition using polycarbonate membrane as template. Electrodes morphology and structure were studied by scanning electrode microscopy (SEM), energy diffraction spectroscopy (EDS) and X-ray diffraction (XRD). Electrodes were tested both as cathodes as anodes by Quasi Steady State Polarization (QSSP) and Galvanostatic Test. All the tests were performed in 30% w/w KOH aqueous solution at room temperature. Preliminary results showed better performance of the ternary alloy compared to the binary one. [ABSTRACT FROM AUTHOR]

In this work, an innovative and cheap electrochemical sensor for hydrogen peroxide quantification in exhaled breath was developed. H2O2 is the most used biomarker among the Reactive Oxygen Species (ROS) for monitoring the level of oxidative stress in the respiratory system. This is due to its stability and ability to cross biological membranes and also because it is detectable in extracellular space. The electrochemical sensor was obtained using the silver layer of wasted compact discs (CDs). All three electrodes, working (WE), counter (CE), and pseudo-reference electrode (RE), were fabricated using a laser cutter. The working electrode was used directly, while an Ag/AgCl paste and a graphite paste were applied respectively on the RE and the CE. In addition, a chitosan layer was deposited by Electro-Phoretic Deposition (EPD) on the surface of the sensor. This biopolymer improves the wettability of the sensor in presence of a humid atmosphere such as that given by exhaled air. The sensor was tested in both liquid and nebulized solutions containing different concentrations of hydrogen peroxide. The detection of H2O2 was evaluated using Linear Sweep Voltammetry (LSV) as electrochemical technique. The results show that the peak current increases linearly with hydrogen peroxide concentration from 100 to 500 μM with a sensitivity of 0.068 µA µM−1 cm−2 and 0.108 µA µM−1 cm−2, a Limit Of Detection (LOD) of 60 μM and 30 μM respectively for liquid and nebulized solutions. Therefore, the use of the electrochemical sensor can allow the monitoring of hydrogen peroxide in real time with good results. [ABSTRACT FROM AUTHOR]