Search results for "Hydrogen evolution"

Microwave-assisted chemical modification of g-C3N4 for photoinduced processes: organic degradation, hydrogen production and selective oxidation of al…

2023

g-C3N4 powders were treated by means of the microwave technique in three different aqueous and organic media (HNO3, NaOH and N,N-dimethylformamide). All powders were analyzed by XRD reveling that g-C3N4 maintains its structure. The morphology of the samples was analyzed with scanning electron microscopy, where the micrographs reveals that the modifcation occurs on the surface of the g-C3N4. The photocatalytic activity of the samples was evaluated in the degradation of ciprofoxacin, hydrogen production and for the selective partial oxidation of 4-methoxybenzylalcohol (4-MBA) to its aldehyde. The sample treated with HNO3 (C3N4-HNO3) shows the best photocatalytic performance in the degradation…

A mathematical description accounting for the superfluous hydrogen evolution and the inductive behaviour observed during electrochemical measurements…

2018

When electrochemical techniques are used to probe the surface of corroding magnesium with the aim of obtaining quantitative information on the corrosion process, two peculiarities are generally observed: i) with anodic polarization, the rate of hydrogen evolution increases instead of decreasing and ii) during electrochemical impedance spectroscopy measurements, an inductive contribution is often observed at the low-frequency end of the spectra. The presence of these two phenomena clearly has an impact on the methodology that should be applied to correctly estimate corrosion rates from electrochemical data. The aim of this work is to provide a general mathematical description of the corrodin…

Electrochemical Characterization of Coinage Techniques the 17(th) Century: The maravedis Case

2017

[EN] The voltammetry of immobilized particles (VIMP) methodology was applied to the discrimination of Spanish maravedis produced in 10 different mints between 1661 and 1664 using characteristic signatures for the reduction of cuprite and tenorite in the patina of the coins and catalytic effects on the hydrogen evolution reaction (HER). The variation of the apparent tenorite/cuprite ratio with depth was fitted to potential laws differing from one mint to another for A Coruna, Burgos, Cordoba, Cuenca, Granada, Madrid, Trujillo, Segovia, Sevilla and Valladolid coins. Electrochemical data permitted to detect the changes in the composition (with lowering of the silver content) and manufacturing …

Nanostructured electrodes for hydrogen production in alkaline electrolyzer

2018

Abstract Ever-widespread employment of renewable energy sources, such as wind and sun, request the simultaneous use of effective energy storage systems owing to the intermittent and unpredictable energy generation by these sources. The most reliable storage systems currently under investigation are batteries and electrochemical cells for hydrogen production from water splitting. Both systems store chemical energy which can be converted on demand. The low power density is the weakness of the batteries while the high production cost limits currently the wide use of hydrogen from electrochemical water splitting. In this work, attention was focused on the use of nanostructured Ni as a cathode f…

Droplet cell investigation of intergranular corrosion on AA2024

2017

An original method combining a droplet cell with direct optical interrogation of the reverse side of a 50μm thick foil AA2024 has been tested to evaluate the possible analysis of the current during intergranular corrosion tests. The foil microstructure and the selected orientation were suitable for recording the current generated during the propagation in volume of a well-defined grain boundary trace. Even if it is impossible to reach a charge and mass balance from these preliminary attempts, it was demonstrated that it is possible, despite hydrogen evolution, to record a current transient resulting from the full penetration of an intergranular path. Keywords: Intergranular corrosion, Alumi…

The Hydrogen‐Storage Challenge: Nanoparticles for Metal‐Catalyzed Ammonia Borane Dehydrogenation

2021

International audience; Dihydrogen is one of the sustainable energy vectors envisioned for the future. However, the rapidly reversible and secure storage of large quantities of hydrogen is still a technological and scientific challenge. In this context, this review proposes a recent state-of-the-art on H 2 production capacities from the dehydrogenation reaction of ammonia borane (and selected related amine-boranes) as a safer solid-source of H 2 by hydrolysis (or solvolysis), according to the different developed nanoparticle-based catalysts. The review groups the results according to the transition metals constituting the catalyst according a special view to current cost/availability consid…

2018

Abstract When electrochemical techniques are used to probe the surface of corroding magnesium with the aim of obtaining quantitative information on the corrosion process, two peculiarities are generally observed: i) with anodic polarization, the rate of hydrogen evolution increases instead of decreasing and ii) during electrochemical impedance spectroscopy measurements, an inductive contribution is often observed at the low-frequency end of the spectra. The presence of these two phenomena clearly has an impact on the methodology that should be applied to correctly estimate corrosion rates from electrochemical data. The aim of this work is to provide a general mathematical description of the…

Two Novel Polyoxometalate-Encapsulated Metal–Organic Nanotube Frameworks as Stable and Highly Efficient Electrocatalysts for Hydrogen Evolution React…

2018

Two novel polyoxometalate (POM)-encapsulated metal–organic nanotube (MONT) framework crystalline materials with unprecedented copper-mixed ligands, HUST-200 and HUST-201, have been successfully synthesized by an effective synthesis strategy. The encapsulation not only provides a shield to increase the chemical stability, but also does not affect its catalytic activity, and, therefore, the crystalline materials are very active for HER (H+ can diffuse easily through the pores of the MONTs). Remarkably, HUST-200 displays a low overpotential of 131 mV (catalytic current density is equal to 10 mA·cm–2). This work thus offers a new way for devising HER electrocatalysts with low cost using POM-enc…

Ni alloy nanowires as high efficiency electrode materialsnfor alkaline electrolysers

2020

Hydrogen production by water electrolysis (WE) is a very promising technology because it is a pollution-free process especially if renewable sources are employed to energy supply. Nowadays, the cost of hydrogen production by WE is higher than other available technologies, which makes WE not competitive. Many efforts have been made to improve WE performance, through the use of electrodes made of transition metal alloys as cathode and compound of metal oxide as anode [1]. In the field of water-alkaline electrolyzer, the development of cheap nanoporous based nickel electrodes with high electrocatalytic features is one of the potential approaches to increase the WE performance [2]. A facile met…

Bimetallic Intersection in PdFe@FeO x ‐C Nanomaterial for Enhanced Water Splitting Electrocatalysis

2022

Supported Fe-doped Pd-nanoparticles (NPs) are prepared via soft transformation of a PdFe-metal oraganic framework (MOF). The thus synthesized bimetallic PdFe-NPs are supported on FeO@C layers, which are essential for developing well-defined and distributed small NPs, 2.3 nm with 35% metal loading. They are used as bifunctional nanocatalysts for the electrocatalytic water splitting process. They display superior mass activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER), both in alkaline and acid media, compared with those obtained for benchmarking platinum HER catalyst, and ruthenium, and iridium oxide OER catalysts. PdFe-NPs also exhibit outstanding sta…