Search results for "Overpotential"
showing 10 items of 19 documents
Cathodic Corrosion of Metal Electrodes—How to Prevent It in Electroorganic Synthesis
2021
The critical aspects of the corrosion of metal electrodes in cathodic reductions are covered. We discuss the involved mechanisms including alloying with alkali metals, cathodic etching in aqueous and aprotic media, and formation of metal hydrides and organometallics. Successful approaches that have been implemented to suppress cathodic corrosion are reviewed. We present several examples from electroorganic synthesis where the clever use of alloys instead of soft neat heavy metals and the application of protective cationic additives have allowed to successfully exploit these materials as cathodes. Because of the high overpotential for the hydrogen evolution reaction, such cathodes can contri…
Cobalt Metal-Organic Framework Based on Layered Double Nanosheets for Enhanced Electrocatalytic Water Oxidation in Neutral Media
2020
A new cobalt metal-organic framework (2D-Co-MOF) based on well-defined layered double cores that are strongly connected by intermolecular bonds has been developed. Its 3D structure is held together by π-π stacking interactions between the labile pyridine ligands of the nanosheets. In aqueous solution, the axial pyridine ligands are exchanged by water molecules, producing a delamination of the material, where the individual double nanosheets preserve their structure. The original 3D layered structure can be restored by a solvothermal process with pyridine, so that the material shows a "memory effect"during the delamination-pillarization process. Electrochemical activation of a 2D-Co-MOF@Nafi…
Size-dependent electron transfer from atomically defined nanographenes to metal oxide nanoparticles.
2020
Atomically defined nanographenes (NGs) feature size-dependent energy gaps induced by, and tuneable through, quantum confinement. Their energy-tunability and robustness make NGs appealing candidates as active elements in sensitized geometries, where NGs functionalize a metal oxide (MO) film with large-area-to-volume ratio. Despite the prominent relevance of NG/MO interfaces for developing novel architectures for solar energy conversion, to date, little information is available regarding the fundamentals of electron transfer (ET) processes taking place from NG donors to MO acceptors. Here, we analyze the interplay between the size of atomically precise NGs and ET dynamics at NG/MO interfaces.…
A Universal Approach to Quantify Overpotential-Dependent Selectivity Trends for the Competing Oxygen Evolution and Peroxide Formation Reactions : A C…
2021
In this article, we study the competing oxygen evolution and hydrogen peroxide (H2O2) formation reactions for periodic models of graphene with different active-site concentrations by means of densi...
Bio-inspired Ni dinuclear complexes as heterogeneous catalysts for hydrogen evolution
2021
Abstract A major challenge in the sustainable production of hydrogen is lowering the electrochemical overpotential and the activation energy of the hydrogen evolution reaction. Some enzymes have two metallic Ni centers and catalyze this reaction with high activity. Taking inspiration from them, we have developed two novel dinuclear Ni(II) complexes, Ni-PATIO and Ni-PACO, with promise as molecular catalysts. Ni-PACO exhibits a square-planar geometry for both Ni(II) and two-fold rotational symmetry both in solid and solution states, whereas Ni-PATIO displays one square-planar Ni(II) center and one octahedral Ni(II) configuration, which confer it magnetic properties. We show that both complexe…
Direct involvement of acid centers of polyaniline in charge transfer on organic acceptor
1996
Abstract Electrochemical behavior of hydroquinone and 4F-hydroquinone has been studied on Pt/polyaniline (PANI) electrodes in 1 M H 2 SO 4 solution. Redox transformation of quinone/hydroquinone systems takes place on PANI practically without overpotential and, probably, the two-electron charge transfer processes are realized in such systems. Reaction currents depend on PANI quantities deposited on the Pt electrode and the molecular complex is formed. There exists a great electronic exchange between acid centers of PANI and quinone/hydroquinone molecules, resulting in electronic conjugation of this surface state (adsorbed molecule) with the polymer. Existence of such complexes was confirmed …
Superior Electrocatalytic Activity of MoS2-Graphene as Superlattice
2020
[EN] Evidence by selected area diffraction patterns shows the successful preparation of large area (cm x cm) MoS2/graphene heterojunctions in coincidence of the MoS2 and graphene hexagons (superlattice). The electrodes of MoS2/graphene in superlattice configuration show improved catalytic activity for H-2 and O-2 evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS2/graphene heterojunction with random stacking.
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…
A Comparative Study of Poly(Azure A) Film-Modified Disposable Electrodes for Electrocatalytic Oxidation of H₂O₂: Effect of Doping Anion.
2018
In the present paper, poly(azure A) (PAA) films were electrosynthetized in the presence of different doping anions on disposable screen-printed carbon electrodes (SPCEs). The anions used included inorganic monoatomic (chloride and fluoride), inorganic polyatomic (nitrate and sulfate) and organic polyatomic (dodecyl sulfate, DS) species. The coated electrodes thus obtained were characterized by electrochemical techniques and SEM. They showed improved electrocatalytic activities towards hydrogen peroxide oxidation compared to that of a bare SPCE. In particular, the insertion of DS anions inside PAA films provided a special sensitivity to the electrocatalysis of H2O2, which endowed these elect…
Electrodeposited nickel–zinc alloy nanostructured electrodes for alkaline electrolyzer
2022
Abstract Over the last decade, as a consequence of the global decarbonization process, the interest towards green hydrogen production has drastically increased. In particular a substantial research effort has focused on the efficient and affordable production of carbon-free hydrogen production processes. In this context, the development of more efficient electrolyzers with low-cost electrode/electrocatalyst materials can play a key role. This work, investigates the fabrication of electrodes of nickel-zinc alloys with nanowires morphology cathode for alkaline electrolyzers. Electrodes are obtained by the simple method of template electrosynthesis that is also inexpensive and easily scalable.…