Bipolar Electrochemistry Exfoliation of Layered Metal Chalcogenides Sb S and Bi S and their Hydrogen Evolution Applications.

Efficient exfoliation and downsizing of Sb S and Bi S layered compounds by using scalable bipolar electrochemistry on their suspensions in aqueous media are here demonstrated. The resulting samples were characterized in detail by transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy; their electrochemistry toward hydrogen evolution was also investigated. Hydrogen evolution ability of exfoliated Sb S and Bi S was investigated and compared to the bulk counterparts.

Two-Dimensional Materials on the Rocks: Positive and Negative Role of Dopants and Impurities in Electrochemistry.

Two-dimensional (2D) materials, such as graphene and transition-metal chalcogenides, were shown in many works as very potent catalysts for industrially important electrochemical reactions, such as oxygen reduction, hydrogen and oxygen evolution, and carbon dioxide reduction. We critically discuss here the development in the field, showing that not only dopants but also impurities can have dramatic effects on catalysis. Note here that the difference between dopant and impurity is merely semantic-dopant is an impurity deliberately added to the material.

Composition-Graded MoWS Hybrids with Tailored Catalytic Activity by Bipolar Electrochemistry.

Among transition metal dichalcogenide (TMD)-based composites, TMD/graphene-related material and bichalcogen TMD composites have been widely studied for application toward energy production via the hydrogen evolution reaction (HER). However, scarcely any literature explored the possibility of bimetallic TMD hybrids as HER electrocatalysts. The use of harmful chemicals and harsh preparation conditions in conventional syntheses also detracts from the objective of sustainable energy production.

Electrosynthesis of Bifunctional WS /Reduced Graphene Oxide Hybrid for Hydrogen Evolution Reaction and Oxygen Reduction Reaction Electrocatalysis.

A multitude of research into the application of transition-metal dichalcogenides as earth-abundant hydrogen evolution reaction (HER) electrocatalysts has been conducted. However, current synthetic methods generally deploy environmentally harmful chemicals and energy-consuming reaction conditions, despite the primary intent to attain renewable energy production. Here, the desirable properties of tungsten sulfide and reduced graphene oxide (rGO) have been combined and hybrid materials have been fabricated through simultaneous electrochemical reduction and synthesis, as a versatile and environmentally benign alternative to conventional fabrication techniques.

A study of the effect of sonication time on the catalytic performance of layered WS from various sources.

WS is a transition metal dichalcogenide (TMD) with many potential applications from catalysis to sensing, and is of interest both in its bulk and monolayer forms. There is discrepancy in the literature on the reported electrocatalytic effect of layered WS. In this study, we examine two issues: the influence of the WS source and the effect of a common agitation technique via ultrasonication on the observed electrocatalysis.

The Origin of MoS Significantly Influences Its Performance for the Hydrogen Evolution Reaction due to Differences in Phase Purity.

Molybdenum disulfide (MoS ) is at the forefront of materials research. It shows great promise for electrochemical applications, especially for hydrogen evolution reaction (HER) catalysis. There is a significant discrepancy in the literature on the reported catalytic activity for HER catalysis on MoS .

Bottom-up Electrosynthesis of Highly Active Tungsten Sulfide (WS3-x) Films for Hydrogen Evolution.

Transition metal dichalcogenides have been extensively studied as promising earth-abundant electrocatalysts for hydrogen evolution reaction (HER). However, despite the intention to achieve sustainable energy generation, conventional syntheses typically use environmentally damaging reagents and energy-demanding preparation conditions. Hence, we present electrochemical synthesis as a green and versatile alternative to traditional methods.

Electrochemistry of layered GaSe and GeS: applications to ORR, OER and HER.

Though many studies examined the properties of the class of IIIA-VIA and IVA-VIA layered materials, few have delved into the electrochemical aspect of such materials. In light of the burgeoning interest in layered structures towards various electrocatalytic applications, we endeavored to study the inherent electrochemical properties of representative layered materials of this class, GaSe and GeS, and their impact towards electrochemical sensing of redox probes as well as catalysis of oxygen reduction, oxygen evolution and hydrogen evolution reactions. In contrast to the typical sandwich structure of MoS2 layered materials, GeS is isoelectronic to black phosphorus with the same structure; GaSe is a layered material consisting of GaSe sheets bonded in the sequence Se-Ga-Ga-Se.

Impact Electrochemistry of Layered Transition Metal Dichalcogenides.

Layered transition metal dichalcogenides (TMDs) exhibit paramount importance in the electrocatalysis of the hydrogen evolution reaction. It is crucial to determine the size of the electrocatalytic particles as well as to establish their electrocatalytic activity, which occurs at the edges of these particles. Here, we show that individual TMD (MoS2, MoSe2, WS2, or WSe2; in general MX2) nanoparticles impacting an electrode surface provide well-defined current "spikes" in both the cathodic and anodic regions.

Sulfur poisoning of emergent and current electrocatalysts: vulnerability of MoS2, and direct correlation to Pt hydrogen evolution reaction kinetics.

The recent surge in interest in the utilisation of transition metal dichalcogenides for the hydrogen evolution reaction (HER), as well as the long-standing problem of sulfur poisoning suffered by the established Pt HER electrocatalyst, motivated us to examine the impacts of sulfur poisoning on both emergent and current electrocatalysts. Through a comparative study between MoS2 and Pt/C on the effects of sulfur poisoning, we demonstrate that MoS2 is not invulnerable to poisoning. Additionally, using X-ray photoelectron spectroscopy, correlations have also been established between the atomic percentages of Pt-S bonds and normalised HER parameters e.

Pristine Basal- and Edge-Plane-Oriented Molybdenite MoS2 Exhibiting Highly Anisotropic Properties.

The layered structure of molybdenum disulfide (MoS2 ) is structurally similar to that of graphite, with individual sheets strongly covalently bonded within but held together through weak van der Waals interactions. This results in two distinct surfaces of MoS2 : basal and edge planes. The edge plane was theoretically predicted to be more electroactive than the basal plane, but evidence from direct experimental comparison is elusive.

Towards electrochemical purification of chemically reduced graphene oxide from redox accessible impurities.

The electrochemical properties of graphene are highly sensitive to residual metallic impurities that persist despite various purification efforts. To accurately evaluate the electrochemical performance of graphene, highly purified materials free of metallic impurities are required. In this study, the partial purification of chemically reduced graphene oxides prepared via Hummers (CRGO-HU) and Staudenmaier (CRGO-ST) oxidation methods was performed through cyclic voltammetric (CV) scans executed in nitric acid, followed by CV measurements of cumene hydroperoxide (CHP).

Boron-doped graphene and boron-doped diamond electrodes: detection of biomarkers and resistance to fouling.

Doped carbon materials are of high interest as doping can change their properties. Here we wish to contrast the electrochemical behaviour of two carbon allotropes - sp(3) hybridized carbon as diamond and sp(2) hybridized carbon as graphene - doped by boron. We show that even though both materials exhibit similar heterogeneous electron transfer towards ferro/ferricyanide, there are dramatic differences towards the oxidation of biomolecules, such as ascorbic acid, uric acid, dopamine and β-nicotinamide adenine dinucleotide (NADH).

Graphenes prepared from multi-walled carbon nanotubes and stacked graphene nanofibers for detection of 2,4,6-trinitrotoluene (TNT) in seawater.

The study on explosive materials is paramount due to the potential hazards to national security and health. When disposed of, explosives can cause seawater pollution. The detection of 2,4,6-trinitrotoluene (TNT) in seawater has been examined on two different forms of graphene, mainly graphene prepared from the unzipping of multi-walled carbon nanotubes (MWCNTs) and from the exfoliation of stacked graphene nanofibers (SGNFs).