We report a reinterpretation of the reduction of 4-nitrophenol catalyzed by silver nanoparticles. Mass spectrometry and ultraviolet−visible light spectroscopy measurements support the existence of 4-nitrosophenol as a stable reaction intermediate. We propose that dissolved oxygen is consumed, both by oxidizing 4nitrosophenol (an intermediate) and reoxidizing the reduced catalyst surface, resulting in the commonly observed "induction period" in the reaction kinetics. Upon complete consumption of dissolved oxygen, subsequent reduction to 4-aminophenol can occur. A complete kinetic analysis including modeling is presented, conceptually fitting data from recent reports in the literature, as well as fitting data from our own experiments.
Transition
metal dichalcogenides (TMDs) of molybdenum and tungsten
are layered van der Waals materials that exhibit a rich array of polytypes.
The different possible arrangements of the constituents of the “two-dimensional”
MX2 sheets (where M = group 4–10 elements, X = chalcogen)
give rise to a host of interesting and tunable phenomena. Molybdenite,
or molybdenum disulfide (MoS2) in its most abundant and
thermodynamically stable form, 2H-MoS2, is perhaps the
most widely used TMD, though the potential applications of its metastable
polytypes have been recognized only recently. From among the polytypes,
the 3R-MoS2 (rhombohedral) phase has attracted the most
interest because of its thermodynamic stability, ABC stacking (as
opposed to the AA′ of the more common 2H-MoS2),
and lack of inversion symmetry. These properties make it an excellent
candidate for photonics, optoelectronics, and catalysis. Because the
literature on this material is rapidly expanding, this review seeks
to summarize the history, known and predicted characteristics, syntheses,
and applications, as well as common misconceptions of, and surrounding,
3R-MoS2. Although the review is chemically focused, it
includes suggested reading to cover a broader scope.
The unique anisotropy, polytypism, and abundance of molybdenum disulfide make it a singularly versatile material for a range of catalytic, electrochemical, and tribological applications. By employing a hydrothermal synthesis, a...
Reactive methanol removal either by adsorption or by azeotropic distillation promotes complete conversion of different alcohols to the corresponding carbonates.
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