57 research outputs found
Spontaneous doping of the basal plane of MoS2 single layers through oxygen substitution under ambient conditions
The chemical inertness of the defect-free basal plane confers environmental
stability to MoS2 single-layers, but it also limits their chemical versatility
and catalytic activity. The stability of the pristine MoS2 basal plane against
oxidation under ambient conditions is a widely accepted assumption in the
interpretation of various studies and applications. However, single-atom level
structural investigations reported here reveal that oxygen atoms spontaneously
incorporate into the basal plane of MoS2 single layers during ambient exposure.
Our scanning tunneling microscopy investigations reveal a slow oxygen
substitution reaction, upon which individual sulfur atoms are one by one
replaced by oxygen, giving rise to solid solution type 2D MoS2-xOx crystals. O
substitution sites present all over the basal plane act as single-atomic active
reaction centers, substantially increasing the catalytic activity of the entire
MoS2 basal plane for the electrochemical H2 evolution reaction.Comment: 6 pages, 5 figure
Laser Interactions for the Synthesis and In Situ Diagnostics of Nanomaterials
Laser interactions have traditionall been at thec center of nanomaterials science, providing highly nonequilibrium growth conditions to enable the syn- thesis of novel new nanoparticles, nanotubes, and nanowires with metastable phases. Simultaneously, lasers provide unique opportunities for the remote char- acterization of nanomaterial size, structure, and composition through tunable laser spectroscopy, scattering, and imaging. Pulsed lasers offer the opportunity, there- fore, to supply the required energy and excitation to both control and understand the growth processes of nanomaterials, providing valuable views of the typically nonequilibrium growth kinetics and intermediates involved. Here we illustrate the key challenges and progress in laser interactions for the synthesis and in situ diagnostics of nanomaterials through recent examples involving primarily carbon nanomaterials, including the pulsed growth of carbon nanotubes and graphene
Site-dependent reactivity of MoS2 nanoparticles in hydrodesulfurization of thiophene
N.S. and J.R.F. performed the experiments. N.S. analyzed the experimental data. S.R.
performed the theory. J.V.L. and M.M. planned and organized the studies. N.S. wrote the
first draft. J.V.L. wrote the final version. All authors contributed to the final version of the
manuscript.The catalytically active site for the removal of S from organosulfur compounds in catalytic
hydrodesulfurization has been attributed to a generic site at an S-vacancy on the edge of
MoS2 particles. However, steric constraints in adsorption and variations in S-coordination
means that not all S-vacancy sites should be considered equally active. Here, we use a
combination of atom-resolved scanning probe microscopy and density functional theory to
reveal how the generation of S-vacancies within MoS2 nanoparticles and the subsequent
adsorption of thiophene (C4H4S) depends strongly on the location on the edge of MoS2.
Thiophene adsorbs directly at open corner vacancy sites, however, we find that its adsorption
at S-vacancy sites away from the MoS2 particle corners leads to an activated and concerted
displacement of neighboring edge S. This mechanism allows the reactant to self-generate a
double CUS site that reduces steric effects in more constrained sites along the edge.The U.S. Department of Energy (DOEBasic Energy Sciences (BES)Office of Chemical SciencesCatalysis Science Program. DE‐FG02‐05ER15731National Energy Research Scientific Computing Center
(NERSC)Center for Nanoscale Materials (CNM)Argonne National
Laboratory (ANL)Department of Energy,
Office of Science, under contracts DE‐AC02‐06CH11357 and DE‐AC02‐05CH1123
Defect-Mediated Lithium Adsorption and Diffusion on Monolayer Molybdenum Disulfide
Monolayer Molybdenum Disulfide (MoS2) is a promising anode material for lithium ion batteries because of its high capacities. In this work, first principle calculations based on spin density functional theory were performed to investigate adsorption and diffusion of lithium on monolayer MoS2 with defects, such as single- and few-atom vacancies, antisite, and grain boundary. The values of adsorption energies on the monolayer MoS2 with the defects were increased compared to those on the pristine MoS2. The presence of defects causes that the Li is strongly bound to the monolayer MoS2 with adsorption energies in the range between 2.81 and 3.80 eV. The donation of Li 2s electron to the defects causes an enhancement of adsorption of Li on the monolayer MoS2. At the same time, the presence of defects does not apparently affect the diffusion of Li, and the energy barriers are in the range of 0.25–0.42 eV. The presence of the defects can enhance the energy storage capacity, suggesting that the monolayer MoS2 with defects is a suitable anode material for the Li-ion batteries
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