Molybdenum disulphide (MoS2) has been an attractive target for investigations in the fields of catalysis, sensing, energy storage, electronics, and optoelectronics. However, its potential application in the important area of environmental cleanup has not yet been effectively explored. With an intrinsically sulfur‐rich characteristic and unique 2D structure, MoS2 should be capable of mercury capture and removal. However, successful attempts to apply MoS2 to mercury removal are quite rare, presumably because the vast majority of sulfur atoms are located inside the bulk of MoS2 and are therefore inaccessible for mercury ions. Here, the first experimental evidence that MoS2 nanosheets with widened interlayer spacing are capable of mercury capture, with an extremely high mercury uptake capacity closely matching the theoretically predicted value (2506 mg g−1) and the largest distribution coefficient value (3.53 × 108 mL g−1) is provided. Remarkably, a single treatment of industrial wastewater (polyvinyl chloride industry) with this modified MoS2 could efficiently reduce the mercury concentration (126 p.p.b.) below U.S. Environmental Protection Agency limits for drinking water standards. The findings open up the possibility of expanding the applications of transition metal dichalcogenides in environmental remediation.
To alleviate the kinetic barriers associated with ORR (oxygen reduction reaction) and OER (oxygen evolution reaction) in electrochemical systems, efficient nonprecious electrocatalysts are urgently required. Here we report a facile soft-template mediated approach for fabrication of nanostructured cobalt-iron double sulfides that are covalently entrapped in nitrogen-doped mesoporous graphitic carbon (Co0.5Fe0.5S@N-MC). Notably, with a positive half-wave potential (0.808 V) and a high diffusion-limiting current density, the composite material delivers unprecedentedly striking ORR electrocatalytic activity among recently reported nonprecious late transition metal chalcogenide materials in alkaline medium. Various characterization techniques, including X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction, are conducted to elucidate the correlation between structural features and catalytic activities of the composite. Moderate substitution and well-dispersion of iron in bimetallic sulfide composites are believed to have positive effect on the adsorption and activation of oxygen-containing species, thus leading to conspicuous ORR and OER catalytic enhancement compared to their monometallic counterparts. Besides, the covalent bridge between active sulfide particles and mesoporous carbon shells provides facile pathways for electron and mass transport. Beneficially, the intimate coupling interaction renders prolonged electrocatalytic performances to the composite. Our results may possibly lend a new impetus to the rational design of bi- or multimetallic sulfides encapsulated in porous carbon with improved performance for electrocatalysis and energy storage applications.
Flexible
supercapacitors with considerable energy storage performance
from green/sustainable materials have attracted significant attention
in many fields, such as portable and wearable electronics. In this
work, flexible cellulose nanofibers/reduced graphene oxide/polypyrrole
(CNFs/rGO/PPy) aerogel electrodes with well-defined three-dimensional
porous structures are prepared using citric acid-Fe3+ (CA-Fe3+) complexes as oxidant precursors to command the deposition
of PPy. The in situ gradual release of Fe3+ leads to the
formation of thin and uniform polypyrrole in the composites. A flexible
all-solid-state supercapacitor is then prepared by the CNFs/rGO/PPy
aerogel film electrode and poly(vinyl alcohol) (PVA)/H2SO4 gel electrolyte and separator. Due to the porous structure,
high electrical conductivity, and remarkable wettability of the electrodes,
the assembled supercapacitors show excellent electrochemical properties
with maximum areal capacitance of 720 mF cm–2 (405
F g–1 for single electrode) at 0.25 mA cm–2 and good cycle stability (95% retention after 2000 cycles). The
device with maximum energy density of 60.4 μW h cm–2 also exhibits nearly constant capacitance under different bending
conditions, suggesting their great potential for applications in flexible
electronics.
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