Enhancing
the intrinsic activity of a benchmarked electrocatalyst
such as platinum (Pt) is highly intriguing from fundamental as well
as applied perspectives. In this work, hydrogen evolution reaction
(HER) activity of Pt electrodes, benchmarked HER catalysts, modified
with ultrathin sheets of hexagonal boron nitride (h-BN) is studied
in acidic medium (Pt/h-BN), and augmented HER performance, in terms
of the overpotential at a 10 mA cm–2 current density
(10 mV lower than that of Pt nanoparticles) and a lower Tafel slope
(29 ± 1 mV/decade), of the Pt/h-BN system is demonstrated. The
effects of h-BN surface modification of bulk Pt as well as Pt nanoparticles
are studied, and the origin of such an enhanced HER activity is probed
using density functional theory-based calculations. The HER charge
transfer resistance of h-BN-modified Pt is found to be drastically
reduced, and this enhances the charge transfer kinetics of the Pt/h-BN
system because of the synergistic interaction between h-BN and Pt.
An enormous reduction in the hydrogen adsorption energy on h-BN monolayers
is also found when they are placed over the Pt electrode [−2.51
eV (h-BN) to −0.25 eV (h-BN over Pt)]. Corrosion preventive
atomic layers such as h-BN-protected Pt electrodes that perform better
than Pt electrodes do open possibilities of benchmarked catalysts
by simple modification of a surface via atomic layers.
Controlled
assembly of mesoscopic structures can bring interesting
phenomena because of their interfaces. Here, carbon nanotubes (CNTs)
are cross-coupled via a C–C bonding through Suzuki reaction
resulting in three-dimensional (3D) CNT sponges, and these 3D CNTs
are studied for their efficacy toward the electrocatalytic hydrogen
evolution reaction (HER) in acidic mediumone of the promising
methods for the production of a renewable energy source, hydrogen.
Both single and multiwall CNTs (SWCNTs and MWCNTs) are studied for
the development of 3DSWCNTs and 3DMWCNTs, and these 3D CNTs are found
to be HER active with small reaction onset potentials and low charge-transfer
resistances unlike their uncoupled counterparts. First-principle density
functional calculations show that the combination of electron acceptor
and donor bonded to the CNT network can provide a unique band structure
modulation in the system facilitating the HER reaction. This study
can provide possibilities for band engineering of CNTs via functionalization
and cross-coupling reactions.
Hotspot
engineering has the potential to transform the field of
surface-enhanced Raman spectroscopy (SERS) by enabling ultrasensitive
and reproducible detection of analytes. However, the ability to controllably
generate SERS hotspots, with desired location and geometry, over large-area
substrates, has remained elusive. In this study, we sculpt artificial
edges in monolayer molybdenum disulfide (MoS2) by low-power
focused laser-cutting. We find that when gold nanoparticles (AuNPs)
are deposited on MoS2 by drop-casting, the AuNPs tend to
accumulate predominantly along the artificial edges. First-principles
density functional theory (DFT) calculations indicate strong binding
of AuNPs with the artificial edges due to dangling bonds that are
ubiquitous on the unpassivated (laser-cut) edges. The dense accumulation
of AuNPs along the artificial edges intensifies plasmonic effects
in these regions, creating hotspots exclusively along the artificial
edges. DFT further indicates that adsorption of AuNPs along the artificial
edges prompts a transition from semiconducting to metallic behavior,
which can further intensify the plasmonic effect along the artificial
edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated)
edges of the MoS2 sheet. To demonstrate the practical utility
of this concept, we use our substrate to detect Rhodamine B (RhB)
with a large SERS enhancement (∼104) at the hotspots
for RhB concentrations as low as ∼10–10 M.
The single-step laser-etching process reported here can be used to
controllably generate arrays of SERS hotspots. As such, this concept
offers several advantages over previously reported SERS substrates
that rely on electrochemical deposition, e-beam lithography, nanoimprinting,
or photolithography. Whereas we have focused our study on MoS2, this concept could, in principle, be extended to a variety
of 2D material platforms.
Sunlight-responsive anatase N-doped TiO2 thin films undergoing reversible and switchable hydrophobic to superhydrophilic transition were synthesized by ultrasonic spray pyrolysis in a single step. Film thickness, roughness, surface morphology, crystal structure, composition, band gap, and wetting properties were studied using surface profilometry, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis spectroscopy, and water contact angle measurements, respectively. Surface X-ray photoelectron spectroscopy before and after sunlight irradiation revealed the major physicochemical process responsible for the hydrophobic → hydrophilic transition as surface hydroxylation and that responsible for hydrophilic → superhydrophilic transition as destruction of surface adsorbed organic species. The kinetic rates of the hydrophobic → superhydrophilic transition under sunlight and superhydrophilic → hydrophobic transition when kept under dark are found to be 0.215 min(-1) and 2.03 × 10(-4) min(-1), respectively.
2This paper reports detailed EXAFS analysis of spray pyrolysis synthesized TiO 2 thin films to, 3 locate position of nitrogen in N-doped phase pure(anatase)TiO 2 , evaluate Ti-O bond distances 4 and the co-ordination number of Ti. The thin films were synthesized at three different substrate 5 temperatures viz. 400, 450 and 500 o C leading to concomitant occurrence of varying nitrogen 6 concentration (N/Ti) of 0.282, 0.237, 0.24 respectively. The co-ordination number extracted 7 from the EXAFS fitting revealed that films synthesized at 450 o C are stoichiometric, whereas 8 those synthesized at 400 and 500 o C are sub-stoichiometric. The intensity of near edge peaks 9 in XAS was employed to delineate the contribution from both symmetry of TiO 6 polyhedra 10 and particle size. The axial and equatorial Ti-O bond distances, corresponding to the different nitrogen concentrations, extracted from the EXAFS fitting, showed good agreement with those 12 calculated from DFT calculations quoted in literature. An increase in the axial and equatorial 13 bond distances with respect to pristine TiO 2 is observed and is attributed to the dominant effect 14 of nitrogen occupancy in the interstitial position.15
The present study deals with the water quality of Talcher Area. Sample was collected from Ghats of river Brahmani, tube well and tap water of different colonies in Monsoon and in Post Monsoon. The collected sample was analysed in P.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.