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(a) CV curves of the MoS2 powder electrodes; measured in 0.5 M H2SO4 at a scan rate of 10 mV/s; the data were iR-corrected according to the procedure described in the experimental section; for Cdl corrected curves see Figure S2; (b) dependence of the current density at −0.3 V vs. RHE on particle size, the data were taken from Figure 4 (a).
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Molybdenum sulfide is of interest as a noble metal-free catalyst for the hydrogen evolution reaction (HER). In crystallized form, it shows a typical stacking of planar S–Mo–S layers whereas the catalytically active centers are situated on the edges of these entities characterized by non-saturated bonds of the molybdenum atoms. In this study, 2H-MoS...
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Citations
... The peaks broadening and shifting attributed to many factors viz. number of MoS 2 layers, elemental composition, formation of defective carbon, extension in van-der-walls interaction among layers and strain in layers [38]. The small peak around 281.6 cm − 1 with small intensity corresponds to E 1g, is due to MoS 2 curvature around MWCNTs [34]. ...
Nitrophenols are industrially versatile yet environmentally detrimental compounds. Herein, we have synthesised molybdenum sulphide based dichalcogenide supported multiwalled carbon nanotubes i.e. MoS 2 @MWCNTs electrocatalyst by simple wet chemical method for PA determination. The successful decoration of MoS 2 over MWCNTs were confirmed by various characterizations techniques including scanning electron microscopy (SEM) shows MoS 2 layers grown on MWCNTs and having average size is-80 nm. Energy dispersive X-ray analysis (EDAX) reveals elements are homogenously distributed in nanocomposite. High resolution-transmission electron microscopy (HR-TEM) shows increase in average diameter after decoration of MoS 2 over MWCNTs from 30 nm to 70 nm. The Fourier transform infrared (FT-IR) analysis suggests the presence of Mo-S stretching frequency at 605 cm − 1 in addition to hydroxyl, carbonyl, CC , CO stretching frequencies are also observed. In Raman spectrum from apart D and G bands, the characteristic intense bands E 2g 1 and A 1g of MoS 2 were pointed towards presence of molybdenum and sulphur. The X-ray diffraction (XRD) confirms synthesised electrocatalyst is in hexagonal crystal structure with P63/mmc space group. The X-ray photoelectron spectroscopy (XPS) reveals that for Mo 3d is found to be two characteristics peaks at 231.2 eV and 233.2 eV corresponds to Mo 4+ 3d 3/2 and 3d 5/2 respectively. The peak at 229 eV corresponds to S 2s. Whereas, the signal appears at 162.7 eV, 165 eV, 169 eV and 170 eV shows sulphur is in 2S 3/2 and 2S5 /2 states. Electrochemical performance was examined by cyclic voltammetry (CV) tests. The Electrocatalyst is highly selective, having appreciable anti-interference property, lower limit of detection (LoD), i.e., 0.5 μM with wide linear range. The low R ct and high k⁰ pointed that MoS 2 @MWCNTs performed better towards electrochemical detection of PA.
... The average crystallite size of CuCo 2 S 4 is ~17.6 nm. The low crystallite size of CuCo 2 S 4 narrates a highly active surface area, which causes improvement in water electrolysis [17,43]. The chemical bonding and phase characteristics of CuCo 2 S 4 nanosheets were further chronicled by Raman spectroscopy, as shown in Fig. 3(b). ...
One potential method to lower the cost of electrocatalytic green hydrogen production is to use metal sulfide-based electrocatalysts in hybrid water electrolysis. This work uses a one-step hydrothermal synthesis to create copper cobalt sulphide (CuCo 2 S 4) nanosheets for hybrid water splitting. Significant water-splitting activity was achieved using urea and organic dye (methylene blue) as supporting electrolytes to avoid delayed OER kinetics. For the KOH + urea and KOH + organic dye electrolytes, the working electrode displays an overpotential of 1.37 V against RHE and 1.30 V vs RHE, respectively, to yield a current density of 10 mA/cm 2. The CuCo 2 S 4 working electrode exhibits an overpotential of 212 mV versus RHE and 158 mV vs RHE at 10 mA/cm 2 current density while monitoring hydrogen evolution reaction (HER) activity. For the KOH + organic dye electrolyte, the electrode exhibits exceptionally efficient electrocatalytic water splitting, with an overpotential of 1.50 V at a current density of 10 mA/cm 2. At high current densities, the CuCo 2 S 4 working electrode shows exceptional stability at industry standards throughout a broad pH range of basic, acidic, neutral, and saline environments. The use of several supporting electrolytes demonstrates an overall water splitting that is energy-efficient. Wastewater treatment can be accomplished through a circular economy strategy by merging the goals of environmental remediation (dye degradation) and renewable energy production (hydrogen evolution). This approach promotes sustainable growth, reduces waste, and encourages resource recovery. According to the internationally endorsed Sustainable Development Goals (SDGs), treating wastewater has the potential to help achieve 11 of the 17 SDGs.
... More importantly, engineering such defects requires an elaborate setup and produces limited amounts of the catalyst that significantly hinders its wide-scale utilization. Previous reports demonstrated the feasibility of constructing composite structures of MoS 2 sheets and multi-walled carbon nanotubes (MWCNTs), producing wrapped nanotubes by partially bended stacks or hexagonal cylinders of MoS 2 layers, 20 or orthogonal attachment of MoS 2 sheets to the nanotube support. 21−23 Alternative to crystalline MoS 2 catalysts, amorphous MoS x demonstrated high catalytic activity in promoting the HER, yet it is challenging to engineer such amorphous phases with desirable impact on activity. ...
Amorphous, mixed-valency, molybdenum sulfide (MoS x) with a proposed formula, [Mo (IV) 4 Mo (V) 2 (S 2 2−) 3 (S 2−) 5 ](SO 4) 5 , was grown through a one-pot, solvothermal synthesis on multi-walled carbon nanotubes (MWCNTs) in a gram-scale setup. Optimizing the loading of the active catalyst relative to the conductive support resulted in optimized catalytic performance in hydrogen evolution reaction, reaching down to one of the lowest reported overpotentials, η 10 = 140 mV and η 100 = 198 mV with a Tafel slope of 62 mV/dec, for the 6.5 wt % of MoS x @MWCNTs. Engineering this amorphous MoS x catalyst was made possible through control of the oxidation state of Mo to avoid the fully reduced MoS 2 phases. We also demonstrate that engineering defects in the MoS x catalyst does not require sophisticated techniques (e.g., UHV deposition, ion beam sputtering, and pulsed laser ablation) but can rather be induced simply through controlling the reductive synthesis conditions.
... The peaks broadening and shifting attributed to many factors viz. number of MoS 2 layers, elemental composition, formation of defective carbon, extension in van-der-walls interaction among layers and strain in layers [38]. The small peak around 281.6 cm − 1 with small intensity corresponds to E 1g, is due to MoS 2 curvature around MWCNTs [34]. ...
... While SnS 2 displays a high crystallite size (24.5 nm) with low micro-strain and dislocation density compared to other mono and bi-metallic chalcogenides. The lower crystallite size exhibits higher HER activity as it contains a large edge to the basal plane ratio which is caused by high active sites [43,44]. Theoretically, it is demonstrated that increased HER activity is caused by the d-band center of the S atom descending to the fermi level as a result of dislocation with a strain that reduces free energy to zero. ...
Cu2CoSnS4, Cu2SnS3, Cu2CoS4, Co2SnS3, Cu2S, CoS2, and SnS2 were synthesized using a one-step solvent-free solid-phase approach. The surface structure, morphology, and composition were characterized using an X-ray diffractometer (XRD), Fourier-Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), and X-ray Photoelectron Spectroscopy (XPS). The characterizations reveal pure phase formation and porous morphology. Further, the Hydrogen evolution reaction was performed using Cu2CoSnS4, Cu2SnS3, Cu2CoS4, Co2SnS3, Cu2S, CoS2, and SnS2-based electrodes. Amid all electrocatalysts, Cu2CoSnS4 shows an excellent hydrogen evolution reaction with a low overpotential of −192.1 mV at −10 mA/cm² in 0.5 M H2SO4. And higher current density. Cu2CoSnS4 also shows a lower Tafel slope of 98.6 mV/dec and charge transfer resistance than mono and bimetallic chalcogenide-based electrodes. The Cu2CoSnS4 exhibit very good stability for ∼22 h at −10 mA/cm² current density in 0.5 M H2SO4.
Amorphous, mixed-valency, molybdenum sulfide (MoSx) with a proposed formula, [Mo(IV)4Mo(V)2(S22–)3(S2–)5](SO4)5, was grown through a one-pot, solvothermal synthesis on multi-walled carbon nanotubes (MWCNTs) in a gram-scale setup. Optimizing the loading of the active catalyst relative to the conductive support resulted in optimized catalytic performance in hydrogen evolution reaction, reaching down to one of the lowest reported overpotentials, η10 = 140 mV and η100 = 198 mV with a Tafel slope of 62 mV/dec, for the 6.5 wt % of MoSx@MWCNTs. Engineering this amorphous MoSx catalyst was made possible through control of the oxidation state of Mo to avoid the fully reduced MoS2 phases. We also demonstrate that engineering defects in the MoSx catalyst does not require sophisticated techniques (e.g., UHV deposition, ion beam sputtering, and pulsed laser ablation) but can rather be induced simply through controlling the reductive synthesis conditions.
A thiomolybdate [Mo3S13]2- nanocluster is a promising catalyst for hydrogen evolution reaction (HER) due to the high number of active edge sites. In this work, thiomolybdate cluster films are prepared by spin-coating of a (NH4)2Mo3S13 solution both on FTO glass substrates as hydrogen evolving electrodes and on highly 00.1-textured WSe2 for photoelectrochemical water splitting. As an electrocatalyst, [Mo3S13]2- clusters demonstrate a low overpotential of 220 mV at 10 mA cm-2 in 0.5 M H2SO4 electrolyte (pH 0.3) and remain structurally stable during the electrochemical cycling as revealed by in situ Raman spectroscopy. Moreover, as a co-catalyst on WSe2, [Mo3S13]2- clusters enhance the photocurrent substantially by more than two orders of magnitude (from 0.02 to 2.8 mA cm-2 at 0 V vs RHE). The synergistic interactions between the photoelectrode and catalyst, i.e., surface passivation and band bending modification by the [Mo3S13]2- cluster film, promoted HER catalytic activity of [Mo3S13]2- clusters influenced by the WSe2 support, are revealed by intensity-modulated photocurrent spectroscopy and density functional theory calculations, respectively. The band alignment of the WSe2/[Mo3S13]2- heterojunction, which facilitates the electron injection, is determined by correlating UV-vis with photoelectron yield spectroscopy results.
Transition metal phosphides with high catalytic activity and durability for the hydrogen evolution reaction (HER) are promising candidates. Herein, we synthesized various Ni2P-Ru2P nano catalysts with different Ni/Ru ratio supported on chemically converted graphene (CCG) under 10 vol% H2/Ar2 atmosphere. The average size of Ni2P-Ru2P nanoparticles monotonously increases from 2.98 nm to 6.40 nm with the increase of reduction temperature from 500℃ to 800℃. Meanwhile, the ratio of Ru/Ni is also monotonically increase from 0.67 to 0.85 according to the X-ray photoelectron spectroscopy, suggesting the segregation of Ni to the surface. The Ni2P-Ru2P/CCG-800 shows the best performance for HER with low overpotentials of 21.83 mV (1 M KOH), 113.38 mV (1 M PBS) and 49.42 mV (0.5 M H2SO4), when the current density reaches 10 mA cm⁻². Besides, its Tafel slope of Ni2P-Ru2P/CCG-800 is 56.92 mV dec⁻¹ in 1 M KOH (67.85 mV dec⁻¹ in 1 M PBS, 45.98 mV dec⁻¹ in 0.5 M H2SO4). The superior HER activity of Ni2P-Ru2P/CCG-800 can be ascribed to the synergistic effect of Ni and Ru near surface. Density functional theory calculations reveal that the introduction of Ni atom into Ru2P accelerates H2O dissociation at Ru sites and H2 formation at Ni sites.
The chitosan/polyvinyl alcohol/halloysite nanoclay (CS/PVA/HNC) loaded with cephradine drug electrospun nanofibers (NFs) were fabricated and characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) techniques. FTIR analysis confirmed the hydrogen bonding between the polymer chain and the developed siloxane linkages. SEM analysis revealed the formation of uniform NFs having beads free and smooth surface with an average diameter in 50–200 nm range. The thermal stability of the NFs was increased by increasing the HNC concentration. The antimicrobial activity was examined against Escherichia coli and staphylococcus strains and the NFs revealed auspicious antimicrobial potential. The drug release was studied at pH 7.4 (in PBS) at 37 °C. The drug release analysis showed that 90% of the drug was released from NFs in 2 h and 40 min. Hence, the prepared NFs could be used as a potential drug carrier and release in a control manner for biomedical application.
