Decoration of MoS2 on g-C3N4 surface for efficient hydrogen evolution reaction

One-step hydrothermal synthesis of CuS/MoS2 composite for use as an electrochemical non-enzymatic glucose sensor

Early diagnosis may be crucial for the prevention of chronic diabetes mellitus. For that herein, we prepared a CuS/MoS2 composite for a non-enzymatic glucose sensor through a one-step hydrothermal method owing to the synergetic effect of CuS/MoS2. The surface morphology of CuS/MoS2 was studied by Field Emission Scanning Electron Microscopy (FESEM) and Cs-corrected Scanning Transmission Electron Microscopy (Cs-STEM). The crystallinity and surface composition of CuS/MoS2 were analyzed by X-ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) respectively. The working electrode was prepared from CuS/MoS2 electrocatalyst, and for that dispersed solution of electrocatalyst was used to fabricate the material-loaded glassy carbon electrode (GC). CuS/MoS2 composite shows the viability of electrocatalyst to oxidize glucose in an alkaline solution with sensitivity and detection limit of 252.71 μA mM-1 cm-2 and 1.52 μM respectively. The proposed glucose sensor showed reasonable stability and potential selectivity during electrochemical analysis. Accordingly, the CuS/MoS2 composite has potential as a viable material for glucose sensing in diluted human serum.

High interfacial charge separation in visible-light active Z- scheme g-C3N4/MoS2 heterojunction: Mechanism and degradation of sulfasalazine

Examination of highly proficient photoactive materials for the degradation of antibiotics from the aqueous solution is the need of the hour. In the present study, a 2D/2D binary junction GCM, formed between graphitic-carbon nitride (g-C3N4) and molybdenum disulphide (MoS2), was synthesized using facile hydrothermal method and its photo-efficacy was tested for the degradation of sulfasalazine (SUL) from aqueous solution under visible-light irradiation. Morphological analysis indicated the nanosheets arrangement of MoS2 and g-C3N4. The visible-light driven experiments indicated that 97% antibiotic was degraded by GCM-30% within 90 min which was found to be quite high than pristine g-C3N4 and MoS2 at solution pH of 6, GCM-30% dose of 20 mg, and SUL concentration of 20 mgL-1. The degradation performance of GCM-30% was selectively improved due to enhanced visible-light absorption, high charge carrier separation, and high redox ability of the photogenerated charges which was induced by the effective Z-scheme 2D/2D heterojunction formed between g-C3N4 and MoS2. The reactive radicals as determined by the scavenging study were •O2-, and h+. A detailed degradation mechanism of SUL by GCM-30% was also predicted based on the detailed examination of the band gaps of g-C3N4 and MoS2.

New g-C3N4/GO/MoS2 composites as efficient photocatalyst for photocathodic protection of 304 stainless steel

Photocathodic protection is an economical and environmental metal anticorrosion method. In this research, we successfully synthesized the g-C₃N₄/GO (15 wt%)/MoS₂ catalytic materials by a facile hydrothermal method. The results show that the as-prepared g-C₃N₄/GO (15 wt%)/MoS₂ composites prominently enhanced photocatalytic activities for the photocathodic protection of 304 stainless steel (SS) compared with the corresponding pristine g-C₃N₄ and MoS₂. Notably, the AC impedance results demonstrated that the Rct value of 304 SS coupled with g-C₃N₄/GO (15 wt%)/MoS₂ decreased to 35.66 Ω•cm², which is 29 and 37 times lower than that of g-C₃N₄ and MoS₂ alone. In addition, g-C₃N₄/GO (15 wt%)/MoS₂ provided the highest current density (77.19 μA•cm²) for the 304 SS, which is four times that of pristine g-C₃N₄. All results indicate that as-prepared g-C₃N₄/GO (15 wt%)/MoS₂ photocatalysts have produced a distinct enhancement on photocathodic protection performance. An optimum decorating amount of MoS₂ onto g-C₃N₄ forms heterojunctions of g-C₃N₄/MoS₂, which favor the separation of electrons and holes efficiently. Furthermore, the addition of GO further promotes the separation and transfer of photo-induced carriers.

Doping of MoS2 by "Cu" and "V": An Efficient Strategy for the Enhancement of Hydrogen Evolution Activity

To replace Pt-based compounds in the electrocatalytic hydrogen evolution reaction (HER), MoS₂ has already been established as an efficient catalyst. The electrocatalytic activity of MoS₂ is further improved by tuning the morphology and the electronic structure through doping, which helps the band energy position to be modified. Presently, thin sheets of MoS₂ (MoS₂-TSs) are synthesized via a microwave technique. Thin sheets of MoS₂ can outperform nanosheets of MoS₂ in the HER. Further, the efficiency of the thin sheets is improved by doping with different metals like Cu, V, Zn, Mn, Fe, Sn, etc. "Cu"- and "V"-doped MoS₂-TSs are highly efficient for the HER. At a fixed potential of -0.588 V vs RHE, Cu-doped MoS₂ (Cu-MoS₂-TS), V-doped MoS₂ (V-MoS₂-TS), and MoS₂-TS can generate current densities of 327.46, 308.45, and 127.82 mA/cm², respectively. The electrochemically active surface area increases nearly 7.7-fold and 2.5-fold for Cu-MoS₂-TS and V-MoS₂-TS than for MoS₂-TS, respectively. Cu-MoS₂-TS shows exceptionally high electrocatalytic stability up to 140 h in an acidic medium (0.5 M H₂SO₄). First-principles calculations using density functional theory (DFT) are performed, which are well matched with the experimental observations. DFT calculations dictate that after doping with "V" and "Cu" both valance band maxima and conduction band minima are uplifted, which indicates the higher hydrogen-ion-reducing ability of M-MoS₂-TS (M = Cu, V) compared to bare MoS₂-TS.

Polydopamine-Assisted Two-Dimensional Molybdenum Disulfide (MoS2)-Modified PES Tight Ultrafiltration Mixed-Matrix Membranes: Enhanced Dye Separation Performance

Tight ultrafiltration (TUF) membranes with high performance have attracted more and more attention in the separation of organic molecules. To improve membrane performance, some methods such as interface polymerization have been applied. However, these approaches have complex operation procedures. In this study, a polydopamine (PDA) modified MoS₂ (MoS₂@PDA) blending polyethersulfone (PES) membrane with smaller pore size and excellent selectivity was fabricated by a simple phase inversion method. The molecular weight cut-off (MWCO) of as-prepared MoS₂@PDA mixed matrix membranes (MMMs) changes, and the effective separation of dye molecules in MoS₂@PDA MMMs with different concentrations were obtained. The addition amount of MoS₂@PDA increased from 0 to 4.5 wt %, resulting in a series of membranes with the MWCO values of 7402.29, 7007.89, 5803.58, 5589.50, 6632.77, and 6664.55 Da. The MWCO of the membrane M3 (3.0 wt %) was the lowest, the pore size was defined as 2.62 nm, and the pure water flux was 42.0 L m⁻² h⁻¹ bar⁻¹. The rejection of Chromotrope 2B (C2B), Reactive Blue 4 (RB4), and Janus Green B (JGB) in aqueous solution with different concentrations of dyes was better than that of unmodified membrane. The separation effect of M3 and M0 on JGB at different pH values was also investigated. The rejection rate of M3 to JGB was higher than M0 at different pH ranges from 3 to 11. The rejection of M3 was 98.17–99.88%. When pH was 11, the rejection of membranes decreased with the extension of separation time. Specifically, at 180 min, the rejection of M0 and M3 dropped to 77.59% and 88.61%, respectively. In addition, the membrane had a very low retention of salt ions, Nacl 1.58%, Na₂SO₄ 10.52%, MgSO₄ 4.64%, and MgCl₂ 1.55%, reflecting the potential for separating salts and dyes of MoS₂@PDA/PES MMMs.

Aggregates of Ni/Ni(OH)2/NiOOH Nanoworms on Carbon Cloth for Electrocatalytic Hydrogen Evolution

The development of an efficient electrocatalyst for hydrogen evolution reaction (HER) is essential to facilitate the practical application of water splitting. Here, we aim to develop an electrocatalyst, Ni/Ni(OH)₂/NiOOH, via electrodeposition technique on carbon cloth, which shows efficient activity and durability for HER in an alkaline medium. Phase purity and morphology of the electrodeposited catalyst are determined using powder X-ray diffraction and electron microscopic techniques. The compositional and thermal stability of the catalyst is checked using X-ray photoelectron spectroscopy and thermogravimetry analysis. Electrodeposited Ni/Ni(OH)₂/NiOOH material is an efficient, stable, and low-cost electrocatalyst for hydrogen evolution reaction in a 1.0 M KOH medium. The catalyst exhibits remarkable performance, achieving a current density of 10 mA/cm² at a potential of -0.045 V vs reversible hydrogen electrode (RHE), and the Tafel slope value is 99.6 mV/dec. The overall electrocatalytic water splitting mechanism using Ni/Ni(OH)₂/NiOOH catalyst is well explained, where formation and desorption of OH^- ion on the catalyst surface are significant at alkaline pH. The developed electrocatalyst shows significant durability up to 200 h in a negative potential window in a highly corrosive alkaline environment along with efficient activity. The electrocatalyst can generate 165.6 μmol of H₂ in ∼145 min of reaction time with 81.5% faradic efficiency.

Electrocatalytic Performance of Titania Nanotube Arrays Coated with MoS2 by ALD toward the Hydrogen Evolution Reaction

The electrochemical splitting of water provides an elegant way to store renewable energy, but it is limited by the cost of the noble metals used as catalysts. Among the catalysts used for the reduction of water to hydrogen, MoS₂ has been identified as one of the most promising materials as it can be engineered to provide not only a large surface area but also an abundance of unsaturated and reactive coordination sites. Using Mo[NMe₂]₄ and H₂S as precursors, a desired thickness of amorphous MoS₂ can be deposited on TiO₂ nanotubes by atomic layer deposition. The identity and structure of the MoS₂ film are confirmed by spectroscopic ellipsometry, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The electrocatalytic performance of MoS₂ is quantified as it depends on the tube length and the MoS₂ layer thickness through voltammetry, steady-state chronoamperometry, and electrochemical impedance spectroscopy. The best sample reaches 10 mA/cm² current density at 189 mV overpotential in 0.5 M H₂SO₄. All of the various geometries of our nanostructured electrodes reach an electrocatalytic proficiency comparable with the state-of-the-art MoS₂ electrodes, and the dependence of performance parameters on geometry suggests that the system can even be improved further.

MoS2/CdS Heterostructure for Enhanced Photoelectrochemical Performance under Visible Light

High-rate recombination of photogenerated electron and hole pairs will lead to low photocatalytic activity. Constructing heterostructure is a way to address this problem and thus increase the photoelectrochemical performance of the photocatalysts. In this article, molybdenum sulfide (MoS2)/cadmium sulfide (CdS) nanocomposites were fabricated by a facile solvothermal method after sonication. The CdS nanoparticles immobilized on the MoS2 sheet retained the original crystal structure and morphology. The composites exhibit higher photoelectrochemical properties compared with pure MoS2 nanosheets or CdS powder. When the precursor concentration of CdS is 0.015 M, the MoS2/CdS composites yield the highest photocurrent, which is enhanced nearly five times compared with pure CdS or MoS2. The improved photoelectrochemical performance can be ascribed to the increase of light harvest, as well as to the heterostructure that decreases the recombination rate of the photogenerated electron and hole pairs.

Novel design of hollow g-C3N4 nanofibers decorated with MoS2 and S, N-doped graphene for ternary heterostructures

Herein, we newly design 1-dimensional ternary structure of HGCNF/MoS₂/SNG via a one-pot hydrothermal treatment at relatively low temperature and showed a higher double layer capacitance with HER activity.

A core@shell hollow heterostructure of Co3O4 and Co3S4: an efficient oxygen evolution catalyst

A hollow core@shell nanostructure of Co₃O₄ and Co₃S₄ helps to enhance the electrocatalytic activity for the OER.