FlatChem最新文献

The characteristics of widely explored two-dimensional (2D) layered materials make them promising objects for structural functionalization to adjust their physical and chemical properties. The chemical functionalization of graphene family members has been reported to be useful in catalysis, although the efficiency of organic substitution of germanene, the newborn in the graphene family, remains limited and fairly attracts significant scientific attention. In this study, we explore the photoelectrochemical (PEC) activity of hydroxyalkyl germananes Ge_n-(CH₂)_n-OH (n = 2, 6, 10) through PEC-type photodetector experiments, employing excitation wavelengths ranging from 360 to 720 nm. Our findings reveal that organic substitution induces the opening of the germanane band gap, leading to a significant widening up to 2.38 eV and enhanced charge transfer kinetics under visible light irradiation.

Thermoelectric generation and photocatalytic water splitting to produce hydrogen are key measures to solve energy shortage and environmental pollution. In this work, we proposed three unexplored 2D materials, ZnAl₂S₄, ZnGa₂S₄ and ZnIn₂S₄, and further investigated their stability, thermoelectric and photocatalytic water splitting performance. We revealed the three single-layers possess low cleavage energies of 0.23–0.28 J/m², and simultaneously show high mechanical, thermal and dynamic stability. Besides, the single-layers are indirect semiconductors with band-gaps of 2.62/2.15/1.93 eV, and deliver thermoelectric power factors of 3.03/4.06/5.92 mW/K²m at 300 K. Also, due to the high nonlinear phonon dispersion and strong acoustic-optical interactions, they have high phonon scattering rates, as well as low lattice thermal conductivities of 1.11–3.06 W/mK. As a result, their thermoelectric figure of merit can reach 0.12/0.11/0.10 at 300 K, and increases to 0.77/0.69/0.66 at 700 K. Moreover, they also have suitable REDOX band-edges, which can drive photocatalytic water splitting to produce hydrogen and oxygen, and show high absorption coefficients of ∼ 10⁵ cm⁻¹ from visible to ultraviolet.

Photoelectrochemical (PEC) sensing platforms demonstrate outstanding performances towards enzyme-free glucose detection, and exploring glucose reactive electrodes with efficient active sites and enhanced carrier transport/separation behavior would be beneficial for PEC glucose detection. Herein, we fabricated two-dimensional Cu₃(PO₄)₂ nanosheets as the photoactive material for glucose detection. The morphology and structural characterizations prove the existence of balanced Cu⁰–Cu⁺ active sites which has been regarded as the key factor on improving PEC performance for fast glucose detection. The photocurrent of Cu₃(PO₄)₂ nanosheets is three times that of Cu₃(PO₄)₂ bulk in the absence of glucose, and the response performance is increased by about 9 times compared to Cu₃(PO₄)₂ bulk at 50 µM glucose. Under light conditions, the limit of detection (LOD) as low as 17.68 µM at low concentration of 20–100 µM, and LOD of 131.69 µM at high concentration of 100–1000 µM can be achieved. This work might provide the basic understanding and new opportunities in applying two-dimensional Cu₃(PO₄)₂ nanosheets for glucose detection.

Graphene-based materials have been researched to substitute traditional Pt-based electrocatalysts in the hydrogen evolution reaction (HER) due to its strong electrical conductivity, easy functionalization, and cheaper synthesis. Doping graphene with heteroatom is a simple way of obtaining original and active electrocatalysts. Moreover, the nitrogen on it had a positive effect on HER performance. By using a reducing agent with nitrogen while synthesising graphene-based aerogels nitrogen-doped catalysts were obtained. In addition, a better reduction rate, higher crystallography parameters and a more porous material structure were reached. The aerogels were synthesised in an one-pot hydrothermal process, in which the graphene sheets were assembled. This was followed by freeze-drying, which fixed the carbon matrix structure. As a result, the final aerogel had a 3D structure that eased mass transfer and enhanced catalytic activity, reaching an overpotential of −10 mAcm⁻² at 101 mV vs RHE (η₁₀ = 101 mV). The amount of quaternary type nitrogen generated during synthesis had a strong influence on electrocatalytic behaviour in HER. Then, quaternary nitrogen and surface area (up to 397 m²/g) were maximized to ensure a higher current density. Moreover, an effective aerogel was prepared with half the solvent per batch, as this was essential for expanding the synthesis to an industrial scale. A final calcination step resulted crucial to improve the metal-free aerogel HER performance.

The current research work is based on the synthesis of BiVO₄ (BVO), Bi₂S₃ (BS), a binary composite of BiVO₄ and Bi₂S₃ (BVO-BS), and MXene-based ternary nanocomposite of BiVO₄ and Bi₂S₃ (BVO-BS/MXene). BVO nanoparticles and BS nanorods were synthesized by co-precipitation and hydrothermal approaches respectively. While the binary (BVO-BS), and ternary (BVO-BS/MXene) nanocomposites were synthesized by an ultra-sonication method. The fabricated semiconducting materials were characterized by X-ray diffraction analysis, Fourier transforms infrared spectroscopy, and Scanning electron microscopy. Furthermore, the optical and electrochemical properties of synthesized samples were studied by UV–visible spectroscopy and Mott-Schottky/Electrochemical impedance spectroscopy analysis respectively. The photocatalytic removal efficiency of prepared samples was tested against an organic dye (Congo red) and pharmaceutical drug (Ciprofloxacin). The experimental results showed that (BVO-BS/MXene) ternary nanocomposite removed 92.5% congo red and 36.95% ciprofloxacin from wastewater under the visible light irradiation of about 70 min. While the binary composite; BVO-BS removed only 71.30% congo red and 22.61% ciprofloxacin within 70 min of irradiation. This outstanding degradation ability of BVO-BS/MXene for both Congo red and Ciprofloxacin as compared to binary composite (BVO-BS) was due to its large surface area, low charge transfer resistance (R_ct = 0.96 ohm), and low electron-hole pair recombination. Hence, BVO-BS/MXene is a novel and promising photocatalytic material that could be used as an efficient photocatalyst for environmental pollution remediation applications.

Theoretical innovations for constructing robust computational protocols are of fundamental significance for a variety of advanced chiroptical spectroscopies. The new generation of chiral curved nanographenes offered us the opportunity to study the chiral emission phenomena in the nanometers scale. Herein we reported a distinctive method that combines topological aspects and the density functional theory in order to reach a coherent description of calculated circularly polarized luminescence spectra of negatively curved nanographenes. Our computational plan was defined as a multi-sequence strategy, paying the attention on the relationship between the molecular curvature and the relative spectroscopic properties: 1) the Ball Pivoting Algorithm for the nanographene surface reconstruction; 2) the atom by atom discrete gaussian curvature analysis to establish which DFT functional better approximates the shape of nanographenes backbones; 3) molecular dynamics in the first excited state for accounting the thermal effect; 4) TDDFT benchmark to scrutinize which functional provides the most reliable excitation energies and rotatory strengths for an accurate CPL spectral simulation. The direct merging of the previous steps celebrated the B3LYP (coupled with the 6-311G(d,p) basis set) as the most precise exchange–correlation functional in duplicating exquisitely the CPL profiles of a heterogeneous set of functionalized nanographene.

nZVI materials loaded on GO have been applied to the treatment of difficult-to-degrade organics due to their higher electron transfer rate. However, cobalt doping of GO/nZVI composites and the effect of the doped materials on difficult-to-degrade organics are not known. In this work, Cobalt-doped Graphene-supported nanoscale Zero-valent Iron (GO/nZVI-Co) was successfully synthesized via the liquid-phase reduction-suspension self-assembly method, which was composited with theoretical mass ratio of GO:nZVI:Co = 1:2:0.08. And GO/nZVI-Co was used as efficient heterogeneous catalyst for degradation of Rhodamine B (RhB) via H₂O₂. Characterization results show that nZVI and Co particles were successfully loaded on GO nanosheets increasing the dispersibility of particles. Under the optimal reaction conditions(the mass ratio of GO: nZVI = 1:2 and Co doping is less than 1/5), the RhB degradation rate was as high as 98.28 %. The degradation pathways of GO/nZVI-Co-HP system could better explained by the secondary kinetic model and GC–MS spectru. The main effect of cobalt doping in the GO/nZVI-Co-HP system is to increase the adsorption properties of the material on H₂O₂, and this facilitates the contact reaction of nZVI with H₂O₂. In this study, a GO/nZVI-Co material with improved electron transfer efficiency was prepared and its removal mechanism of pollutants was elucidated to provide relevant theoretical support for the treatment of difficult-to-degrade wastewater.

Hydrogen evolution by water splitting is one of the most popular methods in the new generation energy exploration. During the hydrogen evolution reaction (HER), NiS₂, which is an electrochemical catalyst, has been widely investigated. However, the electrochemical catalytic performance of NiS₂-based catalysts is still dissatisfied due to their relatively poor intrinsic catalytic activities. Herein, we introduced vacancies into NiS₂ nanosheets and the activation of initial inert sulfur sites by He⁺ ion irradiation (at a dose of 1 × 10¹⁵/cm²) to improve the HER electrocatalytic performance of NiS₂. Additionally, density functional theory (DFT) calculations were adopted. Clearly, the intrinsic vacancies (both Ni and S vacancies) of NiS₂ can reduce the band gap of NiS₂ and improve its electron transfer efficiency in the HER process. This work provides a candidate strategy for NiS₂-based electrocatalysts to optimize HER performance.

Electrocatalytic hydrogen production is an effective way to produce hydrogen energy, and the key is to find inexpensive and effective catalysts. Loading transition metal sulfides onto two-dimensional transition metal carbide (MXene) is an effective method to prepare cheap and high-performance hydrogen evolution reaction (HER) catalysts. In this study, Mo₂TiAlC₂ was etched with hydrofluoric acid to prepare Mo₂TiC₂T_x MXene, which was then composited with MoS₂ and CoS₂ to prepare defect-rich MoS₂/CoS₂@Mo₂TiC₂T_x composite by a hydrothermal method. MoS₂/CoS₂ provides a large number of active sites for electrocatalysis, while Mo₂TiC₂T_x MXene as a carrier not only provides nucleation and growth sites for MoS₂/CoS₂, but also increases the rate of electron transfer in HER process, which achieves good synergy between MoS₂/CoS₂ and Mo₂TiC₂T_x MXene. Consequently, MoS₂/CoS₂-2@Mo₂TiC₂T_x exhibits an excellent HER performance. When the current density reaches 10 mA cm⁻², the optimal MoS₂/CoS₂-2@Mo₂TiC₂T_x catalyst only requires an overpotential of 80 mV, and exhibits good cycling stability and durability. This work gives a new idea for the preparation of efficient HER catalysts using non-precious metal composites to replace the precious Pt/C.

Electrochemical hydrogen evolution reaction (HER) is an emerging research domain aiming to supply a means of renewable energy. Transition metal dichalcogenides (TMDs) have a good potential as promising low-cost alternatives to platinum-based catalysts. Molybdenum disulfide (MoS₂) nanostructures with different shapes are increasingly becoming attractive materials for HER electrocatalysis, thanks to their peculiar physical properties which depend on their composition and morphology. It is still challenging to produce MoS₂ nanomaterials simply and straightforwardly. In this work, MoS₂ nanoensembles and small nanoparticles were fabricated via facile solvothermal protocols. The produced structures display a competitive activity in HER, with the nanoensembles performing better than the isotropic particles. This was attributed to the abundance of their electrochemically active sites and their robust structural stability, which endowed them with remarkable endurability in electroactivity. The nanoensemble morphology ensured the creation of a well-connected array of channels for charge transport, thus favouring an ameliorated electrochemical activity.