FlatChem最新文献

Metal chalcogenides like Tin sulfide (SnS₂) presents as viable alternative electrocatalysts for alkaline water splitting (AWS) due to their huge abundance, stability, and environment friendly nature. However, insufficient exposed active sites and poor conductivity severely impede its large-scale applications. In this work, an in-situ hybridization of hexagonal SnS₂ with intercalation of reduced graphene oxide nanosheets (TS-rGOx) overcomes the problem of SnS₂ stacking. It further enhances the interlayer spacing thereby boosting the number of active sites. The resulting TS-rGOx exhibited excellent oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities demanding low overpotential of 313 mV and 196.2 mV at 20 mA/cm² with long term durability upto 60 h, which can be attributed to enhanced interlayer spacing of SnS₂, abundant active sites and higher conductivity resulting from the in-situ hybridization and intercalation of rGO nanosheets. This work opens a prospect towards the design and application of efficient SnS₂ based heterostructured electrocatalyst for AWS.

Exfoliated 2H-MoS₂ holds a promising future for various electrochemical applications. Nevertheless, its electrical conductivity and electrocatalytic efficiency are limited, restricting its standalone use. To address this limitation, this study proposes the electrochemical deposition of gold nanoparticles on layer-by-layer films of poly(diallyl dimethylammonium) hydrochloride interspersed with exfoliated 2H-MoS₂, previously assembled on ITO substrate. This modified electrode, denoted as ITO/PDAC/2H-MoS₂/Au, was assessed for its effectiveness in the voltametric detection of bisphenol-A (BPA). The optimal electrode architecture demonstrated a linear BPA detection range (0.9 µM-19 µM; R² > 0.99), with a limit of detection of 23 nM. Notably, the electrochemical deposition was effective on both bare and film modified ITO substrates. However, it was on the ITO/PDAC/2H-MoS₂/Au electrode that BPA detection achieved a reasonable level of sensitivity. During electrodeposition, superficial Mo(IV) is oxidized to Mo(VI) while sulfur vacancies are generated. These defect sites enhance the electrochemical activity of 2H-MoS₂ and play a pivotal role in nucleating, growing, and immobilizing gold nanoparticles, which collectively enhance the sensor’s performance.

Molybdenum disulfide (MoS₂) has been immensely explored for its potential usage in energy storage applications owing to its high theoretical specific capacitance and layered structure. Here, we have investigated the effect of selenium addition in MoS₂ forming MoS_2(1-x)Se_2x alloys and studied their electrochemical performance. Selenization was performed through a simple hydrothermal method. The electrochemical performance of MoS₁Se₁ was evaluated in a two-electrode configuration. The selenization is found to improve the electrochemical performance of MoS₂ and the MoS₁Se₁ alloy with the optimal S (sulfur) to Se (selenium) ratio of 1:1 exhibits an excellent areal capacitance of 2629.45 mF/cm² at 1 mA/cm², with an appreciable specific capacitance of 266.51 F/g at a current density of 0.5 A/g and excellent cycle stability of 81.64 % after 6000 cycles. Along with the experimental findings, Density functional theory calculations were also performed, revealing that the electronic properties of MoSSe systems can be tuned by varying the ratio of S and Se.

Interface engineering plays a critical role in the development of high-efficient fuel cell catalysts, as the interfaces across different components can synergistically and substantially accelerate electrocatalysis kinetics, together with improvement in mass transfer and structural stability. In this study, we report a feasible strategy to create PdPtAg-on-Au heterogenous nanoplates (PdPtAg-on-Au HNPs) and validate their structural advantages in electrocatalysis. By limiting the doping of Au nanoplates with Pt/Ag atoms on the surface and subsequently depositing Pd nanodots in a highly scattered pattern, abundant multimetallic interfaces form and enhance the methanol oxidation reaction (MOR) electrocatalytic process. The optimized PdPtAg-on-Au HNPs/C electrocatalysts exhibited superior mass activity, improved reaction kinetics, and long-term durability compared to commercial Pt/C. DFT simulations suggest that the chemical surrounding of the Pd/Pt catalytic active center with AuAg atoms can lower the reaction barrier and CO binding affinity. This work provides a feasible synthetic strategy for preparing multimetallic fuel cell electrocatalysts with advanced control over heterogeneous structures, highlighting the potential of interface engineering in the rational design of electrocatalysts.

Laser-induced graphene (LIG) on paper is a popular choice for fabricating flexible micro-supercapacitors (MSCs) as it is a simple and sustainable process. However, carbon-based MSC electrodes have limited energy densities. To address this challenge, this study presents a highly reproducible and cost-effective method for decorating manganese oxide (MnO_x) on interdigital LIG MSC electrodes, fabricated via a single-step direct laser writing (DLW) process on paper substrates. The paper fibers embedded with MnO_x precursors are transformed into graphene through laser processing while reducing the salt, resulting in the formation of MnO_x-LIG. The resulting MnO_x-LIG-MSC exhibits a specific capacitance of 12.30 mF cm⁻² (0.05 mA cm⁻²) with a 60 % retention at 1000 bending cycles (30°), due to the pseudocapacitive contribution of MnO_x. Furthermore, the devices exhibit high electrochemical stability, retaining 190 % of the initial specific capacitance after 10,000 cycles, and a high energy density of 2.6 μWh cm⁻² (at a power of 0.109 mW cm⁻²). The study demonstrates that manganese oxide-based LIG-MSCs have the potential to be used as energy storage devices for portable, low-cost, and flexible paper electronics.

Functional groups based on halides, such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), are crucial for understanding the chemical reactivity of graphitic nanomaterials. Except for I, halogens exhibit electronegativity greater than carbon (C); therefore, charge transfer from carbon to halogen is expected. First-principles density functional theory calculations were performed to determine the role of different Cl-functional groups (methyl-trichloride, ethyl-trichloride, chloride, acyl-chloride, vinyl-chloride, acetyl hypochlorite, chloramines, sulfonyl chloride, and more) on the electronic properties of graphene and graphene nanoribbons (GNRs). GNRs with zigzag edges (ZGNRs) and armchair edges (AGNRs) were studied. We analyzed the optimized structures, band structure, density of states, cohesive energy, and band gap. Our results revealed that the based-Cl functional groups can provide an alternative route to activate the borders and surfaces of sp² carbon materials. Methyl-trichloride and acyl-chloride can induce magnetism and metallicity. Chloride and acyl-chloride are the most energetically stable functional groups attached to the edges. Surprisingly, methyl-trichloride or acyl-chloride functionalizing the surface of the AGNRs showed a direct (indirect) band gap for states with spin-up (spin-down). The results of aromatic (chlorobenzene- and dichlorobenzene-like structures) functionalization considering F, Cl, Br, and I are also shown. Finally, –F₂ and –ClF functionalization cases are discussed.

In this work, the development of a graphene quantum dots (GQDs)-modified screen-printed carbon (SPCE) electrode for the determination of cannabidiol (CBD), a cannabinoid present in the Cannabis L. Sativa (hemp) plant, is reported. This cannabinoid is non-intoxicating and non-psychoactive, thus CBD-containing drugs as well as CBD-containing foods, are now on the market in many countries due to their health-beneficial effects and pharmacological activities. Because of the increasing interest in analyzing CBD in these real samples, we analyzed here a sample of hemp flour that was used for testing the developed CBD electrochemical sensor. Preliminary work devoted to optimizing the analysis conditions, allowed to development of a GQDs-modified electrode with promising characteristics for the simple screening of CBD. The electroanalytical tests for CBD detection showed a sensitivity of 0.98 μAμM^-1 cm⁻², which is increased by 2-folder compared to bare SPCE, and a limit of detection (LOD) equal to 0.277 μM. The developed GQDs/SPCE sensor and the analysis procedure were then applied for the CBD analysis in a hemp seeds flour sample. Based on the results obtained, the advantages/disadvantages evidenced by operating with the developed electrochemical sensor in the analysis of CBD in real samples were discussed.

Friction and wear pose significant challenges in moving mechanical systems. Despite efforts to address these challenges with MAX phase materials, many of these materials lack effective lubrication and wear protection under ambient conditions. Here, we developed a composite coating that addresses these challenges through a combination of materials chemistry and engineering. This coating, composed of polydopamine-functionalized Ti₃AlC₂ MAX (F-MAX) and multilayer graphene (MGr), known as F-MAX + MGr, demonstrated exceptional tribological performance. At its best composition, the F-MAX + MGr composite coating reduced the friction at sliding interfaces by 82 % and decreased the wear on the counterpart ball by 99.76 % compared to bare surfaces. Importantly, its tribological performance surpassed that of pristine MAX, F-MAX, and MGr coatings. This improvement is attributed to the synergistic lubricating effect of the inherently low shear strengths of Ti₃AlC₂ MAX and MGr, the chemical properties of PDA, and the occurrence of incommensurate contacts at the interfaces. This work pioneers slippery and wear-resistant surfaces via a combination of chemical modification and materials engineering, with implications for both fundamental science and technological advancement.

In this paper, the adsorption capacity of intrinsic penta-BAs₅ monolayer on CO, NH₃, NO, SO₂ and the effect of transition metal doping on gas sensing characteristics are systematically studied by first-principles calculations. Adsorption energy, recovery time, band structure, charge transfer and density of states (DOS) are investigated. The electronic properties and sensing mechanisms under different adsorption systems are expounded. The results showed that the intrinsic penta-BAs₅ monolayer had the strongest adsorption capacity for NO and weak sensitivity to CO, NH₃ and SO₂, which shown strong gas selectivity. Moreover, the recovery time of NO at 380 k was 3.93 s, which was more inclined to be desorption at high temperature. In addition, Sc and Ti doping could selectively improve the adsorption capacity of the intrinsic penta-BAs₅ monolayer. The charge transfer of SO₂-Sc-BAs₅ and CO-Ti-BAs₅ were increased by 6.78 and 10.33 times compared with those before doping. The band structure and DOS show that Ti atom and CO have orbital hybridization, which improved the interaction between gases and penta-BAs₅. Therefore, intrinsic penta-BAs₅, Sc-BAs₅ and Ti-BAs₅ are suitable for gas sensing and toxic gas monitoring, and have broad application prospects.

Graphitic carbon nitride as a photocatalyst seeking attention nowadays, due to its thermal stability, band structure, and chemical properties. Herein, we reported a boron sulfur co-doped graphitic carbon nitride (B@S-g-C₃N₄) photocatalyst synthesized by a one-pot thermal polycondensation mechanism. However, it was observed that due to co-doping in native carbon nitride structure the photocatalytic behavior and the band structure enhanced which was capable of fascinating the demand of organic transformations i.e. photocatalytic and charge transfer capability. The synthesized B@S-g-C₃N₄ photocatalyst was characterized by UV–vis DRS, FT-IR, XRD, SEM, EDX, HR-TEM, XPS and electrochemical properties. In addition, the synthesized B@S-g-C₃N₄ photocatalyst is a metal-free carbon nitride photocatalyst proven to be highly effective in performing organic transformations (conversion yield 98 %) like C-N bond formation under visible light source.