Amorphous cobalt boride nanosheets anchored surface-functionalized carbon nanofiber: An bifunctional and efficient catalyst for electrochemical sensing and oxygen evolution reaction

Temperature-Induced Conversion of 2D Vanadium-Doped MoSe2 Nanosheets to 1D V2MoO8 Rods: Enhanced Performance in Electrochemical Antibiotic Detection in Biological and Environmental Samples

In this work, new strategies were developed to prepare 1D-V2MoO8 (VMO) rods from 2D V-doped MoSe2 nanosheets (VMoSe2) with good control over morphology and crystallinity by a facile hydrothermal and calcination process. The morphological changes from 2D to 1D rods were controlled by changing the calcination temperature from 300 to 600 °C. The elimination of Se and the incorporation of O into the V-Mo structure were evaluated by TGA, p-XRD, Raman, FE-SEM, EDAX, FE-TEM, and XPS analyses. These results prove that the optimization of the physical parameters leads to changes in the crystal phase and textural properties of the prepared material. The VMoSe2 and its calcined products were investigated as electrochemical sensors for the detection of the antibacterial drug nitrofurantoin (NFT). At a calcination temperature of 500 °C, the modified screen-printed carbon electrodes (SPCE) proved to be an excellent electrochemical sensor for the detection of NFT in neutral media. Under the optimized conditions, VMO-500 °C/SPCE exhibits low detection limit (LOD) (0.015 μM), wide linear ranges (0.1-31, 47-1802 μM), good sensitivity, and selectivity. The proposed sensor was successfully used for the analysis of NFT in real samples with good recovery results. Moreover, the reduction potential of NFT agreed well with the theoretical analysis using quantum chemical calculations, with the B3LYP with 6-31G(d,p) basis set predicting an E0 value of -0.45 V. The interaction between the electrode surface and NFT via the LUMO diagram and the electrostatic potential surface is also discussed.

Composite of a thiacalix[4]arene-copper(I) metal-organic framework and mesoporous carbon for efficient electrochemical detection of antibiotics

Abundant use of nitrofurantoin (NFT) and metronidazole (MTZ) antibiotics has led to excessive residues in the environments and humans, resulting in serious damage to the human body and ecosystem. Therefore, effective detection of NFT and MTZ is exceedingly necessary. In this regard, metal-organic frameworks (MOFs) are promising materials as electrochemical sensors. Herein, we synthesized a new two-dimensional thiacalix [4]arene-copper (I) MOF (Cu-TC4A-M). This MOF was mixed with mesoporous carbon (MC) to a give Cu-TC4A-M@MC composite. In addition, the sensors of Cu-TC4A-M@MC(2:1)/GCE and Cu-TC4A-M@MC(1:2)/GCE were achieved (GCE = glassy carbon electrode), and then were applied for effectively detecting NFT and MTZ, respectively. Markedly, the two sensors exhibited satisfactory linear detection range, anti-interference, reproducibility and stability. When they were utilized in the real samples, such as human serum, urine, tap water and lake water, satisfactory recoveries were attained. The relative standard deviations (RSDs) were in the range of 1.16 % ∼ 1.92 % for NFT and 0.95 % ∼ 2.33 % for MTZ. This work provided a new application prospect for the thiacalix [4]arene-based MOFs as promising candidate materials for NFT and MTZ detection.

A Review of Transition Metal Boride, Carbide, Pnictide, and Chalcogenide Water Oxidation Electrocatalysts

Transition metal borides, carbides, pnictides, and chalcogenides (X-ides) have emerged as a class of materials for the oxygen evolution reaction (OER). Because of their high earth abundance, electrical conductivity, and OER performance, these electrocatalysts have the potential to enable the practical application of green energy conversion and storage. Under OER potentials, X-ide electrocatalysts demonstrate various degrees of oxidation resistance due to their differences in chemical composition, crystal structure, and morphology. Depending on their resistance to oxidation, these catalysts will fall into one of three post-OER electrocatalyst categories: fully oxidized oxide/(oxy)hydroxide material, partially oxidized core@shell structure, and unoxidized material. In the past ten years (from 2013 to 2022), over 890 peer-reviewed research papers have focused on X-ide OER electrocatalysts. Previous review papers have provided limited conclusions and have omitted the significance of "catalytically active sites/species/phases" in X-ide OER electrocatalysts. In this review, a comprehensive summary of (i) experimental parameters (e.g., substrates, electrocatalyst loading amounts, geometric overpotentials, Tafel slopes, etc.) and (ii) electrochemical stability tests and post-analyses in X-ide OER electrocatalyst publications from 2013 to 2022 is provided. Both mono and polyanion X-ides are discussed and classified with respect to their material transformation during the OER. Special analytical techniques employed to study X-ide reconstruction are also evaluated. Additionally, future challenges and questions yet to be answered are provided in each section. This review aims to provide researchers with a toolkit to approach X-ide OER electrocatalyst research and to showcase necessary avenues for future investigation.

Development of an Amorphous Nickel Boride/Manganese Molybdate Heterostructure as an Efficient Electrode Material for a High-Performance Asymmetric Supercapacitor

The exploration of heterostructure materials with unique electronic properties is considered a desirable platform for fabricating electrode/surface interface relationships for constructing asymmetric supercapacitors (ASCs) with high energy density. In this work, a heterostructure based on amorphous nickel boride (Ni_XB) and crystalline square bar-like manganese molybdate (MnMoO₄) was prepared by a simple synthesis strategy. The formation of the Ni_XB/MnMoO₄ hybrid was confirmed by powder X-ray diffraction (p-XRD), field emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), Brunauer-Emmett-Teller (BET), Raman, and X-ray photoelectron spectroscopy (XPS). In this hybrid system (Ni_XB/MnMoO₄), the intact combination of Ni_XB and MnMoO₄ leads to a large surface area with open porous channels and abundant crystalline/amorphous interfaces with a tunable electronic structure. This Ni_XB/MnMoO₄ hybrid shows high specific capacitance (587.4 F g^-1) at 1 A g^-1, and it even retains a capacitance of 442.2 F g^-1 at 10 A g^-1, indicating superior electrochemical performance. The fabricated Ni_XB/MnMoO₄ hybrid electrode also exhibited an excellent capacity retention of 124.4% (10000 cycles) and a Coulombic efficiency of 99.8% at a current density of 10 A g^-1. In addition, the ASC device (Ni_XB/MnMoO₄//activated carbon) achieved a specific capacitance of 104 F g^-1 at 1 A g^-1 and delivered a high energy density of 32.5 Wh.kg^-1 with a power density of 750 W·kg^-1. This exceptional electrochemical behavior is due to the ordered porous architecture and the strong synergistic effect of Ni_XB and MnMoO₄, which enhances the accessibility and adsorption of OH^- ions that improve electron transport. Moreover, the Ni_XB/MnMoO₄//AC device exhibits excellent cyclic stability with a retention of 83.4% of the original capacitance after 10000 cycles, which is due to the heterojunction layer between Ni_XB and MnMoO₄ that can improve the surface wettability without causing structural changes. Our results show that the metal boride/molybdate-based heterostructure is a new category of high-performance and promising material for the growth of advanced energy storage devices.

Synthesis of active-site rich molybdenum-doped manganese tungstate nanocubes for effective electrochemical sensing of the antiviral drug (COVID-19) nitazoxanide

Nitazoxanide (NTZ), a promising antiviral agent, is currently being tested in clinical trials as a potential treatment for novel coronavirus disease 2019 (COVID -19). This paper describes a one-pot hydrothermal synthesis to prepare molybdenum (Mo)-doped manganese tungstate nanocubes (Mo-MnWO4 NCs) for the electrochemical sensing of NTZ. The as-prepared Mo-MnWO4 NCs were characterized using various techniques such as XRD, Raman, FE-SEM, FE-TEM, and XPS to confirm the crystal structure, morphology, and elemental composition. The obtained results demonstrate that Mo doping on MnWO4 generates many vacancy sites, exhibiting remarkable electrochemical activity. The kinetic parameters of the electrode modified with Mo-MnWO4 NCs were calculated to be (Ks) 1.1 × 10-2 cm2 s-1 and (α) 0.97, respectively. Moreover, a novel electrochemical sensor using Mo-MnWO4 NCs was fabricated to detect NTZ, which is used as a primary antibiotic to control COVID-19. Under optimal conditions, the electrochemical reduction of NTZ was determined with a low detection limit of 3.7 nM for a linear range of 0.014-170.2 μM with a high sensitivity of 0.78 μA μM-1 cm-2 and negligible interference with other nitro group-containing drugs, cations, and anions. The electrochemical sensor was successfully used to detect NTZ in the blood serum and urine samples and achieved high recoveries in the range of 94-99.2% and 95.3-99.6%, respectively. This work opens a way to develop high-performance sensing materials by exploring the introduction of defect engineering on metal tungstates to detect drug molecules for practical applications.

Ultrasensitive electrochemical sensor for the detection of carbamazepine based on gadolinium vanadate nanostructure decorated functionalized carbon nanofiber nanocomposite

The gadolinium vanadate nanostructure decorated functionalized carbon nanofiber (GdVO₄/f-CNF) nanocomposite was prepared by the hydrothermal method, which is fabricated on a glassy carbon electrode (GCE) for the determination of carbamazepine (CBZ). The structural morphology of the hydrothermally synthesized GdVO₄/f-CNF material was investigated by several spectroscopy methods such as FESEM, HRTEM, EDS-mapping, XRD, XPS, and Raman. Moreover, the electrical conductivity of our synthesized material was inspected by the electrochemical impedance spectroscopy (EIS) analysis, and the electrochemical performance towards CBZ was inspected by the cyclic voltammetry (CV) and amperometry (AMP) analysis under optimized conditions. The AMP determination of CBZ exhibits the lowest level LOD of 0.0018 μM and a good linear range of 0.01-157 μM. Additionally, our proposed sensor was used to determine the CBZ in the pharmaceutical and, human urine samples which have exposed the acceptable recoveries.

Ni3B as p-Block Element-Modulated Cocatalyst for Efficient Photocatalytic CO2 Reduction

Due to the multiple electron and proton transfer processes involved, the photogenerated charges are easily recombined during the photocatalytic reduction of CO₂, making the generation of the eight-electron product CH₄ kinetically more difficult. Herein, Ni₃B nanoparticles modulated by p-block element were combined with TiO₂ nanosheets to construct a novel Schottky junction photocatalyst (Ni₃B/TiO₂) for the selective photocatalytic conversion of CO₂ to CH₄. The formed Ni₃B/TiO₂ photocatalyst with Schottky junction ensures a transfer pathway of photogenerated electrons from TiO₂ to Ni₃B, which facilitates the accumulation of electrons on the surface of Ni₃B and subsequently improves the activity of photocatalytic CO₂ reduction to CH₄. The optimized Ni₃B/TiO₂ Schottky junction shows an improved CH₄ yield of 30.03 μmol g^-1 h^-1, which was much higher than those of TiO₂ (1.62 μmol g^-1 h^-1), NiO/TiO₂ (2.44 μmol g^-1 h^-1), and Ni/TiO₂ (4.3 μmol g^-1 h^-1). This work demonstrated that the introduction of p-block elements can alleviate the scaling relationship effect of pure metal cocatalysts to a certain extent, and the modified Ni₃B can be used as a promising new cocatalyst to effectively improve the selective photocatalytic of CO₂ to CH₄.

Electrocatalytic nitrate reduction to ammonia via amorphous cobalt boride

Electrocatalytic nitrate reduction reaction (NitRR) is an energy-saving and environmentally benign approach to synthesizing ammonia under ambient conditions. However, the development of noble metal-free catalysts with high activity and selectivity is still a significant challenge. In this study, uniformly dispersed amorphous CoB_x nanoparticles supported on carbon paper were synthesized VIA a simple wet chemical reduction method. As an efficient nitrate reduction electrocatalyst, CoB_x exhibited a maximum faradaic efficiency of 94.00 ± 1.67% and a yield rate of up to 0.787 ± 0.028 mmol h^-1 cm^-2 for ammonia production. The enhanced NitRR performance could be attributed to a partial electron transfer from B to Co, which is necessary for optimizing the adsorption energies of the reaction intermediates and facilitating electron transport. Thus, selective and cost-effective electroreduction of nitrates to ammonia can be achieved using CoB_x nanoparticles.

Element immiscibility assisted Ru@Ni3B as an efficient electrocatalyst toward alkaline and acidic hydrogen evolution reaction

Based on the element immiscibility of Ni-Ru, xRu@Ni₃B (x = 0, 0.2, 0.5, 1.0) were facilely synthesized through a one-step dealloying method. Of them, 1.0Ru@Ni₃B requires overpotentials of 40 ± 0.2 and 72 ± 0.3 mV to reach a current density of -20 mA cm^-2 for acidic and alkaline hydrogen evolution reaction, respectively, which are close to or even better than those of metallic Pt foil. In addition, it could maintain superior catalytic and chemical stability after 24 hours of testing. This work provides a promising strategy for improving the atomic utilization efficiency of highly active noble metals toward the hydrogen evolution reaction (HER).

Electrochemical sensor based on a chitosan-molybdenum vanadate nanocomposite for detection of hydroxychloroquine in biological samples

In this study, we firstly introduce an ultra-high sensitive V_3.6Mo_2.4O₁₆-chitosan (MV-CHT) nanocomposite for electrochemical hydroxychloroquine sulfate (HCQ) monitoring toward paracetamol (PCM) and pantoprazole (PPZ) in environmental and clinical diagnostics. The single-phase MV nanostructures are prepared via the sol-gel pechini route, followed by engineering maleic acid as a structure-directing agent. The stabilization of the MV electro-catalysts is adopted by varying critical factors such as calcination temperature, different chelating ligands, chelating molality and cross-linker concentration. The structural and morphological characterizations, namely, ordered active sites, structural integrity, porous network and dispersibility on the cationic polymer are confirmed by physicochemical analyses. Also, analytical nature of the MV-CHT modified carbon paste electrode (MV-CHT/CPE) is constructed via electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and differential pulse voltammetry (DPV) techniques. As a result, the nano-MV-CHT/CPE platforms with 10% of polymeric matrixes delivered the boosted analytical performance in terms of linear ranges (0.0019-194.0 µM), lower detection limit (LOD = 0.224 nM), together with excellent sensitivity and selectivity. The novel combination of MV nanoparticles and CHT provide the fluent channels for rapid charge transport and effective surface area. Such results illustrate the synergistic and interaction capability of MV-CHT-based sensing catalysts with bioactive molecules, which make them as superior drug monitoring devices.

Unprecedented 2D GNR-CoB nanocomposite for detection and degradation of malachite green - A computational prediction of degradation pathway and toxicity

In the present work, we have synthesized a novel 2D GNR-CoB composite and was applied it for electrochemical sensing and photocatalytic degradation of the malachite green (MG). The physicochemical properties of the 2D GNR-CoB were analyzed using X-ray diffraction, Transmission electron microscopy, Energy dispersive X-ray diffraction which depicts the morphological and crystalline nature of the prepared composite. The pencil graphite electrode modified with 2D GNR-CoB composite showed excellent electrochemical response for MG detection with a LOD of 1.92 nM, linear range of 25-350 nM with a high sensitivity of 1.714 μA μM^-1 cm^-2. Besides, the 2D GNR-CoB modified PGE exhibited good recovery for the detection of MG in real samples such as green peas and lady's fingers. Furthermore, the 2D GNR-CoB modified electrode showed excellent photocatalytic activity for the degradation of MG. It suggests that under visible light, GNR-CoB material generates superoxide (·O₂^-) and hydroxyl (·OH) radicals for MG degradation. The prepared composite showed an efficiency of 91.28% towards the degradation of MG. Based on the experimental analysis and density functional theory calculations, a photocatalytic degradation mechanism pathway for MG is proposed. A quantitative structure-activity relationship study was used to examine the toxicity of the degradation intermediates.

Manipulation on Two-Dimensional Amorphous Nanomaterials for Enhanced Electrochemical Energy Storage and Conversion

Low-carbon society is calling for advanced electrochemical energy storage and conversion systems and techniques, in which functional electrode materials are a core factor. As a new member of the material family, two-dimensional amorphous nanomaterials (2D ANMs) are booming gradually and show promising application prospects in electrochemical fields for extended specific surface area, abundant active sites, tunable electron states, and faster ion transport capacity. Specifically, their flexible structures provide significant adjustment room that allows readily and desirable modification. Recent advances have witnessed omnifarious manipulation means on 2D ANMs for enhanced electrochemical performance. Here, this review is devoted to collecting and summarizing the manipulation strategies of 2D ANMs in terms of component interaction and geometric configuration design, expecting to promote the controllable development of such a new class of nanomaterial. Our view covers the 2D ANMs applied in electrochemical fields, including battery, supercapacitor, and electrocatalysis, meanwhile we also clarify the relationship between manipulation manner and beneficial effect on electrochemical properties. Finally, we conclude the review with our personal insights and provide an outlook for more effective manipulation ways on functional and practical 2D ANMs.