Lewis acidic Fe3+-driven catalytic active Ni3+ formation in Fe-free metal-organic framework for enhanced electrochemical glucose sensing

Manipulating metal valence states and porosity in the metal-organic framework (MOF) by alloying has been a unique tool for creating high-valent metal sites and pore environments in a structure that are inaccessible by other methods, favorable for accelerating the catalytic activity towards sensing applications. Herein, we report Fe3+-driven formation of catalytic active Ni3+ species in the amine-crafted benzene-dicarboxylate (BDC-NH2)-based MOF as a high-performance electrocatalyst for glucose sensing. This work took the benefit of different bonding stability between BDC-NH2 ligand, and Fe3+ and Ni2+ metal precursor ions in the heterometallic NixFe(1-x)-BDC-NH2 MOF. The FeCl3 that interacts weakly with ligand, oxidizes the Ni2+ precursor to Ni3+-based MOF owing to its Lewis acidic behavior and was subsequently removed from the structure supported by Ni atoms, during solvothermal synthesis. This enables to create mesopores within a highly stable Ni-MOF structure with optimal feed composition of Ni0.7Fe0.3-BDC-NH2. The Ni3+-based Ni0.7Fe0.3-BDC-NH2 demonstrates superior catalytic properties towards glucose sensing with a high sensitivity of 13,435 µA mM-1 cm-2 compared to the parent Ni2+-based Ni-BDC-NH2 (10897 μA mM-1cm-2), along with low detection limit (0.9 μM), short response time (≤5 s), excellent selectivity, and higher stability. This presented approach for fabricating high-valent nickel species, with a controlled quantity of Fe3+ integrated into the structure allowing pore engineering of MOFs, opens new avenues for designing high-performing MOF catalysts with porous framework for sensing applications.

Partial Oxidation of Bio-methane over Nickel Supported on MgO-ZrO2 Solid Solutions

Syngas can be produced from biomethane via Partial Oxidation of Methane (POM), being an attractive route since it is ecofriendly and sustainable. In this work, catalysts of Ni supported on MgO-ZrO2 solid solutions, prepared by a one-step polymerization method, were characterized by HRTEM/EDX, XRD, XPS, H2-TPR, and in situ XRD. All catalysts, including Ni/ZrO2 and Ni/MgO as reference, were tested for POM (CH4:O2 molar ratio 2, 750 ºC, 1 atm). NiO/MgO/ZrO2 contained two solid-solutions, MgO-ZrO2 and NiO-MgO, as revealed by XRD and XPS. Ni (30 wt%) supported on MgO-ZrO2 solid solution exhibited high methane conversion and hydrogen selectivity. However, depending on the MgO amount (0, 4, 20, 40, 100 molar percent) major differences in NiO reducibility, growth of Ni0 crystallite size during H2 reduction and POM, and in carbon deposition rates were observed. Interestingly, catalysts with lower MgO content achieved the highest CH4 conversion (~ 95%), high selectivity to H2 (1.7) and CO (0.8), and low carbon deposition rates (0.024 g carbon.gcat-1 h-1) with Ni4MgZr (4 mol% MgO) turning out to be the best catalyst. In situ XRD during POM indicated metallic Ni nanoparticles (average crystallite size of 31 nm), supported by MgO-ZrO2 solid solution, with small amounts of NiO-MgO being present as well. The presence of MgO also influenced the morphology of the carbon deposits, leading to filaments instead of amorphous carbon. A combustion-reforming mechanism is suggested and using a MgO-ZrO2 solid solution support strongly improves catalytic performance, which is attributed to effective O2, CO2 and H2O activation at the Ni/MgO-ZrO2 interface.

Environmental benefits from the use of CO2 in the thermal disposal of cigarette butts

As the global consumption of cigarettes has increased, the massive generation of cigarette butts (CBs) has led to critical environmental and health problems. Landfilling or incineration of CBs has been conventionally carried out, but such disposal protocols have suffered from the potential risks of the unwanted/uncontrolled release of leachates, carcinogens, and toxic chemicals into all environmental media. Thus, this study focuses on developing an environmentally dependable method for CB disposal. Littered CBs from filtered/electronic cigarettes were valorized into syngas (H₂/CO). To seek a greener approach for the valorization of CBs, CO₂ was intentionally considered as a reaction intermediate. Prior to multiple pyrolysis studies, the toxic chemicals in the CBs were qualitatively determined. This study experimentally proved that the toxic chemicals in CBs were detoxified/valorized into syngas. Furthermore, this work demonstrated that CO₂ was effective in thermally destroying toxic chemicals in CBs via a gas-phase reaction. The reaction features and CO₂ synergistically enhance syngas production. With the use of a supported Ni catalyst and CO₂, syngas production from the catalytic pyrolysis of CBs was greatly enhanced (approximately 4 times). Finally, the gas-phase reaction by CO₂ was reliably maintained owing to the synergistic mechanistic/reaction feature of CO₂ for coke formation prevention on the catalyst surface.

One-Step Solvothermal Synthesis of Ni Nanoparticle Catalysts Embedded in ZrO2 Porous Spheres to Suppress Carbon Deposition in Low-Temperature Dry Reforming of Methane

Ni nanoparticle catalysts embedded in ZrO₂ porous spheres and ZrO₂ porous composite spheres, SiO₂-ZrO₂, MgO-ZrO₂, and Y₂O₃-ZrO₂, with 83-115 nm diameter and 167-269 m²/g specific surface area were prepared by a one-pot and one-step solvothermal reaction from precursor solutions consisting of Ni(NO₃)₂‧6H₂O, Zr(OⁿBu)₄, and acetylacetone in moist ethanol combined with either Si(OEt)₄, magnesium acetylacetate, or Y(OⁱPr)₃. The obtained Ni catalysts have high specific surface areas of 130-196 m²/g, even after high-temperature reduction by H₂ at 450 °C for 2 h. They were utilized as catalysts for low-temperature dry reforming of methane (DRM) at 550 °C to suppress carbon deposition on Ni nanoparticles. The Ni catalysts embedded in SiO₂-ZrO₂ and Y₂O₃-ZrO₂ demonstrated high catalytic activity and long stability in the reaction. Moreover, carbon deposition on Ni nanoparticles in the DRM reaction was effectively suppressed in when using the SiO₂-ZrO₂ and Y₂O₃-ZrO₂ composites.

Facile fabrication of GCE/Nafion/Ni composite, a robust platform to detect hydrogen peroxide in basic medium via oxidation reaction

Nickel particles alone can oxidize hydrogen peroxide but confronts extreme stability problem which imparts a barrier to act as sensor. The porous Nafion bed on glassy carbon electrode (GCE) surface provides the sureness of incorporating of Ni particles which was further exploited as an electrochemical sensor for H₂O₂ detection through oxidative degradation process. The simple electrochemical incorporation of Ni particles along the pores of Nafion improves the stability of the sensor significantly. The oxidative pathway of hydrogen peroxide on GCE/Nafion/Ni was probed by analyzing mass transfer dependent linear sweep voltammograms both in static and rotating modes along with chronoamperometry. An electron transfer step determines the overall reaction rate with k°= 2.72 × 10^-4 cm s^-1, which is supported by the values of transfer coefficient (β) in between (0.68-0.75). Sensing performance was evaluated by recording differential pulse voltammograms (DPVs) with the linear detection limit (LOD) of 1.8 μM and linear dynamic range (LDR) of 5-500 μM. Real samples from industrial sources were successfully quantified with excellent reproducibility mark GCE/Nafion/Ni electrode as an applicable sensor.

Nickel Catalysts Supported on Acetylene Black for High-Efficient Electrochemical Oxidation and Sensitive Detection of Glucose

Electrocatalytic glucose oxidation is a very important reaction in glucose fuel cell and medical diagnosis, which is limited by sluggish reaction kinetics and low diffusion coefficient. Herein, a composite (donated as Ni₆/AB) consisting of atomically precise nickel catalyst with defined crystal structure [Ni₆(SC₁₂H₂₅)₁₂] and acetylene black(AB) has been initiated as a novel and high-efficient non-noble metal catalyst for the electrochemical oxidation of glucose benefiting from its high exposure of active sites and increased electron/mass transport. The present Ni₆/AB composites display the onset potential of +1.24 V and the maximum current density of 5 mA cm^-2 at the potential of +1.47 V in the electrolyte of 0.1 M KOH with 5 mM glucose. This electrochemical performance is much superior to the alone nickel catalysts, acetylene black, and previous reported nanomaterials. Furthermore, the obtained Ni₆/AB composites are also expected to find important application in the electrochemical detection of glucose due to its high electrochemical performance. The sensitivity and the detection of limit are determined to be 0.7709 mA cm^-2 mM^-1 and 1.9 μM, respectively. Our study demonstrates that atomically precise nickel catalysts on acetylene black could be potential promising materials for next-generation energy devices and electrochemical sensors.

Synthesis of silicon-functionalized polyolefins by subsequent cobalt-catalyzed dehydrogenative silylation and nickel-catalyzed copolymerization

Metal catalyzed olefin hydrosilylation and metal mediated olefin polymerization are both of great academic and industrial importance. In this article, these two aspects are combined to prepare silicon-functionalized polyolefin materials. First, pyridine-diimine cobalt-catalyzed dehydrogenative silylations of various terminal olefins with alkylsilanes lead to the formation of a variety of allylsilanes at high yields. Then, the allylsilanes are copolymerized with ethylene using an α-diimine nickel catalyst, leading to the formation of branched polyolefins with high molecular weight and moderate comonomer incorporation. This subsequent catalytic process is an efficient strategy for the synthesis of silicon-functionalized polyolefins using widely available and inexpensive starting materials.

Nickel-Catalyzed Cross-Coupling Reactions of Unreactive Phenolic Electrophiles via C-O Bond Activation

Nickel-catalyzed cross-coupling reactions of aryl esters, carbamates, carbonates, ethers and arenols are reviewed. Carbon-oxygen bonds in these phenol derivatives cannot be activated by palladium, a typical cross-coupling catalyst, but a low valent nickel species in conjunction with a strong σ-donor ligand is uniquely effective for achieving this. The review is organized primarily by substrate class and secondarily by coupling partners, encompassing organometallics, heteroatom nucleophiles, C-H bonds and many others. Although the reactions in this category are covered thoroughly, each reaction is described only briefly, so that it is possible to quickly overview the spectrum of nickel-catalyzed cross-coupling reactions of inert phenol derivatives. The robustness of inert phenol derivatives under typically used catalytic conditions as well as their utility as a directing group allow unique synthetic applications of these new C-O cross-coupling reactions, which is also included in cases where appropriate. Mechanistic aspects of C-O bond activation by nickel are also summarized, highlighting their diversity compared with the C-X bond activation involved in conventional cross-coupling processes.

Pulsed laser deposition of single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 core/shell nanowires

Single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 (CI/CIGS) core/shell nanowires are fabricated by pulsed laser deposition with Ni nanoparticles as catalyst. The CI/CIGS core/shell nanowires are made up of single-crystalline CI cores surrounded by single-crystalline CIGS shells. The CI/CIGS nanowires are grown at a considerably low temperature (350°C ~ 450°C) by vapor-liquid-solid mode combined with vapor-solid mode. The distribution density of the nanowires increases with the increasing of the deposition duration, and the substrate temperature determines the lengths of the nanowires. The U-V absorption spectra of the CIGS thin films with and without the CI/CIGS core/shell nanowires demonstrate that the CI/CIGS nanowires can remarkably enhance the absorption of CIGS thin films in the spectrum range of 300 to 900 nm.

PACS

61.46. + w; 61.41.e; 81.15.Fg; 81.07.b.