Unleashing unprecedented activation of high-valent Ni and Fe charge dynamics in CeF3-NiFe layered double hydroxide heterostructure: Demonstrating oxygen evolution reaction at an extremely high current density.

The efficacy of any electrochemical reaction hinges on the extent of interaction achievable between reactive intermediates and the electrocatalytic active site. Any weak adsorption of these intermediates on the metal's active site results in low oxygen evolution reaction (OER) rates, mainly when catalysed by the Ni-based layered double hydroxide. To tackle this challenge, a heterojunction consisting of nickel-iron layered double hydroxide (NiFe-LDH) and cerium trifluoride (CeF3) is synthesized. Both phases were developed in-situ to have an abundance of heterointerfaces. The charge transfer amid the NiFe-LDH and CeF3 phases is brought about via these heterointerfaces. As a result, the overall charge dynamics associated with nickel (Ni) and iron (Fe) atoms are somewhat increased, and an enhanced positive charge on the metal site makes it more active in grabbing the reactive species, thereby making the entire OER process faster. The CeF3-NiFeLDH catalyst reaches a current density of 1000 mA cm-2 at an overpotential of 340 mV. Such a high current density is highly significant for the industrial-scale production of the products. The catalyst demonstrated impressive durability, maintaining stable performance for 90 h while operating at 500 mA cm-2. The charge dynamics between both phases were thoroughly examined using X-ray photoelectron spectroscopy (XPS).

Electronic redistribution through the interface of MnCo2O4-Ni3N nano-urchins prompts rapid In situ phase transformation for enhanced oxygen evolution reaction.

One of the most coveted objectives in the realm of energy conversion technologies is the development of highly efficient and economically viable electrocatalysts for the oxygen evolution reaction. The commercialization of such techniques has thus far been impeded by their slow response kinetics. One of the many ways to develop highly effective electrocatalysts is to judiciously choose a coupling interface that maximizes catalyst performance. In this study, the in situ electrochemical phase transformation of MnCo2O4-Ni3N into MnCo2O4-NiOOH is described. The catalyst has an exceptional overpotential of 224 mV to drive a current density of 10 mA cm-2. Strong interfacial contact is seen in the MnCo2O4-Ni3N catalyst, leading to a considerable electronic redistribution between the MnCo2O4 and Ni3N phases. This causes an increase in the valence state of Ni, which makes it an active site for the adsorption of *OH, O*, and *OOH (intermediates). This charge transfer facilitates the rapid phase transformation to form NiOOH from Ni3N. At a higher current density of 300 mA cm-2, the catalyst remained stable for a period of 140 h. DFT studies also revealed that the in situ-formed NiOOH on the MnCo2O4 surface results in superior OER kinetics compared to that of NiOOH alone.

Synergistic modulation in a triphasic Ni5P4-Ni2P@Ni3S2 system manifests remarkable overall water splitting.

The potential for water splitting electrocatalysts with high efficiency paves the way for a sustainable future in hydrogen energy. However, this task is challenging due to the sluggish kinetics of the oxygen evolution reaction (OER), which has a significant impact on the hydrogen evolution reaction (HER). Herein multi-heterointerface of Ni5P4-Ni2P@Ni3S2 was fabricated by a two-step synthesis procedure that consist the development of Ni5P4-Ni2P nanosheets over nickel foam followed by the electrodeposition of Ni3S2. The HR-TEM analysis shows that the Ni5P4-Ni2P@Ni3S2 nanosheets array provide numerous well-exposed diverse heterointerfaces. The electrochemical investigations conducted on the Ni5P4-Ni2P@Ni3S2 nanosheets for complete water splitting indicate that they possess an overpotential of 73 mV and 230 mV in HER and OER respectively, enabling them to generate a current density of 10 and 50 mA cm-2. The nanosheets also demonstrate Tafel slope values of 95 mV dec-1 and 83 mV dec-1 for HER and OER, respectively. The HER stability of the catalyst was conducted for 45 h using chronoamperometric technique under a current density of 20 mA cm-1, while the stability test for OER was carried out at current densities of 100 and 200 mA cm-1 for 100 h each. Furthermore, in the overall water splitting, the catalyst exhibits a cell voltage of 1.47 V@10 mA cm-2 and displayed a stability operation for 100 h at a current density of 150 mA cm-1.

Electronic redistribution over the active sites of NiWO4-NiO induces collegial enhancement in hydrogen evolution reaction in alkaline medium.

The activity-enhancement of a new-generation catalyst focuses on the collegial approach among specific solids which exploit the mutual coactions of these materials for HER applications. Strategic manipulation of these solid interfaces typically reveals unique electronic states different from their pure phases, thus, providing a potential passage to create catalysts with excellent activity and stability. Herein, the formation of the NiWO4-NiO interface has been designed and synthesized via a three-step method. This strategy enhances the chance of the formation of abundant heterointerfaces due to the fine distribution of NiWO4 nanoparticles over Ni(OH)2 sheets. NiWO4-NiO has superior HER activity in an alkaline (1 M KOH) electrolyte with modest overpotentials of 68 mV at 10 mA cm-2 current density. The catalyst is highly stable in an alkaline medium and negligible change was observed in the current density even after 100 h of continuous operation. This study explores a unique method for high-performance hydrogen generation by constructing transition metal-oxides heterojunction. The XPS studies reveal an electronic redistribution driven by charge transfer through the NiWO4-NiO interface. The density functional theory (DFT) calculations show that the NiWO4-NiO exhibits a Pt-like activity with the hydrogen Gibbs free energy (ΔGH*) value of 0.06 eV compared to the Pt(ΔGH* = -0.02 eV).

Interfacial interaction induced OER activity of MOF derived superhydrophilic Co3O4-NiO hybrid nanostructures.

Electrocatalytic water splitting is one of the key technologies for future energy systems envisioned for the storage of energy obtained from variable renewables and green fuels. The development of efficient, durable, Earth-abundant and cheap electrocatalysts for the oxygen evolution reaction is a scorching area of research. The oxygen evolution reaction has huge potential for fuel cell and metal-air battery applications. Herein, we reported interfacially interacted and uniformly decorated Co3O4-NiO hybrid nanostructures formed by a metal-organic framework (Co2-BDC(OH)2) using BDC as a linker to the metal center. The fine nanosheets of Co2-BDC(OH)2 were first uniformly grown over the honeycomb-like structure of nickel foam (NF). After controlled calcination of these nanosheets/NF composites, a uniformly decorated, binder-free Co3O4-NiO/NF electrocatalyst was synthesized. The transformation of Co2-BDC(OH)2/NF into Co3O4-NiO/NF was characterized by several techniques such as powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy, transmission electron microscopy, etc. The catalyst exhibits a low overpotential of 311 mV vs. RHE at 10 mA cm-2 current density. The catalyst also shows long-term stability (24 h) with a Tafel slope value of 90 mV dec-1. The obtained experimental results are also in-line with the theoretical data acquired from model systems.

Unraveling a Graphene Exfoliation Technique Analogy in the Making of Ultrathin Nickel-Iron Oxyhydroxides@Nickel Foam to Promote the OER.

One of the major objectives of using the improved Hummers' method was to exfoliate the graphene layers by oxidizing and thereafter reducing them to obtain highly conductive reduced graphene layers, which can be used in the construction of electronic devices or as a part of catalyst composites in energy conversion reactions. Herein, we have employed a similar idea to exfoliate the layered double hydroxide (LDH), which is proposed as a promising material for the oxygen evolution reaction (OER) electrocatalysis. Usually, the efficiency of these materials is largely restricted due to their sheetlike morphology, which is susceptible to stacking. In this work, NiFe-LDH sheets were fabricated on nickel foam in a one-step co-precipitation technique and their ultrathin nanosheets (∼2 nm) are obtained by in situ oxygen-plasma-controlled exfoliation. In addition, the oxygen vacancies in exfoliated sheets were generated by a chemical reduction method that further improved the electronic conductivity and overall electrocatalytic performance of the catalyst. This approach can address the limitations of NiFe-LDH, such as poor conductivity and low stability, making it more efficient for electrocatalysis. It is also observed that the catalyst having 60 s O-plasma exposure after chemical reduction, i.e., NiFe-OOHOV, outperformed remaining electrocatalysts and exhibited superior OER activity with a low overpotential of 330 mV to achieve a high current density of 50 mA cm-2. The catalyst also displayed an ECSA-normalized OER overpotential of 288 mV at a current density of 10 mA cm-2 and exhibited excellent long-term stability (120 h) in an alkaline electrolyte. Remarkably, ultrathin defect-rich catalyst continuously produced O2, resulting in a high faradaic efficiency of 98.1% for the OER.

Is the Electrophilicity of the Metal Nitrene the Sole Predictor of Metal-Mediated Nitrene Transfer to Olefins? Secondary Contributing Factors as Revealed by a Library of High-Spin Co(II) Reagents.

Recent research has highlighted the key role played by the electron affinity of the active metal-nitrene/imido oxidant as the driving force in nitrene additions to olefins to afford valuable aziridines. The present work showcases a library of Co(II) reagents that, unlike the previously examined Mn(II) and Fe(II) analogues, demonstrate reactivity trends in olefin aziridinations that cannot be solely explained by the electron affinity criterion. A family of Co(II) catalysts (17 members) has been synthesized with the assistance of a trisphenylamido-amine scaffold decorated by various alkyl, aryl, and acyl groups attached to the equatorial amidos. Single-crystal X-ray diffraction analysis, cyclic voltammetry and EPR data reveal that the high-spin Co(II) sites (S = 3/2) feature a minimal [N3N] coordination and span a range of 1.4 V in redox potentials. Surprisingly, the Co(II)-mediated aziridination of styrene demonstrates reactivity patterns that deviate from those anticipated by the relevant electrophilicities of the putative metal nitrenes. The representative L4Co catalyst (-COCMe3 arm) is operating faster than the L8Co analogue (-COCF3 arm), in spite of diminished metal-nitrene electrophilicity. Mechanistic data (Hammett plots, KIE, stereocontrol studies) reveal that although both reagents follow a two-step reactivity path (turnover-limiting metal-nitrene addition to the C b atom of styrene, followed by product-determining ring-closure), the L4Co catalyst is associated with lower energy barriers in both steps. DFT calculations indicate that the putative [L4Co]NTs and [L8Co]NTs species are electronically distinct, inasmuch as the former exhibits a single-electron oxidized ligand arm. In addition, DFT calculations suggest that including London dispersion corrections for L4Co (due to the polarizability of the tert-Bu substituent) can provide significant stabilization of the turnover-limiting transition state. This study highlights how small ligand modifications can generate stereoelectronic variants that in certain cases are even capable of overriding the preponderance of the metal-nitrene electrophilicity as a driving force.

Strong Interactions between the Nanointerfaces of Silica-Supported Mo2C/MoP Heterojunction Promote Hydrogen Evolution Reaction.

Hydrogen is one of the cleanest forms of energy carrier which can solve the twin problem of exhaustion of fossil fuels and climate change. The exploration of low-cost and earth-abundant electrocatalysts for hydrogen generation process is an emerging area of research. Profound catalyst tailoring with mutually contrast phases on a porous support for crafting large hydrogen evolution reaction (HER) active sites increases the catalytic activity in many folds. Herein, a porous silica-supported molybdenum phosphide and molybdenum carbide nanoparticle (SiMoCP) has been synthesized. The intermingled porous molybdenum carbide and molybdenum phosphide nanohybrid shows excellent catalytic activity toward hydrogen evolution. Such a modified nanostructured electrocatalyst enhances the electrode-electrolyte interaction and suppresses the charge transfer resistance. As a result, the electrocatalyst (SiMoCP) accomplishes very high HER activity with an onset potential of 53 mV and an overpotential of 88 mV at a current density of 10 mA cm-2 in the acidic medium. Furthermore, the SiMoCP catalyst showed a Tafel slope value of 37 mV dec-1 with long-term durability of 5000 cycles.

Uniformly Decorated Molybdenum Carbide/Nitride Nanostructures on Biomass Templates for Hydrogen Evolution Reaction Applications.

Natural fibrils derived from biomass were used as a template to synthesize uniformly decorated nanoparticles (10-12 nm) of molybdenum carbide (Mo2C) and molybdenum nitride (Mo2N) supported on carbon. The nanoparticles have been synthesized through the carburization and nitridation of molybdenum on cotton fibrils, using a high-temperature solid-state reaction. The catalyst exhibits an onset potential of 110 mV and an overpotential of 167 mV to derive a cathodic current density of 10 mA cm-2. The electrocatalyst also demonstrates excellent long-term durability of more than 2500 cycles in acidic media with a Tafel slope value of 62 mV dec-1.

Hydrated FePO4 nanoparticles supported on P-doped RGO show enhanced ORR activity compared to their dehydrated form in an alkaline medium.

One-step hydrothermal growth of FePO4 nanoparticles (15-25 nm) uniformly decorated on the P-doped reduced graphene oxide (PRGO) was studied for oxygen reduction reaction (ORR) activity. The role of lattice water in the enhancement of catalytic activity in the hydrated FePO4·2H2O with respect to its dehydrated form in the alkaline medium was contested. The hydrodynamic LSV at 1600 rpm in alkaline medium (0.1 M KOH electrolyte) indicates an increase in the cathodic current density of the PRGO supported FePO4·2H2O catalyst, which reaches as high as 5.8 mA cm-2, close to the best known commercially available Pt/C catalyst. The stability in terms of retention of activity after 22 000 s with the hydrated form was found to be 90.7% which is 26.7% higher than that of the dehydrated form.

Environmentally Benign Metal-Free Reduction of GO Using Molecular Hydrogen: A Mechanistic Insight.

A simple yet effective methodology to obtain high-quality reduced graphene oxide (RGO) using a tetrahydrofuran suspension of GO under hydrogen at moderate pressure has been demonstrated. The extent of reduction as a function of the pressure of hydrogen gas, temperature, and time was studied, where the abstraction of oxygen is achievable with least mutilation of C-sp2 bonds, hence upholding the integrity of the graphene sheet. Herein, the formation of a short-lived species is proposed, which is possibly responsible for such reduction. A detailed theoretical calculation along with in situ UV-visible experiments reveals the existence of a transient solvated electron species in the reaction medium. The hydrogen RGO (HRGO) achieved a C/O atomic ratio of 11.3. The conductivity measurements show that HRGO reached as high as 934 S/m, which indicates a high quality of RGO. The process is hassle-free, environmentally benign, and can be scaled up effortlessly without compromising the quality of the material.

A versatile tripodal Cu(I) reagent for C-N bond construction via nitrene-transfer chemistry: catalytic perspectives and mechanistic insights on C-H aminations/amidinations and olefin aziridinations.

A Cu(I) catalyst (1), supported by a framework of strongly basic guanidinato moieties, mediates nitrene-transfer from PhI═NR sources to a wide variety of aliphatic hydrocarbons (C-H amination or amidination in the presence of nitriles) and olefins (aziridination). Product profiles are consistent with a stepwise rather than concerted C-N bond formation. Mechanistic investigations with the aid of Hammett plots, kinetic isotope effects, labeled stereochemical probes, and radical traps and clocks allow us to conclude that carboradical intermediates play a major role and are generated by hydrogen-atom abstraction from substrate C-H bonds or initial nitrene-addition to one of the olefinic carbons. Subsequent processes include solvent-caged radical recombination to afford the major amination and aziridination products but also one-electron oxidation of diffusively free carboradicals to generate amidination products due to carbocation participation. Analyses of metal- and ligand-centered events by variable temperature electrospray mass spectrometry, cyclic voltammetry, and electron paramagnetic resonance spectroscopy, coupled with computational studies, indicate that an active, but still elusive, copper-nitrene (S = 1) intermediate initially abstracts a hydrogen atom from, or adds nitrene to, C-H and C═C bonds, respectively, followed by a spin flip and radical rebound to afford intra- and intermolecular C-N containing products.

Synthesis and characterization of copper(II) and zinc(II)-based potential chemotherapeutic compounds: their biological evaluation viz. DNA binding profile, cleavage and antimicrobial activity.

Metal-based cancer chemotherapeutic agents of the type [Cu(phen)TzCl(2)]H(2)O 1 and [Zn(phen)(Tz)Cl(2)·H(2)O] 2, where phen = 1,10-phenanthroline and Tz = 1,2,4-triazole have been synthesized and characterized by various spectroscopic and analytical techniques. The structure of complex 1 was also determined by X-ray crystallography. The in vitro DNA binding studies of complexes 1 and 2 with CT DNA were carried out by various biophysical and molecular docking techniques. Both the complexes cleave supercoiled pBR322 DNA via hydrolytic pathway, as validated by T4 DNA ligase assay. Furthermore, both complexes exhibited significant antimicrobial activity. The results revealed that complex 1 has better prospectus to act as cancer chemotherapeutic candidate which warrants further in vitro and in vivo anticancer investigations.

Molecular drug design, synthesis and structure elucidation of a new specific target peptide based metallo drug for cancer chemotherapy as topoisomerase I inhibitor.

To evaluate the biological preference of metallopeptide drugs in cancer cells, a new dinuclear copper(II) complex [Cu(2)(glygly)(2)(ppz)(H(2)O)(4)]·2H(2)O (1) (glygly = glycyl glycine anion and ppz = piperazine), was designed and synthesized as topoisomerase I inhibitor. The structural elucidation of the complex was done by elemental analysis, spectroscopic methods and single crystal X-ray diffraction. The in vitro DNA binding studies of complex 1 with CT DNA were carried out by employing different optical methods viz. UV-vis, fluorescence and circular dichroism. The molecular docking technique was also utilized to ascertain the mechanism and mode of action towards the molecular target DNA and enzymes. Complex 1 cleaves pBR322 DNA via an oxidative mechanism and strongly binds to the DNA minor groove. Furthermore, complex 1 exhibits significant inhibitory effects on the catalytic activity of topoisomerase I at a very low concentration, ~12.5 µM, in addition to its excellent SOD mimics (IC(50)~0.086 µM).

Synthesis and antiinflammatory activity of some new 1,3,5-trisubstituted pyrazolines bearing benzene sulfonamide.

Nineteen new 2-pyrazoline bearing benzenesulfonamide derivatives were synthesized by condensing chalcones with 4-hydrazinonbenzenesulfonamide hydrochloride. Their chemical structures were proved by means of IR, (1)H NMR, (13)C NMR, mass spectroscopic and elemental analyses data. These compounds were tested at dose of 20mg/kg for their anti-inflammatory activity in carrageenan-induced rat paw edema model and volume of paw edema was measured at 0, 3 and 5h. Two compounds 3k and 3l were found to be more active than celecoxib throughout the study (at 3 and 5h). While two other compounds 3m and 3n showed more potent activity than celecoxib at 5h. They are devoid of ulcerogenic potential when administered orally at a dose of 60 mg/kg. Compounds (3k-m) showed COX-1 and COX-2 inhibitory activity at 0.05 microM.

Chlorido{5-chloro-2-[2-(methyl-sulfanyl)phenyl-diazen-yl]phenyl}-platinum(II).

The title compound, [Pt(C(13)H(10)ClN(2)S)Cl], contains a Pt atom tetra-coordinated by a benzene C, a diazene N, a Cl and an S atom in an approximately square-planar geometry. The mol-ecules dimerize through a nonbonded S⋯S inter-action [S⋯S = 3.523 (18) Å]. There are no hydrogen bonds and the crystal packing is stabilized by four inter-molecular π-π inter-actions; the centroid-centroid distances are 3.804 (3), 3.638 (3), 3.804 (3) and 3.638 (3) Å, and the corresponding perpendicular distances are 3.369, 3.448, 3.406 and 3.466 Å.