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Abstract: Keggin‐type polyoxometalate anions [XM12O40]n− are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW12O40]6− turns into an efficient and robust electrocatalyst upon its confinement in the well‐defined void space of ZIF‐8, a metal–organic framework (MOF). [H6CoW12O40]@ZIF‐8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O2(mol Co)−1 s−1, one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in this electrocatalyic water oxidation. [ABSTRACT FROM AUTHOR]

Abstract: Keggin‐type polyoxometalate anions [XM12O40]n− are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW12O40]6− turns into an efficient and robust electrocatalyst upon its confinement in the well‐defined void space of ZIF‐8, a metal–organic framework (MOF). [H6CoW12O40]@ZIF‐8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O2(mol Co)−1 s−1, one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in this electrocatalyic water oxidation. [ABSTRACT FROM AUTHOR]

The design and synthesis of an efficient and robust water-oxidation catalyst with inexpensive materials remains an important challenge in the context of artificial photosynthesis. Herein, a simple but unique technique is reported to in situ generate a thin-film of α-Co(OH)2 on the surface of zeolite-Y [hereafter referred to as Y-α-Co(OH)2] that acts as an efficient and stable catalyst for electrochemical water oxidation in alkaline medium. Catalyst Y-α-Co(OH)2 is so stable that it retains its catalytic activity even after 2000 cyclic voltammetric cycles of water oxidation. Expectedly, the chemical composition of α-Co(OH)2 on the surface of zeolite-Y remains same as that of parent Y-α-Co(OH)2 after 2000 electrocatalytic cycles. A Tafel slope as low as 59 mV decade−1 in 0.1 m KOH (pH 13) suggests faster oxygen evolution kinetics (overpotential=329 mV; turnover frequency=0.35 mol O2 (mol Co)−1 s−1 at 1 mA cm−2) than the existing α-Co(OH)2-based electrocatalysts operating in alkaline medium. [ABSTRACT FROM AUTHOR]

Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal-organic hybrid compound [{Co3(μ3-OH)(BTB)2(dpe)2} {Co(H2O)4(DMF)2}0.5]n⋅ n H2O ( Co-WOC-1) as an effective and stable water-oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co-WOC-1, a mononuclear CoII complex {Co(H2O)4(DMF)2}2+ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s−1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host-guest system can be described as a 'ship-in-a-bottle', and is a new class of heterogeneous WOC. [ABSTRACT FROM AUTHOR]

Preparing efficient and robust water oxidation catalyst (WOC) with inexpensive materials remains a crucial challenge in artificial photosynthesis and for renewable energy. Existing heterogeneous WOCs are mostly metal oxides/hydroxides immobilized on solid supports. Herein we report a newly synthesized and structurally characterized metal-organic hybrid compound [{Co3(μ3-OH)(BTB)2(dpe)2} {Co(H2O)4(DMF)2}0.5]n⋅ n H2O ( Co-WOC-1) as an effective and stable water-oxidation electrocatalyst in an alkaline medium. In the crystal structure of Co-WOC-1, a mononuclear CoII complex {Co(H2O)4(DMF)2}2+ is encapsulated in the void space of a 3D framework structure and this translationally rigid complex cation is responsible for a remarkable electrocatalytic WO activity, with a catalytic turnover frequency (TOF) of 0.05 s−1 at an overpotential of 390 mV (vs. NHE) in 0.1 m KOH along with prolonged stability. This host-guest system can be described as a 'ship-in-a-bottle', and is a new class of heterogeneous WOC. [ABSTRACT FROM AUTHOR]

Water splitting, leading to hydrogen and oxygen in a process that mimics natural photosynthesis, is extremely important for devising a sustainable solar energy conversion system. Development of earth-abundant, transition metal-based catalysts that mimic the oxygen-evolving complex of photosystem II, which is involved in oxidation of water to O2 during natural photosynthesis, represents a major challenge. Further, understanding the exact mechanism, including elucidation of the role of active metal-oxo intermediates during water oxidation (WO), is critical to the development of more efficient catalysts. Herein, we report FeIII complexes of biuretmodified tetra-amidomacrocyclic ligands (Fe-TAML; 1a and 1b) that catalyze fast, homogeneous, photochemical WO to give O2, with moderate efficiency (maximum TON = 220, TOF = 0.76 s-1). Previous studies on photochemical WO using iron complexes resulted in demetalation of the iron complexes with concomitant formation of iron oxide nanoparticles (NPs) that were responsible for WO. Herein, we show for the first time that a high valent FeVM (O) intermediate species is photochemically generated as the active intermediate for the oxidation of water to O2. To the best of our knowledge, this represents the first example of a molecular iron complex catalyzing photochemical WO through a FeV(O) intermediate. [ABSTRACT FROM AUTHOR]

One-dimensional heterostructure nanoarrays are efficiently promising as high performance electrodes for photo electrochemical (PEC) water splitting applications, wherein it is highly desirable for the electrode to have a broad light absorption, efficient charge separation and redox properties as well as defect free surface with high area suitable for fast interfacial charge transfer. We present highly active and unique photoelectrode for solar H2 production, consisting of silicon nanowires (SiNWs)/TiO2 core-shell structures. SiNWs are passivated to reduce defect sites and protected against oxidation in air or water by forming very thin carbon layer sandwiched between SiNW and TiO2 surfaces. This carbon layer decreases recombination rates and also enhances the interfacial charge transfer between the silicon and TiO2. A systematic investigation of the role of SiNW length and TiO2 thickness on photocurrent reveals enhanced photocurrent density up to 5.97 mA/cm2 at 1.0 Vvs.NHE by using C@SiNW/TiO2 nanoarrays with photo electrochemical efficiency of 1.17%. [ABSTRACT FROM AUTHOR]

Here we report a remarkable transformation of carbon nanotubes (CNTs) to nanoribbons composed of a few layers of graphene by a two-step electrochemical approach. This consists of the oxidation of CNTs at controlled potential, followed by reduction to form graphene nanoribbons (GNRs) having smooth edges and fewer defects, as evidenced by multiple characterization techniques, including Raman spectroscopy, atomic force microscopy, and transmission electron microscopy. This type of "unzipping" of CNTs (single-walled, multi-walled) in the presence of an interfacial electric field provides unique advantages with respect to the orientation of CNTs, which might make possible the production of GNRs with controlled widths and fewer defects. [ABSTRACT FROM AUTHOR]

Abstract: The effect of incorporating carbon nanotubes (CNTs) in the gel matrix on the electrophoretic mobility of proteins based on their molecular weight differences was investigated using sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). More specifically, a reduction in standard deviation in the molecular weight calibration plots by 55% in the case of multiwalled carbon nanotubes (MWCNTs) and by 34% in the case of single-walled carbon nanotubes (SWCNTs) compared with that of pristine polyacrylamide gels was achieved after incorporating an insignificant amount of functionalized CNTs into the gel matrix. A mechanism based on a more uniform pore size distribution in CNT modified polyacrylamide gel matrix is proposed. Furthermore, the impact of SWCNTs and MWCNTs on the mobility of proteins in different molecular weight regimes at a given acrylamide concentration offers a tunable gel matrix in terms of the selection of molecular weight ranges of proteins. The robustness and excellent reproducibility of the CNT–PAGE protocol are expected to have a significant impact on the molecular weight determination of newly isolated proteins. [Copyright &y& Elsevier]

Herein, we report that a copper complex [Cu(dpaq)](ClO4) (1) (H‐dpaq = 2‐[bis(pyridin‐2‐ylmethyl)]amino‐N‐quinolin‐8‐yl‐acetamide) acts as a molecular water oxidation catalyst (WOC) under strong basic condition. Complex 1 oxidizes water to dioxygen in 0.1 M phosphate buffer solution at pH 12.0, exhibiting a turnover frequency of 3.1 × 102 s−1 at a low overpotential (η) of ∼550 mV versus NHE at 1 mA cm−2. A turnover number of 4.0 can be obtained during controlled potential electrolysis (CPE) using 0.25 mM complex 1 at a potential of 1.5 V at pH 12.0 for 3 h. Postelectrolysis analysis, rinse tests, and chelating assays collectively support the homogeneous nature of the electrocatalyst. Mechanistic investigations and quantum chemical calculations reveal a pathway wherein two successive ligand‐centered oxidations transform the catalyst into a Cu(II)(dpaq•)O•. intermediate. Absence of any metal centered oxidation renders the oxidized intermediate less electrophilic, resulting in the survival of the methylene groups present on the ligand backbone against oxidation. The formation of the O─O bond is proposed to proceed via two consecutive single electron transfers (SET) from incoming hydroxide ions to the formal CuIV–oxo species. [ABSTRACT FROM AUTHOR]

In this report, the synthesis, characterization and electrocatalytic oxidation of water by a mononuclear cobalt(III) complex, [CoIII(dpaq)(Cl)]Cl (1) featuring a redox-active pentadentate amidate ligand (H-dpaq = 2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate) is reported. Complex 1 has been found to be a stable and homogeneous water oxidation catalyst (WOC) in 0.1 M phosphate buffer (pH 8.0). A series of experiments (rinse test, SEM, EDX spectroscopy) confirm that this complex acts as a molecular electrocatalyst, and not a precursor of CoOx. The electrocatalytic water oxidation proceeds with high faradaic efficiency (81%) and fast rate (85 s−1). Analysis of the electrochemical reaction kinetics by foot-of-the-wave (FOWA) methodology reveals a high turnover frequency of 1.6 × 104 s−1 which is comparable to the best performing Ru-based WOCs. [ABSTRACT FROM AUTHOR]

A Co(III)−hydroxo complex, [CoIII(dpaq)OH]ClO4 (1‐OH) bearing a pentadentate ligand, H‐dpaq, (H‐dpaq=(2‐[bis(pyridin‐2‐ylmethyl)]amino‐N‐quinolin‐8‐yl‐acetamidate]) catalyses water oxidation in mildly alkaline medium (pH 8.0) at a potential of 1.4 VNHE with an average Turn‐Over‐Frequency (TOFmax) of 2.8×104 s−1 and faradaic efficiency of 88 %. Post‐electrolysis characterization of the electrode rules out the formation of any heterogeneous electroactive species. Electrochemical results and theoretical calculations confirm the occurrence of both metal and ligand centered PCET processes during anodic scanning. The resulting formally Co(V)−oxo/oxyl intermediate undergoes water nucleophilic attack to install the O−O bond. The role of axial ligand in water oxidation by Co(III)−dpaq system has been examined by comparing the reactivity of the Co‐hydroxide complex (1‐OH) with that of its chloride‐ligated counterpart, [CoIII(dpaq)Cl]Cl (1‐Cl). The results confirm the ability of the Co‐dpaq complexes to bind water/or water derived ligands over chloride or non‐aqueous solvents. The interplay of ligand redox non‐innocence and σ‐donating ability of the N5‐carboxamido ligand helps to store oxidizing equivalents and triggers O−O bond formation. [ABSTRACT FROM AUTHOR]

Two-dimensional hexagonal boron carbon nitride (BCN) nanosheets (NSs) were synthesized by new approach in which a mixture of glucose and an adduct of boric acid (H3BO3) and urea (NH2CONH2) is heated at 900 °C. The method is green, scalable and gives a high yield of BCN NSs with average size of about 1 μm and thickness of about 13 nm. Structural characterization of the as-synthesized material was carried out by several techniques, and its energy-storage properties were evaluated electrochemically. The material showed excellent capacitive behaviour with a specific capacitance as high as 244 F g−1 at a current density of 1 A g−1. The material retains up to 96 % of its initial capacity after 3000 cycles at a current density of 5 A g−1. [ABSTRACT FROM AUTHOR]

Tailoring the physicochemical properties and hence reactivity of semiconductor photocatalysts in a predictable fashion, remains a challenge to their industrial application. Here we demonstrate the striking promotional effect of incorporating single Cu(I) atoms, on aqueous phase photocatalytic dye degradation and H 2 production over surfactant-templated mesoporous TiO 2 . X-ray absorption spectroscopy reveals that ultra-low concentrations of copper (0.02–0.1 wt%) introduced into the mesoporous TiO 2 surface create isolated Cu (I) species which suppress charge recombination, and confer a six-fold photocatalytic promotion of Methyl Orange degradation and four-fold enhancement of H 2 evolution. The impact of mesopore structure and photophysical properties on photocatalytic activity is also quantified for the first time: calcination increases mesopore size and nanocrystalline order, and induces an anatase to rutile phase transition that is accompanied by a decrease in the optical band gap, increased charge carrier lifetime, and a concomitant significant activity enhancement. [ABSTRACT FROM AUTHOR]

An important component of quantum dot sensitized solar cells (QDSSC) is the counter electrode which mediates the regeneration of oxidized quantum dots by reducing the polysulphide electrolyte. However, design and synthesis of an efficient counter electrode material is a challenging task. Herein, we report the synthesis of a unique Cu 2 S nanohusks directly on FTO coated glass substrates by electrodeposition and used as a counter electrode in QDSSC. When these electrodes are used for the reduction of polysulfide electrolyte in QDSSC, they exhibit higher catalytic activity and photovoltaic performance as compared to the Platinum counter electrode. The power conversion efficiency of about 4.68% has been achieved by optimizing the deposition time of Cu 2 S. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes (MWCNTs) have attracted extensive attention globally due to their applications in modern nanotechnology. It is very important to study the effects on these MWCNTs under swift heavy ion (SHI) irradiation since ion irradiation has been recognized as one of the best tools for nanostructuring of materials, in general. Here, we present the effects of 80 MeV Ni ions with a fluence ranging from 3×1012 to 3×1013 ions/cm2 on functionalized MWCNT mats. The properties of pristine and irradiated samples were studied using X-ray diffraction, Raman spectroscopy and transmission electron microscopy. The effects of SHI irradiation on these samples are discussed in detail. [ABSTRACT FROM AUTHOR]