Molybdenum iron carbide-copper hybrid as efficient electrooxidation catalyst for oxygen evolution reaction and synthesis of cinnamaldehyde/benzalacetone.

Oxygen evolution reaction (OER) is the efficiency limiting half-reaction in water electrolysis for green hydrogen production due to the 4-electron multistep process with sluggish kinetics. The electrooxidation of thermodynamically more favorable organics accompanied by CC coupling is a promising way to synthesize value-added chemicals instead of OER. Efficient catalyst is of paramount importance to fulfill such a goal. Herein, a molybdenum iron carbide-copper hybrid (Mo2C-FeCu) was designed as anodic catalyst, which demonstrated decent OER catalytic capability with low overpotential of 238 mV at response current density of 10 mA cm-2 and fine stability. More importantly, the Mo2C-FeCu enabled electrooxidation assisted aldol condensation of phenylcarbinol with α-H containing alcohol/ketone in weak alkali electrolyte to selective synthesize cinnamaldehyde/benzalacetone at reduced potential. The hydroxyl and superoxide intermediate radicals generated at high potential are deemed to be responsible for the electrooxidation of phenylcarbinol and aldol condensation reactions to afford cinnamaldehyde/benzalacetone. The current work showcases an electrochemical-chemical combined CC coupling reaction to prepare organic chemicals, we believe more widespread organics can be synthesized by tailored electrochemical reactions.

Molybdenum, tungsten doped cobalt phosphides as efficient catalysts for coproduction of hydrogen and formate by glycerol electrolysis.

H2 and formate are important energy carriers in fuel-cells and feedstocks in chemical industry. The hydrogen evolution reaction (HER) coupling with electro-oxidative cleavage of thermodynamically favorable polyols is a promising way to coproduce H2 and formate via electrochemical means, highly active catalysts for HER and electrooxidative cleavage of polycols are the key to achieve such a goal. Herein, molybdenum (Mo), tungsten (W) doped cobalt phosphides (Co2P) deposited onto nickel foam (NF) substrate, denoted as Mo-Co2P/NF and W-Co2P/NF, respectively, were investigated as catalytic electrodes for HER and electrochemical glycerol oxidation reaction (GOR) to yield H2 and formate. The W-Co2P/NF electrode exhibited low overpotential (η) of 113 mV to attain a current density (J) of -100 mA cm-2 for HER, while the Mo-Co2P/NF electrode demonstrated high GOR efficiency for selective production of formate. In situ Raman and infrared spectroscopic characterizations revealed that the evolved CoO2 from Co2P is the genuine catalytic sites for GOR. The asymmetric electrolyzer based on W-Co2P/NF cathode and Mo-Co2P/NF anode delivered a J = 100 mA cm-2 at 1.8 V voltage for glycerol electrolysis, which led to 18.2 % reduced electricity consumption relative to water electrolysis. This work highlights the potential of heteroelement doped phosphide in catalytic performances for HER and GOR, and opens up new avenue to coproduce more widespread commodity chemicals via gentle and sustainable electrocatalytic means.

Amorphous-crystalline heterostructures enable energy-level matching of cobalt sulfide/nickel iron layered double hydroxide for efficient oxygen evolution reaction.

Interface engineering of heterostructures has emerged as a promising approach to enhance the catalytic activity of nonprecious electrocatalysts. Herein, a novel amorphous cobalt sulfide-crystalline nickel iron layered double hydroxide (a-CoS@NiFe-LDH) hybrid material is presented for application as an electrocatalyst for oxygen evolution reaction (OER). Benefitting from the well-matched energy level structures, the a-CoS@NiFe-LDH catalyst delivers a low overpotential of 221 ± 14 mV at an OER current density of 20 mA cm-2 and a small Tafel slope of 83.1 mV dec-1, showing good OER properties. First-principle computations reveal that the electronic interaction between amorphous cobalt sulfide (a-CoS) and crystalline nickel iron layered double hydroxide (NiFe-LDH) components within a-CoS@NiFe-LDH promotes the adsorbate evolution mechanism and reduces the adsorption energies for oxygen intermediates, thereby enhancing the activity and stability for OER. This work opens up a new avenue to enhance the OER catalytic efficiency via the construction of amorphous-crystalline heterostructures.

Self-supported amorphous phosphide catalytic electrodes for electrochemical hydrogen production coupling with methanol upgrading.

Efficient catalytic electrodes for cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) are pivotal for massive production of green hydrogen from water electrolysis, and the further replacement of kinetically sluggish OER by tailored elecrooxidation of certain organics is a promising way to co-produce hydrogen and value-added chemicals via a more energy-saving and safer manner. Herein, amorphous Ni-Co-Fe ternary phosphides (NixCoyFez-Ps) with different Ni:Co:Fe ratios electrodeposited onto Ni foam (NF) substrate were served as self-supported catalytic electrodes for alkaline HER and OER. The Ni4Co4Fe1-P electrode deposited in solution at Ni:Co:Fe ratio of 4:4:1 displayed low overpotential (61 mV at -20 mA cm-2) and acceptable durability for HER, while the Ni2Co2Fe1-P electrode fabricated in deposition solution at Ni:Co:Fe ratio of 2:2:1 showed good OER efficiency (overpotential of 275 mV at 20 mA cm-2) and robust durability, the further replacement of OER by anodic methanol oxidation reaction (MOR) enabled selective production of formate with 110 mV lower anodic potential at 20 mA cm-2. The HER-MOR co-electrolysis system based on Ni4Co4Fe1-P cathode and Ni2Co2Fe1-P anode could save 1.4 kWh of electric energy per cubic meter of H2 relative to mere water electrolysis. The current work offers a feasible approach to co-produce H2 and value-upgraded formate via an energy-saving manner by rational design of catalytic electrodes and construction of co-electrolysis system, and paves the way for cost-effective co-preparation of more value-added organics and green hydrogen via electrolysis.

Hierarchical bismuthyl bromide microspheres assembled by laminas as efficient negative material for aqueous alkali battery.

Bismuth (Bi) based compounds are promising negative materials in aqueous alkali batteries (AABs) for the 3-electron redox chemistry of Bi element within low potentials, the exploration of new Bi-based negative materials is still a meaningful work in this field. Herein, a hierarchical bismuthyl bromide (BiOBr) microspheres material assembled by laminas was prepared via solvothermal reaction and attempted as negative battery material for AAB. The pronounced redox reactions of Bi species in low potential enable high battery capacity, and the porous texture with high hydrophilicity facilitates diffusion of OH- and participation in faradaic reactions. When used as negative battery electrode, the BiOBr could offer decent specific capacity (Cs, 190 mAh g-1 at 1 A g-1), rate capability (Cs remained to 163 mAh g-1 at 8 A g-1) and cycleability (85% Cs retention after 1000 charge-discharge cycles). The AAB based on BiOBr negative electrode could export an energy density (Ecell) of 61.5 Wh kg-1 at power density (Pcell) of 558 W kg-1 and good cycleability. The current work showcases valuable application expansion of a traditional BiOBr photocatalyst in battery typed charge storage.

Prussian blue analog-derived nickel iron phosphide-reduced graphene oxide hybrid as an efficient catalyst for overall water electrolysis.

Efficient and bifunctional nonprecious catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) are essential for the production of green hydrogen via water electrolysis. Transition metal (Ni, Co, Fe, etc.) phosphides are frequently documented HER catalysts, whereas their bimetallic oxides are efficient OER catalysts, thus enabling bifunctional catalysis for water electrolysis via proper operation. Herein, phosphide-reduced graphene oxide (rGO) hybrids were prepared from graphene oxide (GO)-incorporated bimetal Prussian blue analog (PBA) precursors. The hybrids could experience partial surface oxidation to create oxide layers with OER activities, and the hybrids also possessed considerable HER properties, therefore enabling bifunctional catalytic features for water electrolysis. The typical NiFeP-rGO hybrid demonstrated an overpotential of 250 mV at 10 mA cm-2 and good durability for OER, as well as moderate HER catalytic features (overpotential of 165 mV at -10 mA cm-2 and acceptable catalytic stability). Due to the bifunctional catalytic features, the NiFeP-rGO-based symmetric water electrolyzer demonstrated a moderate input voltage and high faradaic efficiency (FE) for O2 and H2 production. The current work provides a feasible way to prepare OER and HER bifunctional catalysts by facile phosphorization of PBA-associated precursors and spontaneous surface oxidation. Given the oxidation/reduction bifunctional catalytic behaviors, phosphide-rGO hybrid catalysts have great potential for widespread application in fields beyond water electrolysis, such as electrochemical pollution abatement, sensors, energy devices and organic syntheses.

Bismuth oxyformate microspheres assembled by ultrathin nanosheets as an efficient negative material for aqueous alkali battery.

A negative electrode with high capacity and rate capability is essential to match the capacity of a positive electrode and maximize the overall charge storage performance of an aqueous alkali battery (AAB). Due to the 3-electron redox reactions within a wide negative potential range, bismuth (Bi)-based compounds are recognized as efficient negative electrode materials. Herein, hierarchically structured bismuth oxyformate (BiOCOOH) assembled by ultrathin nanosheets was prepared by a solvothermal reaction for application as negative material for AAB. Given the efficient ion diffusion channels and sufficient exposure of the inner surface area, as well as the pronounced 3-electron redox activity of Bi species, the BiOCOOH electrode offered a high specific capacity (Cs, 229 ± 4 mAh g-1 at 1 A g-1) and superior rate capability (198 ± 6 mAh g-1 at 10 A g-1) within 0 âˆ¼ -1 V. When pairing with the Ni3S2-MoS2 battery electrode, the AAB delivered a high energy density (Ecell, 217 mWh cm-2 at a power density (Pcell) of 661 mW cm-2), showing the potential of such a novel BiOCOOH negative material in battery-type charge storage.

Self-supported molybdenum nickel oxide catalytic electrode designed via molecular cluster-mediated electroplating and electrochemical activation for an efficient and durable oxygen evolution reaction.

Efficient and durable nonprecious catalysts for the oxygen evolution reaction (OER) are crucial for practical water electrolysis for hydrogen production. A self-supported OER catalytic electrode with sufficient exposure of the catalyst and tight anchoring onto the current collector is vital for the catalytic activity and stability, and is therefore deemed to be a preferable tactic to enhance water electrolysis performance. Herein, a polyoxometalate (POM) molecular cluster-mediated electroplating and activation tactics are proposed to design a self-supported molybdenum nickel oxide (MoNiOx) catalytic electrode for the OER. The MoNiOx active layer can anchor tightly onto the Ni foam current collector with sufficient surface exposure and high structural stability, therefore enabling high alkali OER catalytic efficiency (222 mV at 10 mA cm-2) and robust durability (only slight decay in catalytic efficiency upon 12 days of chronopotentiometry (V-t) test). Moreover, the easily processable electroplating and active protocol can serve as a general approach to prepare other OER catalytic electrodes by altering the reactants and current collectors. The current work paves a facile and universal way to design a highly active and durable molybdenum (Mo) based hybrid catalytic electrode for OER via molecular cluster-assisted electroplating and activation treatment.

Molybdenum oxide-iron, cobalt, copper alloy hybrid as efficient bifunctional catalyst for alkali water electrolysis.

Efficient and durable non-precious catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is pivotal for practical water electrolysis toward clean hydrogen fuel. Herein, a molybdenum oxide-FeCoCu alloy hybrid (MoOx-FeCoCu) catalyst was designed by polyoxometallate (POM) molecular cluster mediated solvothermal alcoholysis and ammonolysis of metal salts followed by pyrolytic reduction treatment. The HER efficiency is substantially enhanced by the ternary alloy component, which is more close to the benchmark Pt/C catalyst, and the HER catalytic stability is also superior to Pt/C catalyst. Moreover, the MoOx-FeCoCu demonstrates high catalytic efficiency and rather good durability for OER. Benefitted by the bifunctional catalytic behaviors for HER and OER, the symmetric water electrolyzer based on the MoOx-FeCoCu electrode requires a low driving voltage of 1.69 V to deliver a response current density of 10 mA cm-2, which is comparable to that based on the benchmark Pt/C HER cathode and RuO2 OER anode. The current work offers a feasible way to design efficient bifunctional catalyst for water electrolysis via POM mediated co-assembly and calcination treatment.

Enhanced faradic activity by construction of p-n junction within reduced graphene oxide@cobalt nickel sulfide@nickle cobalt layered double hydroxide composite electrode for charge storage in hybrid supercapacitor.

The intrinsic faradic reactivity is the uppermost factor determining the charge storage capability of battery material, the construction of p-n junction composing of different faradic components is a rational tactics to enhance the faradic activity. Herein, a reduced graphene oxide@cobalt nickle sulfide@nickle cobalt layered double hydroxide composite (rGO@CoNi2S4@NiCo LDH) with p-n junction structure is designed by deposition of n-type nickle cobalt layered double hydroxide (NiCo LDH) around p-type reduced graphene oxide@cobalt nickle sulfide (rGO@CoNi2S4), the charge redistribution across the p-n junction enables enhanced faradic activities of both components and further the overall charge storage capacity of the resultant rGO@CoNi2S4@NiCo LDH battery electrode. As expected, the rGO@CoNi2S4@NiCo LDH electrode can deliver high specific capacity (Cs, 1310 ± 26 C g-1 at 1 A g-1) and good cycleability (77% Cs maintaining ratio undergoes 5000 charge-discharge cycles). Furthermore, the hybrid supercapacitor (HSC) based on the rGO@CoNi2S4@NiCo LDH p-n junction battery electrode exports high energy density (Ecell, 57.4 Wh kg-1 at 323 W kg-1) and good durability, showing the prospect of faradic p-n junction composite in battery typed energy storage.

The effect of Fe(III) cations in electrolyte on oxygen evolution catalytic activity of Ni(OH)2 electrode.

A facile and efficient oxygen evolution reaction (OER) catalytic system was constructed based on interconnected Ni(OH)2 nanosheets arrays electrode and Fe(III) containing alkali electrolyte. The partial deposition of Fe(III) onto Ni(OH)2 with heterostructure obviously enhanced the OER current density and reduced the overpotential, and the Fe(III) cations in electrolyte also furnished positive contribution to the catalytic reaction, the synergy between Ni(OH)2 electrode and Fe(III) cations in electrolyte therefore substantially improved the OER catalytic efficiency with low overpotential (285 mV at current density of 50 mA cm-2) and obviously enhanced current density (391 mA cm-2 at 1.8 V). The current work expands our understanding on the effect of Fe(III) cations in electrolyte to OER efficiency of Ni based catalyst, and opens up a cost-effective and practical avenue to enhance the OER catalytic efficiency by introducing metal cations in alkali electrolyte.

Fluorine anion-enriched nickel hydroxyl oxide as an efficient oxygen evolution reaction electrocatalyst.

F- anion-enriched Ni hydroxyl oxide (F-NHO) mesocrystalline microspheres were prepared by a facile hydrothermal hydrolysis of a Ni precursor mediated by NH4F. The quasi monocrystalline structure, superhydrophilic surface and high F- anion-doping level of F-NHO enable high catalytic efficiency for the oxygen evolution reaction in the electrolysis of water.

Highly fluorescent carbon dots as an efficient nanoprobe for detection of clomifene citrate.

Highly fluorescent carbon dots (CDs) were synthesized through facile hydrothermal carbonization and ethylenediamine passivation of an easily available prawn shell precursor. The as-prepared CDs exhibit high water solubility, wavelength-tunable fluorescence with quantum yield up to 68.9%, high photostability and resistance against biomolecules, thus enabling the application as viable fluorescent nanoprobes for detection of guest quenchers. The fluorescence of the CDs can be effectively quenched by clomifene citrate (CC, a common drug for infertility) through static quenching, and therefore can serve as a simple and efficient fluorescent nanoprobe for determination of CC with wide linear range (0.25-10 µg mL-1) and low detection limit (0.2 µg mL-1). The CDs also showed low cytotoxicity, which enables the safe and accurate fluorescent detection of spiked CC in human serum, demonstrating their potential as a credible fluorescent CC nanoprobe in clinical examination.

Fish-scale-derived carbon dots as efficient fluorescent nanoprobes for detection of ferric ions.

Herein, highly fluorescent carbon dots (CDs) with the incorporation of N and O functionalities were prepared through a facile and cost-effective hydrothermal reaction using fish scales of the crucian carp as the precursor. The as-prepared CDs exhibit strong fluorescent emissions at 430 nm with a relative quantum yield of 6.9%, low cytotoxicity, and robust fluorescence stability against photobleaching and good ionic strength. More significantly, the fluorescence of these CDs can be effectively and selectively quenched by Fe3+ ions, which enables the application of CDs as fluorescent Fe3+ nanoprobes with a linear range of 1-78 µmol L-1 and a detection limit of 0.54 µmol L-1. The proposed fluorescent CD nanoprobes can also be used for the assay of spiked Fe3+ in real water samples and human serums with high recoveries and low standard deviations. Hence, CDs can be potentially applied as safe and reliable fluorescent nanoprobes for environmental and clinical Fe3+ analyses.

Micelles directed preparation of ternary cobalt hydroxide carbonate-nickel hydroxide-reduced graphene oxide composite porous nanowire arrays with superior faradic capacitance performance.

Electrode material is the key component of a supercapacitor, the highly accessible surface area, efficient electrons/ions migration channels, robust structural stability and redox activity of electrode material are pivotal prerequisites for harvesting optimal capacitive performance. Herein, a ternary cobalt hydroxide carbonate-nickle hydroxide-reduced graphene oxide composite (CN-rGO) with porous nanowire arrays architecture was deposited onto Ni foam substrate through confined hydrothermal reaction directed by surfactant micelles. The as-prepared CN-rGO nanowire arrays exhibit mesoporous texture with high specific surface area, which allows sufficient soaking of electrolyte with short diffusion path length. Additionally, the vertically aligned nanowires with incorporation of reduced graphene oxide offer efficient channels for migration of electrons generated by faradic components. Both features enable the sufficient faradic reactions and charge storage of the CN-rGO electrode. Under optimal Co:Ni feeding molar ratio of 7:3, the battery typed faradic CN-rGO electrode offers superior specific capacitance (2442 F g-1 at 1 A g-1), good rate capability (65% capacitance retaining ratio within 1-20 A g-1) and cycling stability (70% maintaining ratio after 2000 charge-discharge cycles). When used as faradic electrode of hybrid supercapacitor (HSC), balanced energy density (42.9-26.2 Wh kg-1), power density (393-3519 W kg-1) and cycleability (80% initial capacitance maintaining ratio undergoes 5000 charge-discharge cycles) can be delivered simultaneously, highlighting the potential of the micelles directed CN-rGO nanowire arrays electrode in efficient energy storage device.

Nitrogen-Doped Porous Carbons As Electrode Materials for High-Performance Supercapacitor and Dye-Sensitized Solar Cell.

Activated N-doped porous carbons (a-NCs) were synthesized by pyrolysis and alkali activation of graphene incorporated melamine formaldehyde resin (MF). The moderate N doping levels, mesopores rich porous texture, and incorporation of graphene enable the applications of a-NCs in surface and conductivity dependent electrode materials for supercapacitor and dye-sensitized solar cell (DSSC). Under optimal activation temperature of 700 °C, the afforded sample, labeled as a-NC700, possesses a specific surface area of 1302 m2 g(-1), a N fraction of 4.5%, and a modest graphitization. When used as a supercapacitor electrode, a-NC700 offers a high specific capacitance of 296 F g(-1) at a current density of 1 A g(-1), an acceptable rate capability, and a high cycling stability in 1 M H2SO4 electrolyte. As a result, a-NC700 supercapacitor delivers energy densities of 5.0-3.5 Wh kg(-1) under power densities of 83-1609 W kg(-1). Moreover, a-NC700 also demonstrates high electrocatalytic activity for I3- reduction. When employed as a counter electrode (CE) of DSSC, a power conversion efficiency (PCE) of 6.9% is achieved, which is comparable to that of the Pt CE based counterpart (7.1%). The excellent capacitive and photovoltaic performances highlight the potential of a-NCs in sustainable energy devices.

Solvothermal synthesis of antimony sulfide dendrites for electrochemical detection of dopamine.

Sb2S3 dendrites composed of 1-dimensional rods were prepared by a facile solvothermal reaction. The dosage of the poly(acrylic acid) (PAA) morphology-controlling reagent and the reaction temperature are key factors determining the final morphology of the product. Temporal experiments revealed that the formation of Sb2S3 dendrites experienced successive stages including precipitate reaction, crystallization and tip splitting. The as-prepared Sb2S3 dendrites were further employed as sensing material for electrochemical detection of dopamine (DA). A cyclic voltammogram (CV) showed that an Sb2S3 dendrite modified electrode enables the selective electro-oxidation of DA in the presence of ascorbic acid (AA). The constructed biosensor demonstrated a linear response range of 0.125-160 µM and a detection limit of 0.1 µM, which suggests that the Sb2S3 dendrites are promising sensing materials in the electrochemical analysis of DA.

Hierarchical titania mesoporous sphere/graphene composite, synthesis and application as photoanode in dye sensitized solar cells.

Hierarchical TiO(2) mesoporous sphere/graphene composites (HTMS/Gs) were prepared by incorporation proper amounts of graphene oxide (GO) into the reaction system toward hierarchical TiO(2) mesoporous spheres (HTMSs). The HTMS/Gs inherit the merits of high specific surface area derived from both HTMS and graphene, as well as the well conductivity of graphene. Power conversion efficiencies (PCEs) of dye sensitized solar cells (DSSCs) using HTMS/Gs as photoanode materials were also investigated. The graphene content in HTMS/G exhibited great influence on PCE. Lower graphene content in HTMS/G showed superior dye adsorption capacity, lower charge recombination and thus higher photocurrent density over bare HTMS. However, excessive graphene promoted the recombination of photo-generated electrons, which deteriorated the PCE. Due to the high dye adsorption capacity and the prolonged electron recombination lifetime, the HTMS/G contains 5.68 wt.% graphene, denoted as HTMS/G(5.68), boosted up the short circuit current density (J(sc)) to 16.17 mA/cm(2), and a PCE of 7.19% was achieved, which is 21.8% higher than that of bare HTMS.

4,4,5,5-Tetra-methyl-2-(4-pyridinio)-2-imidazoline-1-oxyl-3-oxide perchlorate.

The crystal structure of the title compound, C(12)H(17)N(3)O(2) (+)·ClO(4) (-), consists of 4,4,5,5-tetra-methyl-2-(4-pyridinio)imidazoline-1-oxyl-3-oxide radical cations and perchlorate anions. Both the cation and the Cl atom of the anion are located on the same twofold rotation axis, and the crystal structure shows the average structure for the radical cation. The five-membered ring assumes a half-chair conformation. The cation links with the anion via N-H⋯O hydrogen bonding.

1,2-Bis[(2-hydr-oxy-3-methoxy-benzyl-idene)hydrazono]-1,2-diphenyl-ethane.

The title compound, C(30)H(26)N(4)O(4), was synthesized by the reaction of benzyl dihydrazone and 2-hydr-oxy-3-methoxy-benzaldehyde in ethanol. In the crystal strucutre, the mol-ecule is centrosymmetric. The structure displays two symmetry-related intra-molecular O-H⋯N hydrogen bonds.