Search

The modulated electron density of CeOx–NiB/SiC@NF electrode significantly boosts the electrochemically active surface area and electron transfer, which delivers excellent performance for HER and OER. And the electrode exhibits good stability.

A novel CeOx-NiB@NF catalyst with high activity and good stability towards both the HER and OER has been fabricated.

The development of efficient and cost-effective catalytic electrodes is of great importance to electrolysis. Herein, a strategy of fabricating practical catalytic electrodes by depositing conductive catalysts on inexpensive and easily accessible insulating substrates of paper, textiles and sponge has been realized and well developed. These electrodes are found to be highly active toward overall water splitting. As a distinctive example, the Ni–P–B/paper electrode affords 50 mA cm−2 at overpotentials of only 76 mV for the hydrogen evolution reaction and 263 mV for the oxygen evolution reaction, and can survive at large current density of 1000 mA cm−2 for over 240 h without apparent performance degradation in 1.0 M KOH. A two-electrode cell constructed by this paper electrode, which is only 1/5 the weight of a traditional metal electrode, delivered 50 mA cm−2 water-splitting current at a cell voltage of only 1.661 V, rivalling the integrated state-of-the-art Pt–C/Ni and IrO2/Ni electrode. Moreover, a functional Ni–P–B/paper ring electrode with in situ separation function has been constructed, enabling simultaneous generation, separation and collection of hydrogen and oxygen. This discovery may enable a large extension toward practical catalytic electrodes that are also active, cheap, light, flexible, earth-abundant and recyclable.

Low cost and effective transition metal based catalysts are critical to the development of hydrogen generation techniques. In this paper, a multifunctional nanosized Co B O material has been developed that can act as highly active catalyst for both hydrolytic and electrolytic hydrogen production, affording a hydrogen generation rate of 7.45 L min−1 g−1 for hydrolysis of sodium borohydride (NaBH4), and 10 mA cm−2 water-splitting current at overpotentials of 270 mV and 305 mV for hydrogen and oxygen evolution reaction in 1.0 M KOH. Meanwhile, oxygen doping is found to be critical to the activity of Co B O catalyst. This work will benefit the rational design of metal boride based material as highly active hydrolysis and electrolysis catalyst for hydrogen generation.

Precisely controlling the morphology of electrocatalyst which is critical to its activity and stability remains a key challenge toward efficient overall water splitting. Herein, a distinct temperature-dependent structure modulation effect of electroless plating technique is reported and consequently several bifunctional electrocatalysts with various structures are developed. The optimized bifunctional electrode with cobalt-phosphorus-boron nanoflowers growing on the carbon cloth demands overpotentials of only 91 mV and 294 mV to achieve a current density of 50 mA cm−2 for the hydrogen evolution reaction and oxygen evolution reaction in 1.0 M potassium hydroxide at 25 °C. Moreover, an overall water-splitting device assembled by this electrode can also work at high temperature of 60 °C with excellent long term durability and achieve a current density of 20 mA cm−2 at a cell voltage of around 1.39 V. This work uncovers some structure design principles of highly active electrocatalyst and provides a versatile strategy for structure modulation of the electrocatalyst for pratctical water electrolysis.

Mesoporous NiO/reduced graphene oxide composites are successfully synthesized by a facile hydrothermal route. The XRD, FT-IR, Raman, SEM, TEM, and BET analysis are performed for characterizing the microstructure of the as-prepared composites. It can be found that the NiO particles with mesoporous structure are randomly anchored onto the surface of graphene sheets. The electrochemical performance is evaluated by CV, EIS and galvanostatic charge-discharge tests. Experimental data show that the NiO/RGO composites exhibit very high specific capacitance (1016.6 F g −1 ) and excellent cycling stability (94.9% capacitance retention after 5000 cycles), which are due to the 3D graphene conductive network and the meosporous structure promoting efficient charge transport and electrolyte diffusion. The results suggest that the NiO/RGO composites are a promising supercapacitor electrode material.

Two diphenyl thioether-bridged binuclear metallocenes of Ti and Zr, [(C5H5)Cl2MC5H4CH2(p-C6H4)]2S [M = Ti (1) and Zr (2)], have been synthesized by treating the dilithium salts of the corresponding ligand [(C5H5CH2(p-C6H4)]2S with two equivalents of C5H5TiCl3 and C5H5ZrCl3(DME), respectively, in toluene at 0°C. Both new complexes have been characterized by 1H-NMR spectroscopy and elemental analysis. Homogeneous ethylene polymerization using both complexes was performed in the presence of methylaluminoxane (MAO). The influences of molar ratio of [MAO]/[Cat], concentration of the catalysts, time, and temperature have been studied systematically. The catalytic activity of 1 is higher than that of the corresponding oxygen-bridged catalyst [(C5H5)Cl2TiC5H4CH2(p-C6H4)]2O. The catalytic activity of 2 is at least two times higher than that of 1 under any tested polymerization conditions. The melting points of polyethylene (PE) produced by 1 and 2 are higher than 130°C, indicating a highly linear and highly crystalline PE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

The condensation of acetylacetone (CH3COCH2COCH3) with benzdine (H2N-C6H4-C6H4-NH2) yielded diimine ligand 1 HOC(Me)C(H)(Me)C=N(p-C6H4)(C6H4-p)N=C(Me)C(H)C(Me)OH), which was converted into sodium salts. And then the sodium salts reacted with monosalicylaldiminato titanium complex 2{3,5-di-But-2-(O)C6H2CHN(PH) TiCl3(THF)} in dried dichloromethane to give a new benzdine-bridged binuclear complex 3{3,5-di-But-2-(O)C6H2CHN(PH) 2 OC(Me)C(H)(Me)C=N(p-C6H4)-(C6H4-p)N=C(Me)C(H) C(Me) Ti2Cl4}. The complex 3 was characterized by 1HNMR and elemental analysis. In the presence of MAO (methylaluminoxane), the complex 3 in toluene was effective to catalyze polymerization, affording moderately high catalytic activity 1.93×10^5 g PE/(mol•Ti•h)] and high molecular weight polyethylene [5.63×10^5 g/mol]. The high temperature gel permeation chromatography (GPC) curve of polyethylene obtained revealed a single peak, but the molecular weight distribution (MWD=3.21) is obviously broader than that of the similar mononuclear titanium complex. The melting points of the obtained polyethylene reaches 138℃, indicating that the polyethylene is of high crystallinity.

Three novel methylene bridged binuclear iron(II) complexes: { [ 2 , 6 -R 2 -C 6 H 3 N C ( CH 3 ) C 5 H 3 N ( CH 3 ) C N ( 3 , 5 -R 2 ′ ) C 6 H 2 -CH 2 - ( 3 , 5 -R 2 ′ ) C 6 H 2 N C ( CH 3 ) C 5 H 3 N ( CH 3 ) C N ( 2 , 6 -R 2 ) C 6 H 3 ] [ FeCl 2 ] 2 (R,R′ = i -C 3 H 7 ( 6 ); R = i -C 3 H 7 , R′ = CH 3 ( 7 ); R,R′ = CH 3 ( 8 ))} have been synthesized. Activated by Al( i -Bu) 3 , complex 6 shows very poor activity for the polymerization of ethylene at one bar ethylene pressure, whereas, 7 and 8 exhibit much higher activity than mononuclear iron catalysts {[ArN C(Me)C 5 H 3 N(Me)C NAr′]FeCl 2 (Ar,Ar′ = 2,6-C 6 H 3 - i -Pr ( 9 ); Ar = 2,6-C 6 H 3 - i -Pr 2 , Ar′ = 2,6-C 6 H 3 –Me 2 ( 10 ); Ar,Ar′ = 2,6-C 6 H 3 –Me 2 ( 11 ))}. The molecular weight ( M w ) of PE produced by 7 and 8 are in the range 13.2–46.0 × 10 4 and much higher than those produced by mononuclear iron catalysts 9 and 10 . GPC results demonstrate that 7 and 8 yield PE with a broad/bimodal molecular weight distribution (MWD). In contrast, 9 and 10 yield PE with relatively narrow and unimodal MWD (4.26 and 3.55). Elevating the temperature and Al/Fe molar ratio will narrow the MWD of PE.

New catalytic systems, composed of bis(imino)pyridine (2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine (A1), methylene-bridged bis(imino)pyridine (A2)), iron (III) acetylacetonate (Fe(acac)3), and methylaluminoxane (MAO), are highly active for ethylene polymerization. The performance of this new catalytic system was evaluated with respect to catalytic activity and polymer properties. The highest catalytic activity of Fe(acac)3-A1/MAO (catA) system and Fe(acac)3-A2/MAO (catB) system at optimum condition reaches 10.5 × 106 g PE·(mol Fe h)−1 and 17.3 × 106 g PE·(mol Fe h)−1, respectively. The product viscosity-average molecular weight (Mη) of two catalytic systems range from 0.40 to 8.7 × 105. GPC characterizations of PE obtained show that the PE has bimodal molecular weight distribution (MWD). 13C NMR and DSC analysis of PE sample indicates that the PE is highly linear and crystalline. Analysis of UV–vis absorption spectra, ethylene polymerization results, and prepared polyethylene structures indicate that Fe(acac)3-bis(imino)pyridine/MAO catalytic system could generate same active species as bis(imino)pyridyliron catalytic systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Three vanadocene-cocatalyst catalytic systems for ethylene polymerization-Cp 2 ZrCl 2 /Al 2 Et 3 Cl 3 [dichlorobis(η-cyclopentadienyl)vanadium/ethylaluminumsesquichloride], Cp 2 ZrCl 2 /MAO [dichlorobis(η-cyclopentadienyl)vanadium/methylaluminoxane] and Cp 2 ZrCl 2 /AlEt 3 [dichlorobis(η-cyclopentadienyl)vanadium/triethylaluminum]-were monitored by electron spin resonance (ESR) spectroscopy. It was found that at least a certain kind of vanadium complex is formed after mixing dichlorobis(η-cyclopentadienyl)vanadium with ethylaluminumsesquichloride. After introducing ethylene, a new kind of vanadium complex is detected by ESR. Ethylene can be polymerized by using a dichlorobis(η-cyclopentadienyl)vanadium/ethylaluminumsesquichloride catalytic system. These results possibly indicate that the vanadium complex exists in the forms ClCp 2 VClEtAlCl 2 and ClCp 2 VClEtAlClEt, which are responsible for forming active centers. The Dichlorobis(η-cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η-cyclopentadienyl)vanadium/triethylaluminum systems also were monitored by ESR. Completely different spectra were recorded compared to those of the dichlorobis(η-cyclopentadienyl) vanadium/ethylaluminumsesquichloride system. Ethylene almost cannot be polymerized by the dichlorobis(η-cyclopentadienyl)vanadium/ methylaluminoxane and dichlorobis(η-cyclopentadienyl)vanadium/triethylaluminum catalytic systems, showing that resultant vanadium complexes of dichlorobis(η-cyclopentadienyl)vanadium/methylaluminoxane and dichlorobis(η-cyclopentadienyl)vanadium/triethylaluminum catalytic systems are different from that arising from the dichlorobis(η-cyclopentadienyl)vanadium/ethylaluminumsesquichloride system. Plausible mechanisms are suggested for this.

Polyethylene was prepared by using a nBu-Cp2ZrCl2/MAO catalytic system. Considering the reactivation of Zr species, a novel and reasonable mathematical model of kinetics has been developed and the kinetic profiles of ethylene polymerization have been fitted satisfactorily. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3186–3189, 2001