Fang-Zu Yang

Synthesis, Characterization and Electrochemical Properties of Stable Osmabenzenes Containing PPh3 Substituents

Treatment of [OsCl(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond]CH/PPh(3) produces the osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Cl(2)(PPh(3))(2)][OH] (2), which is air stable in both solution and solid state. The key intermediate of the one-pot reaction, [OsCl(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (3), and the related complex [Os(NCS)(2){CHC(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (7) have been isolated and characterized, further supporting the proposed mechanisms for the reaction. Reactions of 3 with PPh(3), NaI, and NaSCN give osmabenzene 2, iodo-substituted osmabenzene [Os{CHC(PPh(3))CHCICH}I(2)(PPh(3))(2)] (4), and thiocyanato-substituted osmabenzene [Os{CHC(PPh(3))CHC(SCN)CH}(NCS)(2)(PPh(3))(2)] (5) respectively. Similarly, reaction of [OsBr(2)(PPh(3))(3)] with HC[triple bond]CCH(OH)C[triple bond] CH in THF produces [OsBr(2){CH=C(PPh(3))CH(OH)C[triple bond]CH}(PPh(3))(2)] (9), which reacts with PPh(3)/Bu(4)NBr to give osmabenzene [Os{CHC(PPh(3))CHC(PPh(3))CH}Br(2)(PPh(3))(2)]Br (10). Ligand substitution reactions of 2 produce a series of new stable osmabenzenes 11-17. An electrochemical study shows that osmabenzenes 2, 12, and 14-17 have interesting different electrochemical properties due to the different co-ligand. The oxidation potentials of complexes 2, 12, 16, and 17 with Cl, NCS, and N(CN)(2) ligands gradually positively shift in the sequence of Cl<NCS<N(CN)(2). Among the six compounds, only 12 and 17 undergo a well-behaved, nearly reversible and a quasi-reversible reduction process, respectively, indicating that two NCS or N(CN)(2) ligands contribute to the stabilization of their reduced states.

Synthesis and characterization of a novel dialdehyde and cyclic anhydride

The acid treatment of a ruthenabenzene yielded an unusual dialdehyde. Interestingly, this dialdehyde has notable anti-oxidative properties and resists even nitric acid. This stability is confirmed by chemical and electrochemical experiments. In addition, a stable cyclic anhydride is synthesized from the dialdehyde via an environmentally friendly electrochemical method.

A density functional theory approach to mushroom-like platinum clusters on palladium-shell over Au core nanoparticles for high electrocatalytic activity.

Recently, it was found that Pt clusters deposited on Pd shell over Au core nanoparticles (Au@Pd@Pt NPs) exhibit unusually high electrocatalytic activity for the electro-oxidation of formic acid (P. P. Fang, S. Duan, et al., Chem. Sci., 2011, 2, 531-539). In an attempt to offer an explanation, we used here carbon monoxide (CO) as probed molecules, and applied density functional theory (DFT) to simulate the surface Raman spectra of CO at this core-shell-cluster NPs with a two monolayer thickness of Pd shell and various Pt cluster coverage. Our DFT results show that the calculated Pt coverage dependent spectra fit the experimental ones well only if the Pt clusters adopt a mushroom-like structure, while currently the island-like structure is the widely accepted model, which follows the Volmer-Weber growth mode. This result infers that there should be a new growth mode, i.e., the mushroom growth mode as proposed in the present work, for Au@Pd@Pt NPs. We suggest that such a mushroom-like structure may offer novel active sites, which accounts for the observed high electrocatalytic activity of Au@Pd@Pt NPs.

Electrochemical study on electroless copper plating using sodium hypophosphite as reductant

Abstract The process of electroless copper plating, using sodium hypophosphite as the reductant and sodium citrate as the chelating agent, was studied using liner sweep voltammetry. The effects of temperature, pH, and concentration of nickel ion on the anodic oxidation of hypophosphite and the cathodic reduction of copper ion were tested. The results indicated that the higher bath temperature accelerated both the anodic and the cathodic processes. The increasing pH value promoted hypophosphite oxidation, whereas it blocked the reduction of the copper ion. The nickel ion not only intensively catalyzed the hypophosphite oxidation but also codeposited with the copper ion to form the Cu-Ni alloy. With regard to its catalytic activity, this alloy enabled the continuation of the electroless copper plating reaction.

Studies on the mechanism, structure and microhardness of Ni-W alloy electrodeposits

SUMMARYThe electrodeposition of Ni-W alloy has been studied on the glassy carbon electrode by the cyclic voltammetry and potentiostatic step methods. It has been found that electrodeposition of Ni-W alloy involves an intermediate valence tungsten oxide which inhibits hydrogen evolution. Ni-W alloy electrodeposition occurs by a mechanism involving progressive nucleation followed by three dimensional growth.The structures of nickel-tungsten alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD results from Ni-W alloy deposits reveal a face-centered cubic solid solution, the microstructure of the deposits exhibit (111) preferred orientation. The lattice constant and microhardness of Ni-W alloy deposit increase as the tungsten content increases, the XPS results of Ni-W alloy deposits indicate that the nickel and tungsten of the deposits exist in the metallic state, but the Ni-W alloy deposit with a tungsten content of 40.7% is an intermetallic compound. Th...

Electrochemical nucleation and growth of copper on HOPG in presence of PEG and chloride ions as additives

Abstract Initial stages of copper electrodeposition on highly oriented pyrolytic graphite (HOPG) from acid sulphate solutions are studied using cyclic voltammetry and chronoamperometry. The electrolyte consisted of 0·001 mol dm−3 copper sulphate and 1·0 mol dm−3 sulphuric acid containing polyethylene glycol (PEG) and Cl−. It was found that the additives produce an initial inhibition of copper deposition, probably related to the adsorption. The initial deposition kinetics corresponded to a model including progressive nucleation and diffusion controlled growth. Addition of chloride ions and PEG did not change the initial nucleation of copper electrocrystallisation, but increased the nucleation rate and the number density of nuclei on the surface.

Electropolishing of titanium alloy under hydrodynamic mode

Titanium (Ti) alloys are widely used in aerospace industry due to the low density and high corrosion resistance. However, machining and polishing remain great challenges because of the hardness and chemical stability. With a home-made electrochemical machining workstation, cyclic voltammetry is performed at a wide potential range of [0 V, 20 V] to record the details of passivation and depassivation processes under a hydrodynamic mode. The results show that the thickness of viscous layer formed on the alloy surface plays a crucial effect on the electropolishing quality. The technical parameters, including the mechanical motion rate, polishing time and electrode gap, are optimized to achieve a surface roughness less than 1.9 nm, which shows a prospective application in the electrochemical machining of Ti and it alloys.

Influence of chloride and PEG on electrochemical nucleation of copper

SUMMARY The influence of chloride ions and polyethylene glycol (PEG) on the nucleation of copper on glassy carbon from acid sulphate solutions was studied by measuring potentiostatic current transients (the chronoamperometry method). It was found that instantaneous nucleation occurred at the surface for solutions without additives. The initial stage of copper nucleation did not change on addition of chloride ions, but gradually changed from progressive nucleation to instantaneous nucleation at increasing potentials in the presence of PEG. Chloride ions and PEG increase the nucleation rate and the nuclear number density of nuclei at the surface.

Studies of structure and electrocatalytic hydrogen evolution on electrodeposited Nanocrystalline Ni-Mo alloy electrodes

SUMMARY Nanocrystalline Ni-Mo alloy deposits were obtained by electrodeposition. The structures of the alloy deposits were analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD shows that Ni-Mo alloy deposit with 15·2% molybdenum exhibits (111) preferred orientation, the lattice constant is larger than that of nickel metal. The XPS results on nanocrystalline Ni-Mo alloy deposits indicate that the nickel and molybdenum of the deposits exist in the metallic state, the binding energy of the alloyed elements increase to some extent. The nanocrystalline Ni-Mo alloy deposit electrode may offer better electrocatalytic activity than the polycrystalline nickel electrode. The electrochemical impedance spectra from the nanocrystalline Ni-Mo alloy electrode indicate that hydrogen evolution in 30% (m/m) KOH is in accordance with the Volmer-Heyrovsky mechanism.

Direct electroless nickel plating on silicon surface

Direct electroless nickel plating onn-Si(100) wafers in alkaline solutions was demonstrated without any activation procedure in advance, the effect of pH and temperature of the solutions on size of metal particles in deposits was examined, and also the element contents of deposits were analyzed by energy disperse spectroscopy (EDS). The results indicated that the size of metal particles increases with increasing temperature or decreasing pH. The possible mechanism of nickel deposition onn-Si(100) was discussed in terms of semiconductor electrochemistry, and the formation of nickel seed crystal on Si was mainly attributed to the generation of atomic hydrogen by electron capture of water molecule from the semiconductor in alkaline solutions.