Shen Lin

The synergistic effect of graphene and polyoxometalates enhanced electrocatalytic activities of Pt-{PEI-GNs/[PMo12O40]3−}n composite films regarding methanol oxidation

The {PEI-GNs/PMo12}n composite films are prepared by an LBL electrostatic assembly technique, and their uniform and homogeneous traits have been verified by UV-vis and cyclic voltammetry. The {PEI-GNs/PMo12}n composite films are used as a novel catalyst support for electro-deposition of Pt particles in situ. Pt particles immobilizing on the surface of {PEI-GNs/PMo12}n composite films were confirmed by XPS, EDX, XRD and FE-SEM. The interesting seashell-like Pt micro–nano-clusters can be obtained when {2PEI-GNs/PMo12} composite films are used as catalyst supports. Pt-{PEI-GNs/PMo12}n composite films present good electrocatalytic activity regarding methanol oxidation and improved tolerance of CO. These results indicate that poly(ethyleneimine) functionalized graphene (PEI-GNs) preserves the superior electric conductivities of graphene sheets in the composite films, and the introduction of electroactive [PMo12O40]3− (PMo12) into the composite films helps to convert intermediate species CO into CO2 from the Pt nanoparticles. The synergistic effect of PEI-GNs and PMo12 remarkably enhanced the electrocatalytic activity and stability regarding methanol oxidation.

One-step microwave synthesis of Pt (Pd)/Cu2O/GNs composites and their electro-photo-synergistic catalytic properties for methanol oxidation

A facile one-pot method was used to synthesize Pt/Cu2O/GNs and Pd/Cu2O/GNs composites. Pt or Pd nanoparticles are deposited onto graphene sheets (GNs) and Cu2O via synchronous reduction of K2PtCl4 (K2PdCl4), Cu(OH)2 and graphene oxide (GO) with glucose as a reducing agent under microwave irradiation. The formation of Cu2O promotes the nucleation of Pt(0) or Pd(0) particles and favors more complete reduction of PtCl42− or PdCl42−. Catalytic properties of as-prepared composites for methanol oxidation reaction (MOR) were evaluated by cyclic voltammetry (CV), chronoamperometry, COads stripping voltammetry and electrochemical impedance spectrum (EIS). Electrochemical experiments showed that Pt/Cu2O/GNs and Pd/Cu2O/GNs had much higher catalytic activity and stability for MOR and better resistance to CO poisoning compared with the commercially available Johnson Matthey 20% Pt/C catalyst (Pt/C-JM) and Sigma-Aldrich 20% Pd/C catalyst (Pd/C-SA). Especially under the UV irradiation, the total peak current density and catalytic stability of Pt/Cu2O/GNs and Pd/Cu2O/GNs drastically increase, which may result from the synergistic effect between the electro-catalytic and photo-catalytic properties. In brief, the cooperation among Pt (Pd), Cu2O and GNs promotes remarkably the catalytic performance for MOR on Pt/Cu2O/GNs and Pd/Cu2O/GNs either without light or with UV irradiation.

In situ electro-deposition of Pt micro-nano clusters on the surface of {[PMo12O40]3−/PAMAM}n multilayer composite films and their electrocatalytic activities regarding methanol oxidation

The {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films are prepared by LBL electrostatic assembly technique, and their uniform and homogeneous traits have been verified by cyclic voltammetry. The {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films with PAMAM as the outmost layer, having an open structure and exhibiting good penetrability for the solvent molecules at low pH, are used as matrices for electro-deposition of Pt micro-nano clusters in situ. X-ray photoelectron spectroscopy (XPS) analysis and field emission scanning electron microscope (FE-SEM) characterization show that the unique Pt micro-nano clusters with flower-like structure have been immobilized on the surface of {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films. The morphologies of Pt micro-nano clusters are influenced by electro-deposition conditions such as deposition potential, deposition time, and the number of layers of {[PMo(12)O(40)](3-)/PAMAM}(n) multilayer films. Pt(-clusters)-{PMo(12)/PAMAM}(3) composite films demonstrate good electrocatalytic activities regarding methanol oxidation and improved tolerance of CO.

Preparation of Pt/{PDDA-GN/PSS-GN}n multilayer films and their electrocatalytic activity regarding methanol oxidation

The stable aqueous dispersion solutions of polymer-modified graphene were prepared by reduction with hydrazine hydrate in situ from exfoliated graphite oxides in the presence of poly (diallyldimethylammonium chloride) (PDDA) and poly(sodium 4-styrenesulfonate) (PSS), respectively. The multilayer films consisting of PDDA-GN and PSS-GN were fabricated on the substrate by layer-by-layer self-assembly technique and characterized by ultraviolet-visible spectroscopy (UV-vis). The multilayer films were used as a novel catalyst support for electrodeposition of Pt nanoparticle clusters in situ. X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FE-SEM), and X-ray diffraction (XRD) analysis demonstrated that Pt particles had been immobilized on the surface of {PDDA-GN/PSS-GN}(n) multilayer films. Cyclic voltammetry and chronoamperometric curves were used to study electrocatalytic activity of Pt/{PDDA-GN/PSS-GN}(n) multilayer films regarding methanol oxidation. The results indicated good electrocatalytic activity of the titled multilayer composites toward methanol oxidation in the 0.5 M H(2)SO(4).

Palladium(II)/Polyoxometalate‐Catalyzed Direct Alkenylation of Benzofurans under Atmospheric Dioxygen

An efficient and selective C2 alkenylation of benzofurans was performed by using Pd(OAc)2 combined with a catalytic amount of 11‐molybdovanadophosphoric acid (H4PMo11VO40) under an atmosphere of dioxygen. N‐Acetylglycine (Ac‐Gly‐OH) was observed to be an effective additive for the olefination reaction.