Xiaofeng Zhang

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.

Electrochemical growth of octahedral Fe3O4 with high activity and stability toward the oxygen reduction reaction

Octahedral Fe3O4 crystals were prepared by a facile potentiostatic deposition approach. The as-prepared Fe3O4 exhibits high electrocatalytic activity toward the oxygen reduction reaction (ORR) and excellent stability. The unique octahedral structure provides a high density of active sites and facilitates the ORR via a dominant pathway of oxygen reduction to hydroxide.

Green synthesis of PdCu supported on graphene/polyoxometalate LBL films for high-performance formic acid oxidation

PdCu alloy nanoparticles (with sizes of ca. 4.5 nm) have been synthesized by a one-step electrochemical process on composite films constructed from functionalized graphene (GN) and H3PMo12O40 (PMo12) by LBL assembly. The as-prepared hybrid displays enhanced eletrocatalytic activity and extended durability towards formic acid oxidation in an acid media.

Controlled synthesis of Pt/CS/PW12-GNs composite as an anodic electrocatalyst for direct methanol fuel cells

Controlled assembly in aqueous solution was used to synthesize the well-organized Pt/CS/PW12-GNs composite. By the aid of linear cationic polysaccharide chitosan, 2-D distribution worm-like Pt nanoparticles with their length and width of 15–20 and 3–4xa0nm, respectively, were formed on the surface of CS/PW12-GNs using HCOOH as a reducing agent at room temperature. The introduction of CS leads to well dispersion of worm-like Pt nanoparticles, the electroactivity of H3PW12O40 (PW12) alleviates CO poisoning toward Pt particles, and graphene nanosheets (GNs) ensure excellent electrical conductivity of the composites. The combined action among different components results in significantly enhanced catalytic activity of Pt/CS/PW12-GNs toward methanol oxidation and better tolerance of CO. The as-synthesized Pt/CS/PW12-GNs exhibit the forward peak current density of 445xa0mAxa0mg−1, which is much higher than that (220xa0mAxa0mg−1) for Pt/C-JM (the commercially available Johnson Matthey Hispec4000 catalyst, simplified as Pt/C-JM) and some recently reported Pt/graphene-based nanomaterials. The construction of 2-D distribution worm-like Pt nanoparticles and facile wet chemical synthesis strategy provide a promising way to develop superior performance electrocatalysts for direct methanol fuel cells applications.

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.

Facile synthesis of Pd/PDDA-GN/PMo11Co composite and its enhanced catalytic performance for formic acid oxidation

A novel Pd-based catalyst, Pd/poly(diallyldimethylammonium chloride) functionalized graphene (PDDA-GN)/transition-metal-substituted polyoxometalate H7PMo11CoO40·xH2O (PMo11Co), for direct formic acid fuel cells (DFAFC) has been prepared by a layer by layer (LBL) electrostatic assembly method combined with electro-deposition of Pd particles in situ. The morphology, particle size and composition of the as-prepared Pd/PDDA-GN/PMo11Co composite were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results reveal that Pd particles are uniformly deposited on the surface of PDDA-GN/PMo11Co. Electrochemical analysis shows that the Pd/PDDA-GN/PMo11Co composite exhibits higher electrocatalytic activity, better electrochemical stability, and higher resistance to CO poisoning than the Pd/PDDA-GN/PMo12 and Pd/C catalysts for the formic acid oxidation reaction (FAOR). The current density of the anodic peak at the Pd/PDDA-GN/PMo12 modified electrode in the formic acid oxidation process is up to 639.3 mA mg−1, which is 4.2 times that of the Pd/C and 1.2 times that of the Pd/PDDA-GN/PMo12. The experimental investigations indicate that PDDA-GN as a support preserves superior electric conductivity of graphene sheets of the composite, and the introduction of electroactive PMo11Co into the composite contributes to convert intermediate species CO into CO2. The synergistic effects of PDDA-GN and PMo11Co remarkably enhance the electrocatalytic activity and stability of nano-Pd regarding formic acid oxidation.

Effects of Interaction between PAMAM and Polyoxometalates on Catalytic Performance for Oxidation of Isobutyraldehyde

G1.0 (Generation1.), G2.0, G3.0, G4.0 polyamidoamine (PAMAM) dendrimers-supported Na5CoII(H2O)PW11O39 (PW11Co) were prepared by co-precipitation method. They were characterized by UV-Vis, XPS, XRD, and TEM. It is suggested that as the generation of the PAMAM dendrimers increased, the interaction between PW11Co and PAMAM dendrimer enhanced and the particle size of PW11Co decreased. The catalytic activities for the oxidation of isobutyraldehyde (IBA) to isobutyric acid (IBAc) by PW11Co-PAMAM(G1.0, G2.0, G3.0, G4.0) were examined.