Xiang-Yun Guo

Cuprous oxide nanoparticles dispersed on reduced graphene oxide as an efficient electrocatalyst for oxygen reduction reaction

Cuprous oxide (Cu(2)O) nanoparticles dispersed on reduced graphene oxide (RGO) were prepared by reducing copper acetate supported on graphite oxide using diethylene glycol as both solvent and reducing agent. The Cu(2)O/RGO composite exhibits excellent catalytic activity and remarkable tolerance to methanol and CO in the oxygen reduction reaction.

Copper nanoparticles on graphene support: an efficient photocatalyst for coupling of nitroaromatics in visible light.

Copper is a low-cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible-light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C. When irradiated with natural sunlight (mean light intensity of 0.044 W cm(-2) ) at about 35 °C, 70 % of the nitrobenzene is converted and 57 % of the product is azobenzene. The electrons of the copper nanoparticles gain the energy of the incident light through a localized surface plasmon resonance effect and photoexcitation of the bound electrons. The excited energetic electrons at the surface of the copper nanoparticles facilitate the cleavage of the NO bonds in the aromatic nitro compounds. Hence, the catalyzed coupling reaction can proceed under light irradiation and moderate conditions. This study provides a green photocatalytic route for the production of azo compounds and highlights a potential application for graphene.

Enhanced Catalytic Activity for Methanol Electro‐oxidation of Uniformly Dispersed Nickel Oxide Nanoparticles—Carbon Nanotube Hybrid Materials

Highy crystalline NiO nanoparticles are uniformly grown on the walls of carbon nanotubes (CNTs) by atomic layer deposition (ALD) at moderate temperature.Their size and stoichiometry are controlled by the ALD process parameters. The obtained NiO/CNT hybrids exhibit excellent performance in the electro-oxidation of methanol.

Beaded silicon carbide nanochains via carbothermal reduction of carbonaceous silica xerogel

Novel silicon carbide nanostructures, beaded nanochains, are prepared from the carbothermal reduction of a carbonaceous silica xerogel with cetyltrimethylammonium bromide and lanthanum nitrate as additives. The nanochains consist of a stem with a diameter of about 50 nm and uniform beads with diameters of 100–200 nm. It is demonstrated that the tensile strength of an epoxy composite filled with the SiC nanochains improves significantly due to the unusual morphology of the nanochains.

NiO/SiC Nanocomposite Prepared by Atomic Layer Deposition Used as a Novel Electrocatalyst for Nonenzymatic Glucose Sensing

NiO nanoparticles are deposited onto SiC particles by atomic layer deposition (ALD). The structure of the NiO/SiC hybrid material is investigated by inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The size of the NiO nanoparticles is flexible and can be adjusted by altering the cycle number of the NiO ALD. Electrochemical measurements illustrate that NiO/SiC prepared with 600 cycles for NiO ALD exhibits the highest glucose sensing ability in alkaline electrolytes with a low detection limit of 0.32 μM (S/N = 3), high sensitivity of 2.037 mA mM(-1) cm(-2), a linear detection range from approximately 4 μM to 7.5 mM, and good stability. Its sensitivity is about 6 times of that for commercial NiO nanoparticles and NiO/SiC nanocomposites prepared by a traditional incipient wetness impregnation method. It is revealed that the superior electrochemical ability of ALD NiO/SiC is ascribed to the strong interaction between NiO and the SiC substrate and the high dispersity of NiO nanoparticles on the SiC surface. These results suggest that ALD is an effective way to deposit NiO on SiC for nonenzymatic glucose sensing.

Mesoporous NiCo2O4 Nanoplates on Three-Dimensional Graphene Foam as an Efficient Electrocatalyst for the Oxygen Reduction Reaction

Catalysts for the oxygen reduction reaction (ORR) are highly important in fuel cells and metal-air batteries. Cheap ORR catalysts with ultrahigh electrochemical activity, selectivity, and stability are extremely desirable but still remain challenging. Herein, mesoporous NiCo2O4 nanoplate (NP) arrays on three-dimensional (3D) graphene foam are shown to be a highly economical ORR catalyst. This mesoporous mixed-valence oxide can provide more electrocatalytic active sites with increased accessible surface area. In addition, graphene-foam-supported NiCo2O4 NP arrays have a 3D hierarchical porous structure, which is of great benefit to ion diffusion and electron transfer. As a result, the mesoporous NiCo2O4 NP arrays/graphene foam catalyst exhibits outstanding ORR performance with the four-electron reduction of O2 to H2O in alkaline media. Furthermore, the mesoporous catalyst shows enhanced electrocatalytic activity with a half-wave potential of 0.86 V vs RHE and better stability compared with a commercial Pt/C catalyst.

High photoelectrocatalytic performance of a MoS2–SiC hybrid structure for hydrogen evolution reaction

A flower-like MoS2–SiC hybrid structure assembled from folded MoS2–SiC nanosheets can activate hydrogen evolution at a very low overpotential (0.04 V) and produce a large cathodic current, which compares favorably with that produced by a commercial 20 wt% Pt/C catalyst.

Efficient oxygen reduction reaction using mesoporous Ni-doped Co3O4 nanowire array electrocatalysts

Herein, mesoporous Ni-doped Co3O4 nanowire (NW) arrays are reported as a highly efficient and low-cost catalyst for oxygen reduction reaction (ORR) in alkaline electrolyte. The Ni doping affords more electroactive sites and enhanced conductivity, and the mesoporous structure provides increased surface exposure, which may improve ion/electron transport and reduce charge transfer resistance. The NW arrays exhibit a high ORR activity with a four-electron transfer reaction in alkaline media, a half-wave potential of 0.86 V vs. RHE and a superior stability when compared to the commercial Pt (20 wt%)/C catalyst. Our results suggest that the mesoporous Ni-doped Co3O4 NW arrays could be a promising ORR catalyst for fuel cells and metal–air batteries.

CNT–Ni/SiC hierarchical nanostructures: preparation and their application in electrocatalytic oxidation of methanol

CNT–Ni/SiC composites with three-dimensional hierarchical nanostructures were fabricated via in situ pyrolysis of methane to grow CNTs on a novel flake-like NiO/SiC material. The NiO/SiC was prepared by hydrothermally growing Ni(OH)2 on SiC. After calcination, Ni(OH)2 was converted to porous NiO flakes. During the methane pyrolysis, NiO was in situ converted to Ni nanoparticles, which acted as the catalyst for growing CNTs. Due to the combination of Ni nanoparticles, in situ grown CNTs and the SiC support, the CNT–Ni/SiC composites exhibit excellent catalytic activity and stability in electro-oxidation of methanol. The catalytic activity shows a dependence on the pyrolysis temperature of methane, and a pyrolysis temperature of 700 °C can lead to a mass activity of 10 A mg−1 Ni, which is about 15 times higher than that of the catalyst obtained from methane pyrolysis at 500 °C and about 4000 times higher than that of the original NiO/SiC catalyst.

Visible light-induced selective photocatalytic aerobic oxidation of amines into imines on Cu/graphene

Graphene can stabilize metallic copper nanoparticles and enable them to exhibit excellent photocatalytic activity for aerobic oxidation of various primary and secondary amines into the corresponding imines. The copper nanoparticles stabilized on graphene absorb the energy of visible light via localized surface plasmon resonance, and produce energetic hot electrons that activate the reactants adsorbed on the surface of copper nanoparticles. The formation of imines involves selective oxygenation of amines to aldehydes and subsequent condensation with amines to form imines.