Mingshan Zhu

Graphene Oxide Enwrapped Ag/AgX (X = Br, Cl) Nanocomposite as a Highly Efficient Visible-Light Plasmonic Photocatalyst

In this paper, we have reported that well-defined graphene oxide (GO) enwrapped Ag/AgX (X = Br, Cl) nanocomposites, which are composed of Ag/AgX nanoparticles and gauze-like GO nanosheets, could be facilely fabricated via a water/oil system. We have shown that thus-synthesized GO-based hybrid nanocomposites could be used as a stable plasmonic photocatalyst for the photodegradation of methyl orange (MO) pollutant under visible-light irradiation. Compared with the corresponding bare Ag/AgX nanospecies, the GO-involved nanocomposites (Ag/AgX/GO) display distinctly enhanced photocatalytic activities. The hybridization of Ag/AgX with GO nanosheets causes the nice adsorptive capacity of Ag/AgX/GO to MO molecules, the smaller size of the Ag/AgX nanoparticles in Ag/AgX/GO, the facilitated charge transfer, and the suppressed recombination of electron-hole pairs in Ag/AgX/GO. It is suggested that these multifactors, resulting from the hybridization of GO, contribute to the enhanced photocatalytic performance observed from Ag/AgX/GO. The investigation likely opens up new possibilities for the development of original yet highly efficient and stable GO-based plasmonic photocatalysts that utilize visible light as an energy source.

Ag/AgBr/Graphene Oxide Nanocomposite Synthesized via Oil/Water and Water/Oil Microemulsions: A Comparison of Sunlight Energized Plasmonic Photocatalytic Activity

In this article, we report that Ag/AgBr nanostructures and the corresponding graphene oxide (GO) hybridized nanocomposite, Ag/AgBr/GO, could be facilely synthesized by means of a surfactant-assisted assembly protocol, where an oil/water microemulsion is used as the synthesis medium. We show that thus-produced nanomaterials could be used as highly efficient and stable plasmonic photocatalysts for the photodegradation of methyl orange (MO) pollutant under sunlight irradiation. Compared with the bare Ag/AgBr nanospecies, Ag/AgBr/GO displays distinctly enhanced photocatalytic activity. More importantly, the as-prepared nanostructures exhibit higher photocatalytic activity than that of the corresponding Ag/AgBr-based nanomaterials synthesized viaa water/oil microemulsion and than that of the corresponding Ag/AgCl-based nanospecies synthesized by an oil/water microemulsion. An explanation has been proposed for these interesting findings. Our results suggest that thus-manufactured Ag/AgBr/GO plasmonic photocatalysts are promising alternatives to the traditional UV light or visible-light driven photocatalysts.

Surfactant Assistance in Improvement of Photocatalytic Hydrogen Production with the Porphyrin Noncovalently Functionalized Graphene Nanocomposite

In this paper, a 5,10,15,20-tetrakis(4-(hydroxyl)phenyl) porphyrin (TPPH) noncovalently functionalized reduced graphene oxide (RGO) nanohybrid has been facilely synthesized by immobilizing TPPH on RGO nanosheets. This nanohybrid was characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and UV-vis spectra, which demonstrated that the TPPH molecule was attached on the surface of the graphene nanosheet. The results of fluorescence quenching and photocurrent enhancement of TPPH-RGO exhibit that the fast electrons transfer from photoexcited TPPH molecules to RGO sheets. Compared with bare TPPH or RGO functional Pt nanoparticles, the TPPH-sensitized RGO loaded with Pt nanoparticles shows remarkable enhanced photocatalytic activity under UV-vis light irradiation. The superior electron-accepting and electron-transporting properties of graphene greatly accelerate the electron transfer from excited TPPH to Pt catalysts, which promote the photocatalytic activity for hydrogen evolution. More importantly, with the assistance of cetyltrimethylammonium bromide (CTAB) surfactant, the catalytic activity and stability is further improved owing to aggregation prevention of TPPH-RGO nanocomposites. Our investigation might not only initiate new opportunities for the development of a facile synthesis yet highly efficient photoinduced hydrogen evolution system (composed of organic dye functionalized graphene) but also pave a new avenue for constructing graphene-based matericals with enhanced catalytic performance and stability under surfactant assistance.

Clean method for the synthesis of reduced graphene oxide-supported PtPd alloys with high electrocatalytic activity for ethanol oxidation in alkaline medium.

In this article, a clean method for the synthesis of PtPd/reduced graphene oxide (RGO) catalysts with different Pt/Pd ratios is reported in which no additional components such as external energy (e.g., high temperature or high pressure), surfactants, or stabilizing agents are required. The obtained catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), induced coupled plasma atomic emission spectroscopy (ICP-AES), and electrochemical measurements. The HRTEM measurements showed that all of the metallic nanoparticles (NPs) exhibited well-defined crystalline structures. The composition of these Pt-Pd/RGO catalysts can be easily controlled by adjusting the molar ratio of the Pt and Pd precursors. Both cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that bimetallic PtPd catalysts have superior catalytic activity for the ethanol oxidation reaction compared to the monometallic Pt or Pd catalyst, with the best performance found with the PtPd (1:3)/RGO catalyst. The present study may open a new approach for the synthesis of PtPd alloy catalysts, which is expected to have promising applications in fuel cells.

Metal-Free Photocatalyst for H2 Evolution in Visible to Near-Infrared Region: Black Phosphorus/Graphitic Carbon Nitride

In the drive toward green and sustainable chemistry, exploring efficient and stable metal-free photocatalysts with broadband solar absorption from the UV to near-infrared region for the photoreduction of water to H2 remains a big challenge. To this end, a binary nanohybrid (BP/CN) of two-dimensional (2D) black phosphorus (BP) and graphitic carbon nitride (CN) was designed and used as a metal-free photocatalyst for the first time. During irradiation of BP/CN in water with >420 and >780 nm light, solid H2 gas was generated, respectively. Owing to the interfacial interaction between BP and CN, efficient charge transfer occurred, thereby enhancing the photocatalytic performance. The efficient charge-trapping and transfer processes were thoroughly investigated with time-resolved diffuse reflectance spectroscopic measurement. The present results show that BP/CN is a metal-free photocatalyst for artificial photosynthesis and renewable energy conversion.

Sunlight-driven plasmonic photocatalysts based on Ag/AgCl nanostructures synthesized via an oil-in-water medium: enhanced catalytic performance by morphology selection

Herein, we have demonstrated that spherical and quasi-cubic Ag/AgCl-based plasmonic photocatalysts could be controllably synthesized by means of a one-pot surfactant-assisted method, wherein an oil-in-water system is employed as synthesis medium. We have found that thus-produced nanostructures can display stable photocatalytic performance for the photodegradation of Methyl Orange (MO) pollutant when energized with sunlight or visible light, where morphology dependent and enhanced photocatalytic activity could be realized. Compared with the Ag/AgCl nanospheres, their quasi-cubic counterparts exhibit much higher photocatalytic activity, which could be further enhanced upon hybridization with graphene oxide (GO). Moreover, in contrast to the spherical Ag/AgCl nanospecies formulated via a water-in-oil medium, those synthesized through the oil-in-water system display higher photocatalytic activity. On the basis of our experimental facts, a plausible explanation has been proposed for these significant findings. The investigation has not only one-pot controllably produced sunlight energized Ag/AgCl-based plasmonic photocatalysts with morphology dependent catalytic performance, but also essentially increased their catalytic activity.

Template-Free Synthesis of Cube-like Ag/AgCl Nanostructures via a Direct-Precipitation Protocol: Highly Efficient Sunlight-Driven Plasmonic Photocatalysts

In this paper, we report that cube-like Ag/AgCl nanostructures could be facilely fabricated in a one-pot manner through a direct-precipitation protocol under ambient conditions, wherein no additional issues such as external energy (e.g., high temperature or high pressure), surfactants, or reducing agents are required. In terms of using sodium chloride (NaCl) as chlorine source and silver acetate (CH₃COOAg) as silver source, it is disclosed that simply by adding an aqueous solution of NaCl into an aqueous solution of CH₃COOAg, Ag/AgCl nanostructures with a cube-like geometry, could be successfully formulated. We show that thus-formulated cube-like Ag/AgCl nanospecies could be used as high-performance yet durable visible-light-driven or sunlight-driven plasmonic photocatalysts for the photodegradation of methyl orange (MO) and 4-chlorophenol (4-CP) pollutants. Compared with the commercially available P25-TiO₂, and the Ag/AgCl nanospheres previously fabricated via a surfactant-assisted method, our current cube-like Ag/AgCl nanostructures could exhibit much higher photocatalytic performance. Our template free protocol might open up new and varied opportunities for an easy synthesis of cube-like Ag/AgCl-based high-performance sunlight-driven plasmonic photocatalysts for organic pollutant elimination.

High-Performance Visible-Light-Driven Plasmonic Photocatalysts Ag/AgCl with Controlled Size and Shape Using Graphene Oxide as Capping Agent and Catalyst Promoter

We report herein that Ag/AgCl-based plasmonic photocatalysts with controlled size and shape could be easily formulated by a one-pot approach via a precipitation reaction between AgNO3 or Ag(NH3)2NO3 and NaCl. It is found that near-spherical and cube-like Ag/AgCl nanoarchitectures of 500 nm could be fabricated at lower and higher temperature, respectively. Fascinatingly, when graphene oxide (GO) nanosheets are introduced into the synthesis medium, the size of the formulated near-spherical and cube-like nanostructures, Ag/AgCl/GO, could be 2.5 and 5 times reduced to ca. 200 and 100 nm, respectively, when AgNO3 and Ag(NH3)2NO3 are employed as the silver source. The series of our Ag/AgCl-based nanostructures could be used as visible-light-driven plasmonic photocatalysts for the photodegradation of methyl orange pollutants, wherein the cube-like Ag/AgCl/GO nanoarchitectures of 100 nm display the highest catalytic activity. It is disclosed that the synergistic effect of size, shape, and GO nanosheets plays an important role for their boosted photocatalytic performances. The investigation reveals that GO nanosheets work not only as a capping agent for a controllable fabrication of Ag/AgCl nanostructures, but also as catalyst promoter during the photocatalytic performances, leading to an enhanced catalytic activity. Our unique GO-assisted method likely paves a facile avenue and initiates new opportunities for the exploration of GO-hybridized high-performance catalysts.

Au/La2Ti2O7 Nanostructures Sensitized with Black Phosphorus for Plasmon-Enhanced Photocatalytic Hydrogen Production in Visible and Near-Infrared Light

Efficient utilization of solar energy is a high-priority target and the search for suitable materials as photocatalysts that not only can harvest the broad wavelength of solar light, from UV to near-infrared (NIR) region, but also can achieve high and efficient solar-to-hydrogen conversion is one of the most challenging missions. Herein, using Au/La2 Ti2 O7 (BP-Au/LTO) sensitized with black phosphorus (BP), a broadband solar response photocatalyst was designed and used as efficient photocatalyst for H2 production. The optimum H2 production rates of BP-Au/LTO were about 0.74 and 0.30 mmol g-1  h-1 at wavelengths longer than 420 nm and 780 nm, respectively. The broad absorption of BP and plasmonic Au contribute to the enhanced photocatalytic activity in the visible and NIR light regions. Time-resolved diffuse reflectance spectroscopy revealed efficient interfacial electron transfer from excited BP and Au to LTO which is in accordance with the observed high photoactivities.

Highly efficient visible-light-driven plasmonic photocatalysts based on graphene oxide-hybridized one-dimensional Ag/AgCl heteroarchitectures

In this paper, we report that one-dimensional (1D) Ag/AgCl nanostructures could be facilely fabricated by means of an oxidation-chloridization process, wherein prefabricated 1D Ag nanowires are employed as a template. Graphene oxide (GO)-hybridized 1D Ag/AgCl nanocomposites, Ag/AgCl/GO, could also be easily formulated when GO nanosheets are involved during the oxidation-chloridization procedure. We find that compared with the parent plain 1D Ag nanowires, commercially available P25-TiO2, and spherical Ag/AgCl nanospecies, the as-produced 1D Ag/AgCl nanostructures could be used as high-performance visible-light-driven plasmonic photocatalysts for the photodegradation of organic pollutants. Moreover, the 1D Ag/AgCl/GO nanocomposites exhibit enhanced photocatalytic activity compared with the corresponding 1D Ag/AgCl nanostructures. Our experimental facts indicate that the cooperative or synergistic effects between the intrinsic morphological features of the 1D nanostructures, which facilitates an efficient directional electron transport and suppresses the scattering of the free electrons, and the advantages brought out by GO nanosheets, which favors a nice adsorption of methyl orange (MO) molecules and an efficient charge separation, conjointly contribute to the enhanced photocatalytic performance of the 1D Ag/AgCl/GO nanocomposites. This work might initiate new and more varied opportunities for the development of visible-light-driven high-performance plasmonic photocatalysts for the photodegradation of organic pollutants.