In the present work, porous zirconia nanostructures with different crystalline phases and structures were fabricated at low temperatures via a facile, green, and cost-effective two-step solution-phase strategy involving remarkably rapid nucleation and following a kinetically controlled hydrothermal process. ZrO2 nanostructures with different crystalline phases and structures were achieved simply by varying the concentration of the added sodium borohydride precipitant without the use of any additional surfactants and templates, and the specific surface area of ZrO2 could reach as high as 275 m2 g–1. In the synthesis process, the decomposition of NaBH4 could drive the dynamical perturbation for the reaction system through the bubble effect originating from inosculation and blast of hydrogen in situ generated, which played a crucial role in controlling the formation of ZrO2 nanostructures. Moreover, the present method could be explored for fabricating other fundamentally and technologically important metal oxides (e.g., CeO2, TiO2), indicative of good versatility.

•Highly dispersed Ru/ZnAlZr-LDH catalyst was easily prepared.•Strong interactions between Ru species and ZnAlZr-LDH were formed.•High catalytic transfer hydrogenation performance was achieved.•Cooperative effect between double-active sites was confirmed.Presently, designing high-performance catalyst systems for the sustainable production of chemicals through biomass conversions is of significant importance for large-scale practical application. As for heterogeneous catalysts, the high dispersion of active species can play a vital role in guaranteeing their superior performance. In this regard, the combination of active species with a favorable support matrix is crucial for achieving highly dispersive character of active species and the formation of cooperation between them. Herein, we first synthesized a novel ruthenium-based catalyst, Ru/Zn-Al-Zr layered double hydroxide (Ru/ZnAlZr-LDH), which was employed in the transfer hydrogenation of biomass-derived ethyl levulinate (EL) into γ-valerolactone (GVL) using 2-propanol as hydrogen donor. Extensive characterizations revealed that the interaction between Ru species and the ZnAlZr-LDH matrix helped enhance the dispersion of Ru species on the LDH and also determined the nature of electron-rich Ru species. Furthermore, a cooperative effect between double-active sites on the catalyst, e.g. a large amount of surface hydroxyl groups and highly dispersive electron-rich Ru species, was beneficial to the formation of both activated six-membered ring transition state and active ruthenium-hydride species in the course of EL transfer hydrogenation, thereby resulting in an unparalleled activity with a fastest GVL formation rate of 1250 μmol gcat−1 min−1 to date, with respect to other Zr- or Ru-based catalysts previously reported.Download full-size image

•Novel reduction-oxidation route for the synthesis of Cu/ZrO2 catalysts is established.•Metal-support interaction is responsible for the formation of surface Cu+.•Porous structure of ZrO2 support inhibits the aggregation of Cu species.•Cooperation of Cu0 and Cu+ is crucial for achieving high catalytic performance.Design and development of novel and efficient catalysts are crucial but challenging for the catalytic conversion of biomass and derivatives to fuels and chemicals. In this paper, a novel separate nucleation and aging steps assistant reduction-oxidation strategy was developed to synthesis CuO/ZrO2 complex precursor with homogeneously distributed Cu and Zr components, which can be used as an ideal precursor for the synthesis of highly dispersed Cu/ZrO2 catalyst. Characterization results revealed that homogeneous dispersion of CuO, high surface area of ZrO2 support with controlled porous structure, and strong interaction between CuO and ZrO2 in CuO/ZrO2 precursor could lead to the enhanced Cu dispersion and the formation of Cu+ active centers. The synthesized Cu/ZrO2 catalysts exhibited excellent catalytic performance (85.4% conversion of GVL and 98.0% selectivity of pentyl valerate) in the catalytic transformation of GVL to valerate esters, more efficient than that of Cu/ZrO2-CP and Cu/ZrO2-CH catalysts prepared via co-precipitation and chemisorption hydrolysis methods, respectively. The superior catalytic performance was mainly attributed to both the cooperation of Cu0 and Cu+ species and the highly dispersed surface Cu0, thereby improving the adsorption and polarization of CO bond in GVL and the following dissociation of H2 to produce active hydrogen for the hydrogenation step during the catalytic transformation of GVL. Moreover, such copper-based catalysts exhibited potential applications in the exploitation and utilization of biomass resources with significantly enhanced efficiency.Download high-res image (194KB)Download full-size image

A novel highly sensitive non-enzymatic glucose sensor was constructed based on gold nanoparticles decorated ternary Ni-Al layered double hydroxide/single-walled carbon nanotubes/graphene nanocomposite (Au/LDH-CNTs-G). The materials were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra and Raman spectra, and the sensing performance was investigated by electrochemical impedance spectroscopy, cyclic voltammetry and amperometric response. The results revealed that Au/LDH-CNTs-G nanocomposite modified glassy carbon electrode exhibited remarkable electrocatalytic performance toward glucose oxidation, with a wide linear range from 10 μM to 6.1 mM, a high sensitivity of ∼1989 μA·mM−1·cm−2 and a low detection limit of 1.0 μM based on a signal to noise ratio of 3, which was mainly attributed to the combined effects of enhanced electrical conductivity originating from three-dimensional intertwined CNTs-graphene network, good accessibility to active reaction sites from NiAl-LDH and more electron transfer passages provided by Au nanoparticles highly dispersed on the surface. What's more, as-constructed non-enzymatic sensor showed good reproducibility, repeatability, stability and anti-interference property, and was also used to practically analyze glucose concentration in human serum samples.

In this paper, graphene-supported Ni nanocatalyst (Ni/G) was prepared via self-reduction of a hybrid Ni–Al layered double hydroxide/graphene (NiAl-LDH/G) composite precursor. NiAl-LDH/G nanocomposite was assembled via a facile one-step coprecipitation route, which involved the nucleation and growth of NiAl-LDH, simultaneously accompanied by the reduction of graphene oxide without the addition of any reducing agents. The characterization results demonstrated that NiAl-LDH nanoplatelets were homogeneously dispersed on both sides of an exfoliated, structurally flexible graphene The graphene component in the precursor, serving as reducing agent, could in situ reduce Ni2+ species to Ni0 on heating under an inert atmosphere, thus facilitating the formation of highly dispersed Ni nanoparticles with a uniform size. Compared with those prepared by conventional methods, as-formed graphene-supported Ni nanocatalyst exhibited superior catalytic performance in the liquid phase selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde owing to the much higher metal dispersion and smaller size of Ni nanoparticles in the catalyst. The present finding provides a simple approach to fabricate new types of graphene-supported, metal-based heterogeneous catalysts with advanced catalytic performance.

In the present work, hybrid nanocomposites of Zn-Cr layered double hydroxide (ZnCr-LDH) and graphene were assembled successfully via a simple one-step coprecipitation method. The assembly process included the nucleation and growth of ZnCr-LDH crystals and the simultaneous reduction of GO in the absence of additional reducing agents. The experimental results revealed that ZnCr-LDH nanoplatelets with the diameter size of ∼6 nm were well dispersed on the graphene surface, and as-assembled hybrid ZnCr-LDH/graphene nanocomposites exhibited significantly improved visible-light-driven photocatalytic activity in the degradation of Rhodamine B, in comparison with pure ZnCr-LDH, which was attributable to the unique heteronanostructure of ZnCr-LDH/graphene, facilitating the efficient transportation and separation of photogenerated charges and thus continuously generating reactive oxygen species. The present work could open a new doorway for fabricating visible-light-deriven graphene-based photocatalysts for pollutant degradation via an advanced oxidation process.

In this paper, graphene-supported Ni nanocatalyst (Ni/G) was prepared via self-reduction of a hybrid Ni–Al layered double hydroxide/graphene (NiAl-LDH/G) composite precursor. NiAl-LDH/G nanocomposite was assembled via a facile one-step coprecipitation route, which involved the nucleation and growth of NiAl-LDH, simultaneously accompanied by the reduction of graphene oxide without the addition of any reducing agents. The characterization results demonstrated that NiAl-LDH nanoplatelets were homogeneously dispersed on both sides of an exfoliated, structurally flexible graphene The graphene component in the precursor, serving as reducing agent, could in situ reduce Ni2+ species to Ni0 on heating under an inert atmosphere, thus facilitating the formation of highly dispersed Ni nanoparticles with a uniform size. Compared with those prepared by conventional methods, as-formed graphene-supported Ni nanocatalyst exhibited superior catalytic performance in the liquid phase selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde owing to the much higher metal dispersion and smaller size of Ni nanoparticles in the catalyst. The present finding provides a simple approach to fabricate new types of graphene-supported, metal-based heterogeneous catalysts with advanced catalytic performance.