•An ionic liquid (IL) etching strategy was developed to synthesize CeO2 nanocubes.•The CuxO/CeO2 nanocube catalysts were obtained via depositing CuOx clusters on CeO2 nanocubes.•The interaction between CuxO and CeO2 can induce the reduction of Cu2+ to Cu+ to provide more active CO adsorption sites.•The oxygen vacancies on the surface of CuxO/CeO2 catalysts play an important role in enhancing CO-PROX reaction.In this paper, a facile strategy by etching CeO2 spheres pretreated by different concentrations of H2SO4 or NaOH solution with an ionic liquid (IL) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) under hydrothermal condition was developed to achieve CeO2 nanocubes. By depositing CuxO clusters on CeO2 nanocubes via a deposition−precipitation method, CuxO/CeO2 nanocube catalysts loading with different amounts of CuxO clusters were synthesized and the CuxO clusters were highly dispersed onto the surface of CeO2 nanocubes. The Raman spectroscopy, H2-TPR, XPS, and DRIFTS results reveal that there is a strong interaction between CuxO and CeO2. Among these CuxO/CeO2 catalysts, the 10CuCe-2OH-ILs, which was obtained via immersing CeO2 spheres using 2 M NaOH, and subsequently being etched by ILs, and then loading ∼10% of copper, exhibits the optimal catalytic performances and stability. The catalytic activity of different catalysts increases in the order of 10CuCe-ILs < 10CuCe-1H-ILs < 10CuCe-0.1OH-ILs < 10CuCe-5OH-ILs < 10CuCe-2OH-ILs. The result is in agreement with the order of the surface oxygen vacancy concentration, reducibility and Cu+ content, suggesting that the interaction between CuxO species and surface oxygen vacancies of these CuxO/CeO2 catalysts plays an important role for CO preferential oxidation in H2-rich gases.A facile strategy by etching CeO2 spheres pretreated by different concentrations of H2SO4 or NaOH solution with an ionic liquid (IL) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) was developed to achieve CeO2 nanocubes. CuxO/CeO2 nanocube catalysts were obtained via a deposition−precipitation method for CO-PROX reaction.Download full-size image

•Hybrid of Ni3N/N-RGO catalysts are synthesized by using a two-step method.•The catalysts manifest superior catalytic activity towards the ORR.•High activities are attributed to enhanced electron density and synergistic effects.Novel nickel nitride (Ni3N) nanoparticles supported on nitrogen-doped reduced graphene oxide nanosheets (N-RGOs) are synthesized via a facile strategy including hydrothermal and subsequent calcination methods, in which the reduced graphene oxide nanosheets (RGOs) are simultaneously doped with nitrogen species. By varying the content of the RGOs, a series of Ni3N/N-RGO nanocomposites are obtained. The Ni3N/N-RGO-30% hybrid nanocomposite exhibits superior catalytic activity towards oxygen reduction reaction (ORR) under alkaline condition (0.1 M KOH). Furthermore, this hybrid catalyst also demonstrates high tolerance to methanol poisoning. The RGO containing rich N confers the nanocomposite with large specific surface area and high electronic conduction ability, which can enhance the catalytic efficiency of Ni3N nanoparticles. The enhanced catalytic activity can be attributed to the synergistic effect between Ni3N and nitrogen doped reduced graphene oxide. In addition, the sufficient contact between Ni3N nanoparticles and the N-RGO nanosheets simultaneously promotes good nanoparticle dispersion and provides a consecutive activity sites to accelerate electron transport continuously, which further enhance the ORR performance. The Ni3N/N-RGO may be further an ideal candidate as efficient and inexpensive noble metal-free ORR electrocatalyst in fuel cells.Download high-res image (243KB)Download full-size imageWe report a facile hydrothermal synthetic strategy to fabricate novel hierarchical of Ni3N/N-RGO nanocomposites with various morphologies and structures. It’s worth mentioning that the nitrogen atoms are simultaneous doped into the Ni3N and reduced graphene oxide, which can provide more multi-active sites for these nanocomposites and exhibit enhanced catalytic performance towards the ORR. The Ni3N/N-RGO-30% exhibits superior activity and high tolerance to methanol poisoning towards oxygen reduction reaction (ORR), which are ascribed to the synergetic effect between Ni3N and nitrogen doped reduced graphene oxide.

Rational design of inexpensive, highly active, and long-term stable non-precious metal electrocatalysts for oxygen reduction reaction (ORR) is of significant importance for large-scale applications of fuel cells in practice. In this paper, we report, for the first time, the construction of 2D layered mesoporous transition metal-nitrogen-doped carbon/nitrogen-doped graphene (meso-M-N-C/N-G, M = Fe, Co, and Ni) electrocatalysts using 4,4-bipyridine as the nitrogen and carbon source and mesoporous KIT-6/N-G generated by in situ formation of KIT-6 on graphene nanosheets as a template. The meso-Fe-N-C/N-G electrocatalyst showed super electrocatalytic performance for ORR. Excitingly, its catalytic activity and durability were superior to those of Pt/C, making it a good candidate as an ORR electrocatalyst in fuel cells. The results suggested that the outstanding electrocatalytic performance of the electrocatalysts could be attributed to the unique mesoporous structure, high surface area, ultrasmall size of Fe or FeOx nanocrystals embedded in 2D layered N-G nanosheets, excellent electron transportation, homogeneous distribution of high-density pyridinic N and graphitic N, graphitic C, and abundant metal active sites (Fe-Nx). The synthesis approach can be used as a versatile route toward the construction of various 2D layered graphene-based mesoporous materials.

It is of great importance to exploit and design efficient and low-cost alternatives to platinum-based electrocatalysts for the hydrogen evolution reaction (HER). In this work, we report novel well-defined 0D/2D heterojunctions of uniform molybdenum carbide-tungsten carbide quantum dots ((Mo2C)x–(WC)1−x–QDs, ∼3–5 nm)/N-doped graphene (NG) nanosheets with a two-dimensional layered structure obtained via a nanocasting method using KIT-6/graphene (G) as a template. By controlling the molar ratio of the Mo and W precursors, (Mo2C)x–(WC)1−x–QDs (0 < x < 1)/NG nanohybrids with different Mo/W molar ratios can be obtained, which exhibit superior activity in the HER to individual Mo2C/NG and WC/NG nanohybrids. The superior activity in the HER may be attributed to redistribution of the valence electrons of Mo and W elements, nitrogen-coordinating sites, and highly dispersed Mo2C–WC nanocrystals, as well as strong coupling between Mo2C–WC nanocrystals and NG. Excitingly, the optimal electrocatalyst, namely, (Mo2C)0.34–(WC)0.32/NG, exhibited low overpotentials (100 and 93 mV) to achieve a cathodic current density of 10 mA cm−2, small Tafel slopes (53 and 53 mV dec−1), and high exchange current densities (0.419 and 0.804 mA cm−2) in acidic and alkaline media, respectively. More importantly, it also displayed excellent long-term durability for 25 h of stable catalytic current at different pH values. This work is expected to provide a feasible route for the fabrication of 0D/2D earth-abundant nanocomposites for the HER.

The rational design of non-noble materials as low-cost, highly efficient, and durable catalysts to improve the oxygen reduction reaction is extremely urgent and challenging. The oxygen reduction reaction is a kinetically sluggish process that greatly affects the energy conversion efficiency. In this paper, novel hierarchical heteroatoms-co-doped Fe2M/graphene (M = P, N) nanocomposites were developed by a facile strategy, including hydrothermal and subsequent calcination methods. The thermal treatment of an ionic liquid and thiourea not only supplied heteroatom sources but also promoted the formation of iron phosphide and iron nitride and enhanced their catalytic performances. The electrochemical results indicated that the as-obtained hybrid catalysts manifested enhanced electrocatalytic activity toward the oxygen reduction reaction owing to the strong synergistic effects. The high content of heteroatoms distributed on the surface and interface of the hybrids and the density functional theory calculations suggested that Fe–N–C, Fe–P–C, and Fe–S–C multiple active surface sites were formed at the hybrids interfaces. Moreover, these results demonstrated that heteroatom-doped catalysts could effectively form a charge-transfer channel and thus modify the charge distribution in the hybrids interfaces. The as-prepared heteroatoms-doped Fe2M/graphene hybrids would be developed into highly efficient catalysts as ideal alternatives for noble metal catalysts in practical applications.

Driven by the need of high catalytic performance and low cost Pt-based catalysts for methanol oxidation (MOR) and oxygen reduction (ORR) reactions, we developed a highly active nitrogen species-decorated Pt–Ni–N catalyst with tunable architectures and facets toward high catalytic activity. The synthetic procedure was conducted by Ni2+-assisted morphology and facet transformation from nanoflowers (NFs) (111) to nanoparticles (NPs) (220) and simultaneous optimization of both hierarchical structure and active surface sites. It is found that the adsorption of nitrogen species plays critical roles in determining both facet control of the Pt–Ni–N hierarchical structure and energetic activation of the catalytic reaction. Decoration of surface nitrogen species can effectually improve the relative content and electronic density of Pt0, leading to formation of a hierarchical structure and significantly improved catalytic activity toward both MOR and ORR compared with Pt–Ni and Pt–N, as well as the commercial Pt/C catalysts, indicating a new strategy to obtain highly efficient catalysts. Moreover, the results demonstrate that the catalytic enhancement is mainly due to the synergistic electronic effects among Pt, Ni, and N species.

The development of bifunctional electrocatalysts for both the methanol oxidation reaction (MOR) at the anode and the oxygen reduction reaction (ORR) at the cathode is urgently required for promoting electrochemical energy conversion and lowering the cost of fuel cells. The surface electron configuration, correlated to the surface elemental composition and the valence state of an electrocatalyst plays crucial roles in achieving bifunctionality and efficient electrocatalysis. In this study, we demonstrate the achievement of bifunctional Pt–Fe alloy electrocatalysts for effectively catalyzing both the MOR and ORR by tailoring their surface electron configuration via a synthetic strategy employing a Wattecs parallel autoclave system (WPAS), which allows the alteration of reaction atmospheres and operating conditions during the synthetic process, in contrast to a normal hydrothermal method. The optimal Pt–Fe alloy electrocatalyst displayed remarkably enhanced ORR electrocatalytic performance with a half-potential (E1/2) of 0.9 V (vs. Ag/AgCl), together with robust stability (3000 cycles), in the ORR in a 0.1 M HClO4 solution and exhibited excellent catalytic performance in the MOR with a mass activity of 1.82 A mg−1, which is 7.9 times higher than that of commercial 20% Pt/C (0.23 A mg−1). These Pt–Fe alloy electrocatalysts also possessed long-term stability and the ability to tolerate CO intermediates and hold great significance for widespread applications in the field of renewable energy owing to their low cost and superior bifunctionality for both the MOR and ORR. The variability of the surface electron configuration that arose from the purposive modulation of the chemical composition and valence state of the surface of the Pt–Fe alloy electrocatalysts accounted for the increase in electrocatalytic performance and the achievement of bifunctional catalysis in both the MOR and ORR.

We reported the design of a core–shell Cu@PtCu electrocatalyst consisting of dendritic PtCu alloy branches assembling on Cu core nanocrystals. The Cu@PtCu electrocatalyst shows superior electrocatalytic performance toward a methanol oxidation reaction. Its specific activity and mass activity can reach 3.56 mA cm−2 and 1568 mA mgPt−1, which are 4.8 and 7.1 times higher than those of a commercial 20% Pt/C catalyst.

•The 2D layered meso-MoO2/rGO electrode materials has been synthesized via a novel nanocasting method.•The 2D layered meso-MoO2/rGO composite combining graphene with MoO2 and endowing it mesoporous structure.•The composite can offer a support for anchoring KIT-6 template and work as a highly conductive matrix.•The meso-MoO2/rGO composite can minimize diffusion lengths for Li+ and e−, and prevent the volume effect effectively.Transition metal oxides are great promising anode materials with much higher theoretical electrochemical capacities for lithium ion battery compared with the commercialized carbon materials while serious capacity fading and poor cycle stability caused by large volume change and sluggish kinetics must be addressed for their practical application. Herein, we demonstrated a novel strategy to synthesize 2D layered mesoporous-MoO2/graphene (meso-MoO2/rGO) electrode materials using KIT-6/rGO as a template and ammonium molybdate as a precursor via a nanocasting method. By combining graphene with MoO2 and endowing it mesoporous structure, 2D layered meso-MoO2/rGO electrode materials are expected to show superior electrical conductivity, structured flexibility, and chemical stability, which may provide uninhibited conducting pathways for fast charge transfer and transport between oxide nanoparticles and graphene. In addition, mesoporous MoO2 is also anticipated to optimize Li+ transport in pore walls and fast electrolyte transport within highly ordered mesopores. As a result, meso-MoO2/rGO electrode materials possess an ordered mesoporous structure with a superior electrochemical performance. The electrochemical performances were examined using galvanostatical charge-discharge, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) techniques. Benefiting from the combining effects of mesoporous MoO2 and 2D layered graphene, meso-MoO2/rGO electrode materials alleviate the volume effect and give an enhanced discharge and charge capacity and robust cycle stability. The meso-MoO2/rGO composite delivers the first discharge capacity of 1160.6 mA h g−1 and its reversible capacity is 801 mA h g−1 after 50 cycles, making it promising for potential uses as high performance anode materials in lithium-ion battery.Download high-res image (305KB)Download full-size image

Hierarchical carbon and nitrogen adsorbed PtNiCo nanocomposites with different morphologies and facets were successfully synthesized via a solvothermal method and showed high electrochemical activity and long-term stability towards the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Electrochemical results indicated that the (220) facet-terminated PtNiCo@C–N nanocubes manifest superior electro-catalytic activity compared to other morphologies and facets as well as the commercial state-of-the-art Pt/C catalyst (20%). The surface carbon and nitrogen atoms, multiple active surface sites, and synergistic electronic effects of various elements contribute to the high electro-catalytic performance of the electrocatalysts. It is worth mentioning that the carbon and nitrogen atoms were simultaneously adsorbed onto the surface of the catalysts, which can provide more multiple active sites for these nanocomposites. In order to demonstrate this result, a solvent ligand exchange method was explored to demonstrate that these multiple active sites on the surface of the catalysts can be exchanged into n-hexane solution, and thus the catalytic activity dramatically decreased. The present work highlights the carbon and nitrogen adsorbed PtNiCo@C–N nanocomposites as highly active catalysts for polymer electrolyte membrane fuel cells (PEMFCs).

A universal strategy was developed for fabrication of a highly active and durable precious-metal-free mesoporous Mo2C/graphene (m-Mo2C/G) electrocatalyst with a two-dimensional layered structural feature via a nanocasting method using glucose as a carbon source and an in-stiu assembled mesoporous KIT-6/graphene (KIT-6/G) as a template. The m-Mo2C/G catalyst exhibits high catalytic activity and excellent durability for hydrogen evolution reaction (HER) over a wide pH range, which displays a small onset potential of 8 mV, owerpotential (η10) for driving a cathodic current density of 10 mA·cm–2 of 135 mV, a Tafel slope of 58 mV·dec–1, and an exchange current density of 6.31 × 10–2 mA·cm–2 in acidic media and an onset potential of of 41 mV, η10 of 128 mV, Tafel slope of 56 mV·dec–1, and an exchange current density of 4.09 × 10–2 mA·cm–2 in alkaline media, respectively. Furthermore, such an m-Mo2C/G electrocatalyst also gives about 100% Faradaic yield and shows excellent durability during 3000 cycles of a long-term test, and the catalytic current remains stable over 20 h at fixed overpotentials, making it a great potential application prospect for energy issues.

We constructed a series of two-dimensional (2D) layered mesoporous mono- and binary-transition-metal nitride/graphene nanocomposites (TMN/G, TM = Ti, Cr, W, Mo, TiCr, TiW, and TiMo) via an efficient and versatile nanocasting strategy for the first time. The 2D layered mesoporous TMN/G is constituted of small TMN nanoparticles composited with graphene nanosheets and has a large surface area with high porosity. Through decoration with well-dispersed Pt nanoparticles, 2D layered mesoporous Pt/TMN/G catalysts can be obtained that display excellent catalytic activity and stability for methanol electro-oxidation reactions (MOR) and oxygen reduction reactions (ORR) in both acidic and alkaline media. The 2D layered mesoporous binary-Pt/TMN/G catalysts possess catalytic activity superior to that of mono-Pt/TMN/G, graphene free Pt/TMN, Pt/G, and Pt/C catalysts. Encouragingly, the 2D layered mesoporous Pt/Ti0.5Cr0.5N/G catalyst exhibits the best electrocatalytic performance for both MOR and ORR. The outstanding electrocatalytic performance of the Pt/Ti0.5Cr0.5N/G catalyst is rooted in its large surface area, high porosity, strong interaction among Pt, Ti0.5Cr0.5N, and graphene, an excellent electron transfer property facilitated by N-doped graphene, and the small size of Pt and Ti0.5Cr0.5N nanocrystals. The outstanding catalytic performance provides the 2D layered mesoporous Pt/Ti0.5Cr0.5N/G catalyst with a wide range of application prospects in direct methanol fuel cells in both acidic and alkaline media. The synthetic method may be available for constructing other 2D layered mesoporous metal nitrides, carbides, and phosphides.

•A novel hollow mesoporous ternary @M-TiN/N-G/Pt electrocatalysts were synthesized.•The @M-TiN/N-G/Pt electrocatalysts displayed outstanding activity and stability toward MOR and ORR.•The activity and stability of @M-TiN/N-G/Pt electrocatalysts were higher than Pt/TiN, @M-TiN/Pt, and Pt/C catalysts.•The excellent electrocatalytic performance rooted in its unique configuration.•Several reasons were proposed to explain the enhanced electrocatalytic performance of @M-TiN/N-G/Pt.A novel hollow mesoporous TiN/N-graphene (N-G) hybrid architecture (@M-TiN/N-G) composed of N-doped graphene wrapped mesoporous TiN nanoparticle shells was constructed for the first time. It can be used as an efficient support for creating a highly efficient ternary @M-TiN/N-G/Pt electrocatalyst with superior catalytic activity and stability for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR) through decorating well-dispersed Pt nanoparticles on @M-TiN/N-G surface. By optimizing the content of N-G in catalysts, the @M-TiN/N-G/Pt catalysts display superior catalytic activity and stability toward MOR and ORR to traditional Pt/C and graphene-free Pt/TiN and @M-TiN/Pt catalysts. The various characterization results reveal that the outstanding electrocatalytic performance of @M-TiN/N-G/Pt catalyst roots in its large surface area, high porosity, strong interaction among Pt, TiN, and N-G, excellent electron transfer property facilitated by N-doped graphene, and small size of Pt and TiN nanocrystals. The synthetic approach may be available for constructing other graphene based hollow metal nitrides, carbides, and phosphides for various electrocatalytic applications.Download high-res image (209KB)Download full-size image

The exposure of the crystallographic facets of CeO2 nanocrystals may alter their surface structure and composition, leading to significant discrepancies in their reactivity with respect to catalyzing different reactions. In this paper, a facile strategy of etching hollow CeO2 spheres (@CeO2) with a fluorine-containing ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), under hydrothermal conditions was developed to achieve surface-fluorinated @CeO2 nanoparticles with exposed active high-energy facets, which were further assembled in situ into @CeO2 nanoparticle assemblies. The IL, [Bmim][BF4], is believed to play an important role in determining the formation of CeO2 nanoparticles, and the mild release of fluorine species from [Bmim][BF4] may account for the surface-fluorination and the exposure of active high-energy facets of CeO2. The CeO2 nanoparticle assemblies are ideal model materials for studying crystal facet-dependent catalytic behavior. By loading well-dispersed Au nanoparticles via a sol-impregnation method, @CeO2/Au nanoparticle assemblies were achieved, which showed an enhanced catalytic performance for benzyl alcohol aerobic oxidation. In comparison with @CeO2/Au nanoparticle assemblies obtained by etching @CeO2 spheres with other fluorine-containing agents, NH4BF4, NaBF4, and NH4F, under identical reaction conditions, @CeO2/Au nanoparticle assemblies achieved by etching with [Bmim][BF4] exhibited the highest catalytic activity for benzyl alcohol aerobic oxidation. The surface-fluorination and the exposure of active high-energy facets of CeO2 nanoparticles are believed to be responsible for the enhancement of their catalytic activity. This methodology provides a robust strategy to create CeO2 materials with the active high-energy facets exposed and afford model materials for investigating crystal facet-dependent catalytic behavior, which currently represents an exciting issue in the nanocatalysis community.

A facile hydrothermal etching process was developed to synthesize TiO2/Ag nanocubes for enhanced photocatalytic application. The synthesis was carried out by chemically etching hollow @TiO2 spheres in the presence of an AgF or AgF/NaF solution under hydrothermal conditions. Utilizing F− as a morphology-directing agent and Ag+ as an Ag source during the etching process, TiO2 nanocubes can be easily formed with their active high-energy facets exposed and Ag nanoparticles can be in situ deposited simultaneously on the surface of the TiO2 nanocubes to generate hybrid TiO2/Ag nanocubes. The resulting TiO2/Ag nanocubes were well controlled with Ag nanoparticles uniformly distributed on the surface of the TiO2 nanocubes. The morphologies of TiO2/Ag can be altered from ellipsoidal to cubic shapes depending on the amounts of AgF or AgF/NaF used for chemical etching. Due to the exposure of the active high-energy facets of TiO2 and the uniform deposition of Ag nanoparticles, the obtained TiO2/Ag nanocubes showed superior catalytic performance for the photocatalytic degradation of rhodamine B under visible-light radiation. It is proposed that the surface plasmon resonance effect arisen from Ag nanoparticles on TiO2 nanocubes can effectively enhance the visible-light driven photocatalytic properties of TiO2/Ag photocatalysts. Meanwhile, due to the etching of F ions during the synthetic process, the morphology variation of TiO2 from spherical to cubic shapes may be beneficial to the exposure of high energy {001} facets, which is liable to produce more electron–hole pairs in the photocatalytic process, and electron–hole pairs can combine with OH− to produce large amounts of hydroxyl radicals, eventually accelerating the decomposition of the organic dye.

We report the creation of highly efficient, dual-heterostructured catalysts consisting of magnetic Fe3O4 cores and CeO2 shells coated with noble metal nanoparticles (NMNPs) (Pt, Pd and Pt–Pd nanoparticles). These intriguing dual-heterostructural features that favor reactant diffusion and exposure of active sites can enhance synergistic catalytic effects between the NMNPs and CeO2 nanoparticles. The synergistic catalytic effect and redox effect features between Fe3O4 and CeO2 are beneficial for superior catalytic and electrochemical performance. Impressively, the resultant Fe3O4@CeO2/Pd (3 wt%) and Fe3O4@CeO2/Pt (20 wt%) catalysts manifest superior catalytic efficiency and electrocatalytic reactivity toward the reduction of 4-nitrophenol and oxidation of methanol in alkaline solution, demonstrating the significance of the dual heterostructure of these recyclable catalysts. This synthetic strategy provides a new methodology for the fabrication of other high-performance and multifunctional catalysts, which would be very useful in various catalytic reactions.

•Pd@Pt bimetallic are synthesized by using different capping agents.•A facile method to remove these capping agents is reported.•The structure and morphology can be retained, enhancing the number of active sites.•The catalysts manifest superior catalytic activity towards the methanol oxidation.A series of well-dispersed bimetallic Pd@Pt nanodendrites uniformly supported on XC-72 carbon black are fabricated by using different capping agents. These capping agents are essential for the branched morphology control. However, the surfactant adsorbed on the nanodendrites surface blocks the access of reactant molecules to the active surface sites, and the catalytic activities of these bimetallic nanodendrites are significantly restricted. Herein, a facile reflux procedure to effectively remove the capping agent molecules without significantly affecting their sizes is reported for activating supported nanocatalysts. More significantly, the structure and morphology of the nanodendrites can also be retained, enhancing the numbers of active surface sites, catalytic activity and stability toward methanol and ethanol electro-oxidation reactions. The as-obtained hot water reflux-treated Pd@Pt/C catalyst manifests superior catalytic activity and stability both in terms of surface and mass specific activities, as compared to the untreated catalysts and the commercial Pt/C and Pd/C catalysts. We anticipate that this effective and facile removal method has more general applicability to highly active nanocatalysts prepared with various surfactants, and should lead to improvements in environmental protection and energy production.Well-dispersed bimetallic Pd@Pt nanodendrites uniformly supported on XC-72 carbon nanospheres, are successfully synthesized by using different capping agents. The as-obtained reflux-treated Pd@Pt/C catalysts manifest superior catalytic activity and stability both in terms of surface and mass specific activities toward the methanol and ethanol oxidation reaction, as compared to the un-treated samples and commercial Pt/C and Pd/C catalysts.

Porous Pt/CeO2–Co3O4 catalysts are fabricated via thermal decomposition of cerium nitrate hexahydrate and cobaltous acetate tetrahydrate precursors using polystyrene sphere colloidal crystals as templates followed by Pt impregnation. The obtained catalysts possess well-defined macroporous skeletons and mesoporous walls, adjustable chemical compositions, and varied surface elemental states. The macro- and meso-porous Pt/CeO2–Co3O4 catalysts show superior catalytic performance to traditional powder Pt/CeO2–Co3O4 catalysts for CO preferential oxidation in H2-rich gases. The redox activity and the valence state of the macro- and meso-porous Pt/CeO2–Co3O4 catalysts are largely varied depending on their chemical compositions and further cause the strong synergy between Pt, CeO2 and Co3O4, which accounts for the improvement of catalytic performance. Meanwhile, the macro- and meso-porous structure in Pt/CeO2–Co3O4 catalysts is conducive to the diffusion of reactants and products, thus enhancing the catalytic performance simultaneously.

•A facile method is developed for synthesis of CdTe@SiO2/Ag nanocomposites.•The CdTe@SiO2/Ag nanocomposites show efficient fluorescence.•The CdTe@SiO2/Ag nanocomposites are explored as alternative fluorescent markers for latent fingerprint detection.•The CdTe@SiO2/Ag nanocomposites provide better resolution, high sensitivity, and antibacterial activity.•The CdTe@SiO2/Ag nanocomposites may find potential application in forensic science.This paper developed a facile method to synthesize CdTe@SiO2/Ag nanocomposites by coupling uniform Ag nanoparticles on core–shell CdTe@SiO2 quantum dots via simple impregnation of CdTe@SiO2 functionalized with amino groups in Ag nanoparticle sols. The obtained CdTe@SiO2/Ag nanocomposites show efficient fluorescence and effective antibacterial activities. Besides, because of the existence of SiO2, the CdTe@SiO2/Ag nanocomposites manifest strong adhesive affinity and chemical stability, allowing the long-term preservation of fluorescence and affording affinity with latent fingerprints. Thus, the CdTe@SiO2/Ag nanocomposites are explored as alternative fluorescent markers for latent fingerprint detection to provide better resolution, high sensitivity, and antibacterial activities. Meanwhile, the CdTe@SiO2/Ag nanocomposites may be used as alternative fluorescent markers for enhanced latent fingerprint detection on a variety of object surfaces in criminal science for individual identification.

•Three dimensionally ordered cobalt or iron doped ceria-copper catalysts are synthesized.•The catalysts possess the superior catalytic performance for CO proficiential oxidation.•The catalytic performance can be modulated in a wide operation temperature window.Three dimensionally ordered (3DOM) copper-ceria based catalysts (CeO2–CuO, CeO2–CuO–Fe2O3, and CeO2–CuO–Co3O4) with diverse Ce/Cu atomic ratios and different doping amounts of Fe2O3 and Co3O4 are synthesized via a precursor thermal decomposition-assisted colloidal crystal templating method. The as-obtained CeO2–CuO, CeO2–CuO–Fe2O3 and CeO2–CuO–Co3O4 catalysts possess three dimensionally ordered macroporous structures. And their particle sizes, chemical compositions, and surface elemental states are investigated according to the variations of Ce/Cu atomic ratios and doping amounts of Fe2O3 and Co3O4. The catalytic performance of CO preferential oxidation in H2-rich gases over 3DOM CeO2–CuO, CeO2–CuO–Fe2O3, and CeO2–CuO–Co3O4 catalysts are mainly relevant to their particle sizes, chemical compositions, surface states, and synergetic interactions between different components. By modulating the Ce/Cu atomic ratios and the doping amounts of Fe2O3 and Co3O4, the superior catalytic performance of 3DOM CeO2–CuO catalysts with high CO conversion, CO2 selectivity and longer-term stability in a wide operation temperature window is achieved. This synthetic strategy provides a new methodology for the fabrication of 3DOM structured highly efficient catalysts, which would be very useful in the actual working conditions for proton exchange membrane fuel cells and water-gas shift reactions.

Rational design of the hierarchical architecture of a material with well controlled functionality is crucially important for improving its properties. In this paper, we present the general strategies for rationally designing and constructing three types of hierarchical Pd integrated TiO2 double-shell architectures, i.e. yolk–double-shell TiO2 architecture (Pd@TiO2/Pd@TiO2) with yolk-type Pd nanoparticles residing inside the central cavity of the hollow TiO2 structure; ultrafine Pd nanoparticles homogenously dispersed on both the external and internal surfaces of the inner TiO2 shell; and double-shell TiO2 architecture (@TiO2/Pd@TiO2) with Pd nanoparticles solely loaded on the external surface of the inner TiO2 shell, and double-shell TiO2 architecture (@TiO2@Pd@TiO2) with Pd nanoparticles dispersed in the interlayer space of double TiO2 shells, via newly developed Pd2+ ion-diffusion and Pd sol impregnation methodologies. These architectures are well controlled in structure, size, morphology, and configuration with Pd nanoparticles existing in various locations. Owing to the variable synergistic effects arising from the location discrepancies of Pd nanoparticle in the architectures, they exhibit remarkable variations in catalytic activity. In particular, different from previously reported yolk–shell structures, the obtained yolk–double-shell Pd@TiO2/Pd@TiO2 architecture, which is revealed for the first time, possesses a uniform hierarchical structure, narrow size distribution, and good monodispersibility, and it creates two Pd–TiO2 interfaces on the external and internal surfaces of the inner TiO2 shell, leading to the strongest synergistic effect of Pd nanoparticles with TiO2 shell. Furthermore, the interlayer chamber between the double TiO2 shells connecting with the central cavity of the hollow TiO2 structure through the mesoporous TiO2 wall forms a nanoreactor for enriching the reactants and preventing the deletion of Pd nanoparticles during the reaction, thus greatly accelerating the reaction speed. Owing to its structural features, yolk–double-shell Pd@TiO2/Pd@TiO2 architecture exhibits extremely high catalytic performance on the Suzuki–Miyaura coupling reaction. The synthetic methodologies are robust for fabricating double-shell architectures with various configurations for applications such as in catalysis, drug delivery, and medicine release. The obtained double-shell architectures may be used as novel catalyst systems with highly efficient catalytic performance for other catalytic reactions.

A novel mesoporous “shell-in-shell” structured nanocatalyst (@Pd/meso-TiO2/Pd@meso-SiO2) with large surface area, enhanced synergy, and improved catalytic performance is created for catalyzing Suzuki–Miyaura coupling and 4-nitrophenol reduction reactions.

Three dimensionally ordered macroporous (3DOM) Au/CeO2 catalysts were synthesized via a thermal decomposition-assisted colloidal crystal templating method following different synthetic procedures using citric acid and oxalic acid as chelating ligands and CeCl3 and Ce(NO3)3 as cerium salt precursors. All 3DOM Au/CeO2 catalysts possess well-defined 3DOM skeletons composed of well-crystallized CeO2 nanoparticles, based on the different synthetic procedures, the 3DOM Au/CeO2 catalysts show variations in surface elemental compositions, particle sizes of CeO2, macroporous and mesoporous structures, and valence states of Au. The mesoporous walls with nanopores ∼3–4 nm on 3DOM Au/CeO2 skeletons can be created when using Ce(NO3)3 as precursor. The catalytic performance of 3DOM Au/CeO2 catalysts for CO preferential oxidation in H2-rich gases was systematically investigated. The catalytic performance is closely correlated to surface elemental compositions, particle sizes of CeO2, macroporous and mesoporous structures, and valence states of Au due to the different synthetic procedures. The 3DOM Au/CeO2 catalysts prepared using oxalic acid as chelating ligand and Ce(NO3)3 as cerium salt precursor show the highest catalytic activity for CO preferential oxidation in H2-rich gases with 90.1% CO conversion and 59.9% CO2 selectivity at 50 °C, and 88.3% CO conversion and 59.3% CO2 selectivity at 80 °C, respectively. The obtained 3DOM Au/CeO2 catalysts may be of importance for guiding the design of efficient catalysts with desired porous structures that are potentially applicable in polymer electrolyte membrane fuel cells.

We develop a facile layer-by-layer deposition process to create bi-functional Fe3O4@SiO2@Gd2O3:Yb,Er nanostructures composed of magnetic Fe3O4 cores, variable SiO2 mid-layers, and up-converting Gd2O3 shells. The synthetic process is well-controlled and the obtained Fe3O4@SiO2@Gd2O3:Yb,Er nanoparticles show relative monodispersity and exhibit tunable magnetic and up-conversion luminescence depending on the thickness of SiO2 mid-layers. The influences of SiO2 mid-buffer-layers on morphology, magnetism, and up-conversion luminescence are well addressed. The obtained bi-functional Fe3O4@SiO2@Gd2O3:Yb,Er nanoparticles may be potentially applicable in magnetic, fluorescent, and biological applications. The synthetic route may be employed for fabricating other multifunctional nanostructures.

Eu3+-doped tetragonal and hexagonal YPO4 nanocrystals with different phase structures and morphologies were successfully synthesized by a solvothermal method. It was found that the pH value is a crucial factor in determining the phase structures and their morphologies of YPO4:Eu nanocrystals. The crystal structure and the properties of the Eu3+-doped YPO4 nanocrystals were characterized by XRD, SEM, TEM, UV–Vis spectroscopy.

We report the design and realization of double shelled @CeO2/M@M/TiO2 (M = Au and/or Pd) nanospheres with dual noble metal nanoparticles encapsulated in metal oxide shells via a layer-by-layer deposition process followed by an alkali etching method. The resulting nanospheres possess uniform sizes, variable shell components and thicknesses, adjustable noble metal nanoparticles encapsulated, regulable chamber spaces between the two shells, and good structural stability, which can be used as unique microreactors with extremely high catalytic activity and stability in the Suzuki–Miyaura coupling reaction, benzyl aerobic alcohol oxidation, and 4-nitrophenol reduction reaction due to their structural features with multiple interactions and strong synergistic effects between the noble metal nanoparticles and metal oxide shells, and less depletion of catalytic active species. The designed double shelled hollow @CeO2/M@M/TiO2 nanocatalysts can be used as novel catalyst systems with highly efficient catalytic performance for various catalytic reactions depending on their shell components and noble metal nanoparticles encapsulated. The synthetic strategy provides a new methodology to design high-performance and multifunctional nanocatalysts.

We report the creation of highly efficient sandwich-like structured nanocatalysts consisting of magnetic Fe3O4 cores, porous SiO2 and CeO2 shells and coated with noble metal nanoparticles (NMNPs). The nanocatalysts possess uniform sizes, variable shell compositions and thicknesses, adjustable noble metal nanoparticle coatings, tunable morphologies and good structural stability, and can be used as unique catalysts with extremely high catalytic activity and stability for the 4-nitrophenol reduction reaction due to their structural features with multiple interactions and strong synergistic effects between the noble metal nanoparticles and the cerium oxide shells. The designed double shelled Fe3O4@SiO2@CeO2/M nanocatalysts can be used as novel catalyst systems with highly efficient catalytic performance for various catalytic reactions depending on their shell components and noble nanoparticle coating. The synthetic strategy provides a new methodology to design high-performance and recyclable nanocatalysts.

A novel magnetic double-shell Fe3O4@TiO2/Au@Pd@TiO2 microsphere composed of a Fe3O4 core and double TiO2 shells with Au and Pd nanoparticles encapsulated is created. The microsphere can be used as a highly efficient reusable catalyst with superior catalytic activity and stability and magnetic separable capability in reduction of 4-nitrophenol.

Novel hollow mesoporous @M/CeO2 (M = Au, Pd, and Au–Pd) nanospheres are created. The nanospheres can be used as effective nanoreactors with superior catalytic activity and stability for reduction of 4-nitrophenol due to their hollow mesoporous structural features.

Cubic α- and hexagonal β-phase lanthanide luminescent NaYF4:Eu3+/Tb3+ nanostructures with diverse morphologies were successfully synthesized via a mild solvothermal method. The effects of the synthetic parameters on the crystal phase structure, size and morphology of NaYF4:Eu3+/Tb3+ nanostructures were systematically investigated. By modifying the synthetic parameters, the crystal phase structure, size and morphology were well controlled, and the phase transition from cubic α- to hexagonal β- can be easily realized. Furthermore, the morphology evolution is revealed, and the surfactant modulating formation mechanisms with diverse morphologies was proposed. The photoluminescence properties were found to be in close correlation with their composition, phase structure and morphology. NaYF4:Eu3+/Tb3+ nanostructures possessing unique morphologies and highly efficient luminescence may find potential applications in optoelectronics, sensors and biolabels.

Fe/Fe3O4 nano-cubes and nano-octahedrons have been successfully synthesized by employing a facile solvothermal method at 180 °C in the presence of ethylene glycol (EG). Well-defined assembly of uniform Fe/Fe3O4 with an average size of 400 nm could be obtained without a size-selection process. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy were used to characterize the structure and morphology of the products. The magnetic properties of Fe/Fe3O4 nanocomposite were measured by using a vibrating sample magnetometer. The result of magnetic characterization reveals that the magnetic polyhedrons exhibit a ferromagnetic behavior and possess high saturation magnetization. It is expected that these magnetic polyhedron with uniform size would have potential applications in recording media and electrode materials.

CdTe–montmorillonite (CdTe–MMT) nanocomposites are synthesized by in situ intercalation of CdTe quantum dots (QDs) into a sodium MMT clay matrix via an ion exchange process following a low-temperature solution synthetic approach. Due to the confinement of CdTe QDs in the layered structure of the sodium MMT clay matrix, the resulting CdTe–MMT nanocomposites possess very stable chemical properties in air and show interesting tunable highly efficient UV radiation-dependent photoluminescence. The obtained CdTe–MMT nanocomposites overcome the oxidation problem of pure CdTe QD powders in air, which may result in weakening of photoluminescence. Due to their chemical stability, enhanced adhesive property, easy preparation, low cost, and unique photoluminescence, the CdTe–MMT nanocomposites are used as alternative fluorescent labeling markers for enhanced latent fingerprint detection on a variety of object surfaces in forensic science for individual identification. In contrast with those detected with commercially available fluorescent labeling marks, fingerprints detected with CdTe–MMT nanocomposites can be well-defined in terms of finger ridge details without background staining, resulting in good definition for enhanced detection. The obtained CdTe–MMT nanocomposites may find potential application in forensic science for individual identification.

An ionic liquid (IL) (1-butyl-3-methylimidazolium tetrafluoroborate)-based route was introduced into the synthesis of novel spherical NaYF4 nanoclusters with the assistance of a microwave-accelerated reaction system. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected area electron diffraction (SAED), energy-dispersive X-ray spectroscopy (EDS) and upconversion (UC) luminescence spectroscopy were used to characterize the obtained products. Interestingly, these spherical NaYF4 nanoclusters with diameters ranging from 200 to 430 nm are formed by the self-assembly of small nanoparticles. The diameters of the nanoclusters could be easily tuned just by changing the amounts of the precursors. By conducting the control experiments with different ILs or precursors, it is proven that the ILs have played key roles, such as the solvents for the reaction, the absorbents of microwave irradiation, and the major fluorine sources for the formation of the NaYF4 nanocrystals. The UC luminescence properties of the Ln3+ codoped NaYF4 were measured, and the results indicate that the nanoclusters obtained in BmimBF4 exhibit excellent UC properties. Since this IL-based and microwave-accelerated procedure is efficient and environmentally benign, we believe that this method may have some potential applications in the synthesis of other nanomaterials.

Three-dimensionally ordered macroporous (3DOM) Au/CeO2–Co3O4 catalysts with well-defined macroporous skeletons and mesoporous walls were created via a precursor thermal decomposition-assisted colloidal crystal templating method, and their catalytic performance for CO preferential oxidation in H2-rich gases was systematically investigated. The results showed that the 3DOM Au/CeO2–Co3O4 catalysts possessed well-defined 3DOM skeletons composed of well-crystallized CeO2 and Co3O4 nanoparticles and mesoporous walls with nanopores ∼3–4 nm. Their catalytic performance was closely correlated to their compositions, phase structures, porous architectures, surface elemental compositions, and valence states. In comparison with the Au supported CeO2 or Ce3O4 catalysts previously reported, the 3DOM Au/CeO2–Co3O4 catalysts showed superior catalytic conversion, selectivity, and stability—in particular, longer-term stability—for CO preferential oxidation in H2-rich gases, making them potentially applicable in polymer electrolyte membrane fuel cells.Graphical abstractThree-dimensionally ordered macroporous (3DOM) Au/CeO2–Co3O4 catalysts with well-defined macroporous skeletons and mesoporous walls were created, and the improved CO PROX in H2-rich gases with superior catalytic conversion, selectivity, and stability was realized in such 3DOM Au/CeO2–Co3O4 catalysts.Download high-res image (230KB)Download full-size imageHighlights► Three-dimensionally ordered macroporous Au/CeO2–Co3O4 catalysts were created. ► They show enhanced CO preferential oxidation in H2-rich gases. ► Their superior catalytic is attributed to the three-dimensionally macroporous skeleton with mesoporous walls.

Three-dimensionally ordered macroporous (3DOM) Au/CeO2 catalysts with controlled pore sizes are successfully created via a colloidal crystal template method, and their enhanced catalytic performance for formaldehyde oxidation is systematically investigated for the first time in this paper. The resulting Au/CeO2 catalysts possess well-defined 3DOM structures with adjustable pore sizes from 80 to 280 nm, having interconnected networks of spherical voids. Due to the uniform macroporous structures leading to good distribution of catalytic species of Au nanoparticles with less aggregation, the 3DOM Au/CeO2 catalysts are expected to have enhanced capability for formaldehyde catalytic oxidation. The formaldehyde oxidation tests reveal that the 3DOM Au/CeO2 catalysts exhibit superior catalytic activity with 100% formaldehyde conversion at ∼75 °C, a much lower temperature than previously reported powder Au/CeO2 catalysts. The superior performance of 3DOM Au/CeO2 catalysts for formaldehyde oxidation makes them potentially applicable to in-door formaldehyde decontamination and industrial catalysis.

Realization of anionic nonmetal doping and high energy crystal facet exposure in TiO2 photocatalysts has been proven to be an effective approach for significantly improving their photocatalytic performance. A facile strategy of ionic liquid assisted etching chemistry by simply hydrothermally etching hollow TiO2 spheres composed of TiO2 nanoparticles with an ionic liquid of 1-butyl-3-methylimidazolium tetrafluoroborate without any other additives is developed to create highly active anatase TiO2 nanocubes and TiO2 nanocube assemblies. With this one-pot ionic liquid assisted etching process, the surface-fluorination and nitridation and high energy {001} crystal facets exposure can be readily realized simultaneously. Compared with the benchmark materials of P25 and TiO2 nanostructures with other hierarchical architectures of hollow spheres, flaky spheres, and spindles synthesized by hydrothermally etching hollow TiO2 spheres with nonionic liquid of NH4F, the TiO2 nanocubes and TiO2 nanocube assemblies used as efficient photocatalysts show super high photocatalytic activity for degradation of methylene blue, methyl orange, and rhodamine B, due to their surface-fluorination and nitridation and high energy crystal facet exposure. The ionic liquid assisted etching chemistry is facile and robust and may be a general strategy for synthesizing other metal oxides with high energy crystal facets and surface doping for improving photocatalytic activity.

Rational design of inexpensive, highly active, and long-term stable non-precious metal electrocatalysts for oxygen reduction reaction (ORR) is of significant importance for large-scale applications of fuel cells in practice. In this paper, we report, for the first time, the construction of 2D layered mesoporous transition metal-nitrogen-doped carbon/nitrogen-doped graphene (meso-M-N-C/N-G, M = Fe, Co, and Ni) electrocatalysts using 4,4-bipyridine as the nitrogen and carbon source and mesoporous KIT-6/N-G generated by in situ formation of KIT-6 on graphene nanosheets as a template. The meso-Fe-N-C/N-G electrocatalyst showed super electrocatalytic performance for ORR. Excitingly, its catalytic activity and durability were superior to those of Pt/C, making it a good candidate as an ORR electrocatalyst in fuel cells. The results suggested that the outstanding electrocatalytic performance of the electrocatalysts could be attributed to the unique mesoporous structure, high surface area, ultrasmall size of Fe or FeOx nanocrystals embedded in 2D layered N-G nanosheets, excellent electron transportation, homogeneous distribution of high-density pyridinic N and graphitic N, graphitic C, and abundant metal active sites (Fe-Nx). The synthesis approach can be used as a versatile route toward the construction of various 2D layered graphene-based mesoporous materials.

We reported the design of a core–shell Cu@PtCu electrocatalyst consisting of dendritic PtCu alloy branches assembling on Cu core nanocrystals. The Cu@PtCu electrocatalyst shows superior electrocatalytic performance toward a methanol oxidation reaction. Its specific activity and mass activity can reach 3.56 mA cm−2 and 1568 mA mgPt−1, which are 4.8 and 7.1 times higher than those of a commercial 20% Pt/C catalyst.

Porous Pt/CeO2–Co3O4 catalysts are fabricated via thermal decomposition of cerium nitrate hexahydrate and cobaltous acetate tetrahydrate precursors using polystyrene sphere colloidal crystals as templates followed by Pt impregnation. The obtained catalysts possess well-defined macroporous skeletons and mesoporous walls, adjustable chemical compositions, and varied surface elemental states. The macro- and meso-porous Pt/CeO2–Co3O4 catalysts show superior catalytic performance to traditional powder Pt/CeO2–Co3O4 catalysts for CO preferential oxidation in H2-rich gases. The redox activity and the valence state of the macro- and meso-porous Pt/CeO2–Co3O4 catalysts are largely varied depending on their chemical compositions and further cause the strong synergy between Pt, CeO2 and Co3O4, which accounts for the improvement of catalytic performance. Meanwhile, the macro- and meso-porous structure in Pt/CeO2–Co3O4 catalysts is conducive to the diffusion of reactants and products, thus enhancing the catalytic performance simultaneously.

We report the creation of highly efficient, dual-heterostructured catalysts consisting of magnetic Fe3O4 cores and CeO2 shells coated with noble metal nanoparticles (NMNPs) (Pt, Pd and Pt–Pd nanoparticles). These intriguing dual-heterostructural features that favor reactant diffusion and exposure of active sites can enhance synergistic catalytic effects between the NMNPs and CeO2 nanoparticles. The synergistic catalytic effect and redox effect features between Fe3O4 and CeO2 are beneficial for superior catalytic and electrochemical performance. Impressively, the resultant Fe3O4@CeO2/Pd (3 wt%) and Fe3O4@CeO2/Pt (20 wt%) catalysts manifest superior catalytic efficiency and electrocatalytic reactivity toward the reduction of 4-nitrophenol and oxidation of methanol in alkaline solution, demonstrating the significance of the dual heterostructure of these recyclable catalysts. This synthetic strategy provides a new methodology for the fabrication of other high-performance and multifunctional catalysts, which would be very useful in various catalytic reactions.

Hierarchical carbon and nitrogen adsorbed PtNiCo nanocomposites with different morphologies and facets were successfully synthesized via a solvothermal method and showed high electrochemical activity and long-term stability towards the methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). Electrochemical results indicated that the (220) facet-terminated PtNiCo@C–N nanocubes manifest superior electro-catalytic activity compared to other morphologies and facets as well as the commercial state-of-the-art Pt/C catalyst (20%). The surface carbon and nitrogen atoms, multiple active surface sites, and synergistic electronic effects of various elements contribute to the high electro-catalytic performance of the electrocatalysts. It is worth mentioning that the carbon and nitrogen atoms were simultaneously adsorbed onto the surface of the catalysts, which can provide more multiple active sites for these nanocomposites. In order to demonstrate this result, a solvent ligand exchange method was explored to demonstrate that these multiple active sites on the surface of the catalysts can be exchanged into n-hexane solution, and thus the catalytic activity dramatically decreased. The present work highlights the carbon and nitrogen adsorbed PtNiCo@C–N nanocomposites as highly active catalysts for polymer electrolyte membrane fuel cells (PEMFCs).

We report the creation of highly efficient sandwich-like structured nanocatalysts consisting of magnetic Fe3O4 cores, porous SiO2 and CeO2 shells and coated with noble metal nanoparticles (NMNPs). The nanocatalysts possess uniform sizes, variable shell compositions and thicknesses, adjustable noble metal nanoparticle coatings, tunable morphologies and good structural stability, and can be used as unique catalysts with extremely high catalytic activity and stability for the 4-nitrophenol reduction reaction due to their structural features with multiple interactions and strong synergistic effects between the noble metal nanoparticles and the cerium oxide shells. The designed double shelled Fe3O4@SiO2@CeO2/M nanocatalysts can be used as novel catalyst systems with highly efficient catalytic performance for various catalytic reactions depending on their shell components and noble nanoparticle coating. The synthetic strategy provides a new methodology to design high-performance and recyclable nanocatalysts.

A novel magnetic double-shell Fe3O4@TiO2/Au@Pd@TiO2 microsphere composed of a Fe3O4 core and double TiO2 shells with Au and Pd nanoparticles encapsulated is created. The microsphere can be used as a highly efficient reusable catalyst with superior catalytic activity and stability and magnetic separable capability in reduction of 4-nitrophenol.

Novel hollow mesoporous @M/CeO2 (M = Au, Pd, and Au–Pd) nanospheres are created. The nanospheres can be used as effective nanoreactors with superior catalytic activity and stability for reduction of 4-nitrophenol due to their hollow mesoporous structural features.

A novel mesoporous “shell-in-shell” structured nanocatalyst (@Pd/meso-TiO2/Pd@meso-SiO2) with large surface area, enhanced synergy, and improved catalytic performance is created for catalyzing Suzuki–Miyaura coupling and 4-nitrophenol reduction reactions.