A series of highly active Pt–TiO2 catalysts have been prepared by impregnation methods via different reduction processes and used for catalytic decomposition of benzene. The oxidized and reduced Pt–TiO2 catalysts exhibit apparent differences in physical/chemical features (e.g. particle size, chemical state, and electronic property of Pt nanoparticles, and surface oxygen) and catalytic activities for benzene oxidation. Nearly 100 % benzene conversion is achieved on Pt–TiO2 catalysts obtained by the sodium citrate (C6H5Na3O7·2H2O, Na3Ct) reduction at approximate 160 °C. Metallic Pt nanoparticles have strong capacity for oxygen activation, and the negative charges and rich chemisorbed oxygen on the surface of metallic Pt nanoparticles are probably responsible for their high catalytic activities for benzene oxidation.

A solution-based approach has been developed for the synthesis of hollow or yolk–shell structured η-Fe2O3 nanoparticles with versatile configurations via the Ostwald ripening process. By simply controlling the amount of PVP and reaction time in solution, hollow or yolk–shell structured η-Fe2O3 nanoparticles with spherical, egg-like, olivary, elliptical, and shuttle-like configurations can be easily fabricated. The interior structures and morphologies of the particles are found to be effective ways to affect both the specific saturation magnetization and coercivity of the η-Fe2O3 nanoparticles.

In this paper, a simple way is developed for the synthesis of the ZnO micro-windbreak film (ZMW) based on layered basic zinc salt precursor. The ZnO products maintain the original morphologies of precursors without deformation. Scanning electron microscopy, transmission electron microscopy, infrared spectrum and X-ray diffraction are used to characterize the detailed structures of the as-prepared products. Because of better gas diffusion in single layer ordered flower arrays (highly exposed surfaces) and thin belt-like branches (high diffusion coefficient) than other hierarchical structures, ZMW exhibits the highest responses to benzene gas. High responses allow ZMW to be used for the detection of benzene at ppb-level. By simply sputtering the platinum on both faces of ZMW to enhance the surface reaction, the optimal operating temperature for benzene detection could be reduced to 350 °C and the responses are significantly improved.

Heterogeneous Au–Pt nanostructures have been synthesized using a sacrificial template-based approach. Typically, monodispersed Au nanoparticles are prepared first, followed by Ag coating to form core–shell Au–Ag nanoparticles. Next, the galvanic replacement reaction between Ag shells and an aqueous H2PtCl6 solution, whose chemical reaction can be described as 4Ag + PtCl62− → Pt + 4AgCl + 2Cl−, is carried out at room temperature. Pure Ag shell is transformed into a shell made of Ag/Pt alloy by galvanic replacement. The AgCl formed simultaneously roughens the surface of alloy Ag–Pt shells, which can be manipulated to create a porous Pt surface for oxygen reduction reaction. Finally, Ag and AgCl are removed from core–shell Au–Ag/Pt nanoparticles using bis(p-sulfonatophenyl)phenylphosphane dihydrate dipotassium salt to produce heterogeneous Au–Pt nanostructures. The heterogeneous Au–Pt nanostructures have displayed superior catalytic activity towards oxygen reduction in direct methanol fuel cells because of the electronic coupling effect between the inner-placed Au core and the Pt shell.

Engineering the structure and/or composition of Pt nanoparticles has been an effective approach to improve the catalytic activity on a mass basis. Herein we demonstrate for the first time the synthesis of core-shell CdSe@Pt nanocomposites at different CdSe/Pt molar ratios. By reducing platinum precursors with sodium citrate in the presence of previously formed CdSe nanocrystals in aqueous phase, uniform core-shell CdSe@Pt nanocomposites are obtained as the dominant product. These core-shell CdSe@Pt nanocomposites exhibit superior catalytic activity toward reactions in direct methanol fuel cells (DMFCs). The inner-placed CdSe core is helpful for saving a substantial amount of valuable platinum metal. In addition, this core-shell structure also offers a vivid example for investigation of the lateral strain effect of the substrate on the deposited layers, and its influence on the catalytic activity of metal catalysts.

Controlling the morphology of transition-metal nanoparticles (TMNPs) can be an effective way to produce nanomaterials with favourable properties (activity and selectivity, etc.). Here we reported the shape control syntheses of TMNPs including Ru, Rh, Pd, Os, Ir, Pt, alloy PtRu, PtOs, and PtRuOs by co-reducing their metal precursors and Ag(I) ions in an organic medium. In this approach, Ag(I) ions were reduced first for their higher reduction potential, leading to the formation of spherical Ag nanoparticles. Then the subsequently reduced atoms of other transition-metals grew on the pre-existing Ag nanoparticles, resulting in the TMNPs with spherical or quasi-spherical shapes. In the absence of Ag precursors, the TMNPs obtained under same experimental conditions were dominated by irregular shapes, for example, rods, multi-pods, worm-like, or star-like, etc. The dependence of the property on the shape of the particles was also demonstrated using the catalytic oxidation of methanol as an example.Graphical abstractAn Ag facilitated approach for the shape control of transition-metal nanoparticles was developed, which is actually built on the formation of core–shell Ag-metal structures although the syntheses were carried out in a one-pot way.Highlights► We developed a Ag-facilitated approach to control the shape of transition-metal nanoparticles (TMNPs). ► Quasi-spherically shaped TMNPs were prepared by co-reducing the metal precursors and Ag(I) ions in an organic medium. ► The shape control of TMNPs was actually based on the formation of core-shell Ag-metal structures. ► The Ag facilitated alloy TMNPs showed superior catalytic activities towards methanol oxidation.

Heterogeneous Au–Pt nanostructures have been synthesized using a sacrificial template-based approach. Typically, monodispersed Au nanoparticles are prepared first, followed by Ag coating to form core–shell Au–Ag nanoparticles. Next, the galvanic replacement reaction between Ag shells and an aqueous H2PtCl6 solution, whose chemical reaction can be described as 4Ag + PtCl62− → Pt + 4AgCl + 2Cl−, is carried out at room temperature. Pure Ag shell is transformed into a shell made of Ag/Pt alloy by galvanic replacement. The AgCl formed simultaneously roughens the surface of alloy Ag–Pt shells, which can be manipulated to create a porous Pt surface for oxygen reduction reaction. Finally, Ag and AgCl are removed from core–shell Au–Ag/Pt nanoparticles using bis(p-sulfonatophenyl)phenylphosphane dihydrate dipotassium salt to produce heterogeneous Au–Pt nanostructures. The heterogeneous Au–Pt nanostructures have displayed superior catalytic activity towards oxygen reduction in direct methanol fuel cells because of the electronic coupling effect between the inner-placed Au core and the Pt shell.

Engineering the structure and/or composition of Pt nanoparticles has been an effective approach to improve the catalytic activity on a mass basis. Herein we demonstrate for the first time the synthesis of core-shell CdSe@Pt nanocomposites at different CdSe/Pt molar ratios. By reducing platinum precursors with sodium citrate in the presence of previously formed CdSe nanocrystals in aqueous phase, uniform core-shell CdSe@Pt nanocomposites are obtained as the dominant product. These core-shell CdSe@Pt nanocomposites exhibit superior catalytic activity toward reactions in direct methanol fuel cells (DMFCs). The inner-placed CdSe core is helpful for saving a substantial amount of valuable platinum metal. In addition, this core-shell structure also offers a vivid example for investigation of the lateral strain effect of the substrate on the deposited layers, and its influence on the catalytic activity of metal catalysts.