Bing H. Chen

Decoration of Co/Co3O4 nanoparticles with Ru nanoclusters: a new strategy for design of highly active hydrogenation

Ru/Co/Co3O4/C (Ru nanoclusters-on-Co/Co3O4 nanoparticles) has an unexpected enhancement of activity for benzene hydrogenation which is about 2500 times higher than Ru–Co nanoalloy/C. Detailed nanostructure characterization of Ru/Co/Co3O4/C has revealed that the high activity originates from a synergetic multifunction of the catalytic Ru, Co and Co3O4 sites on the nanocluster/nanoparticle surfaces.

Ruthenium–nickel–nickel hydroxide nanoparticles for room temperature catalytic hydrogenation

Improving the utilization of metals in heterogeneous catalysts with excellent catalytic performance, high selectivity and good stability represents a major challenge. Herein a new strategy is disclosed by enabling a nanoscale synergy between a transition metal and a noble metal. A novel Ru/Ni/Ni(OH)2/C catalyst, which is a hybrid of Ru nanoclusters anchored on Ni/Ni(OH)2 nanoparticles (NPs), was designed, prepared and characterized. The Ru/Ni/Ni(OH)2/C catalyst exhibited a remarkable catalytic activity for naphthalene hydrogenation in comparison with existing Ru/C, Ni/Ni(OH)2/C and Ru–Ni alloy/C catalysts. This is mainly attributed to the interfacial Ru, Ni and Ni(OH)2 sites of Ru/Ni/Ni(OH)2/C, where hydrogen is adsorbed and activated on Ru while Ni transfers the activated hydrogen species (as a “bridge”) to the activated naphthalene on Ni(OH)2 sites, producing decalin through a highly effective pathway.

Synthesis of Different Ruthenium Nickel Bimetallic Nanostructures and an Investigation of the Structure–Activity Relationship for Benzene Hydrogenation to Cyclohexane

The catalytic properties of catalysts are generally highly dependent on their nanostructures in most heterogeneous catalytic reactions. Therefore, to acquire targeted catalytic activity, selectivity, and stability, catalysts with a specific nanostructure should be designed and synthesized. Herein, Ru‐Ni bimetallic nanoparticles with different nanostructures, Ru‐Ni alloy, Ru@Ni, and Ru clusters‐on‐Ni on carbon, have been synthesized by annealing Ru‐Ni/C in flowing N2+10 % H2 at different temperatures. The various nanostructures of the Ru‐Ni bimetallic nanoparticles have been characterized and their catalytic behaviors were evaluated using benzene hydrogenation to cyclohexane. The relationship between the Ru‐Ni bimetallic nanostructures and their catalytic performance is presented. It was found that Ru‐Ni alloy/C and Ru clusters‐on‐Ni/C are much more active than Ru@Ni/C. This study also provides a simple method to design and control the nanostructures of the Ru‐Ni bimetallic nanoparticles.

Activity and kinetics of ruthenium supported catalysts for sodium borohydride hydrolysis to hydrogen

Ru–RuO2/C prepared by galvanic replacement has high catalytic activity for sodium borohydride hydrolysis. In the present study, a series of Ru–RuO2/C catalysts, Ru–RuO2/C reduced, RuO2/C and Ru supported on Ni foam (Ru/Ni foam) are prepared and characterized. Results show that RuO2 on Ru–RuO2/C is formed from both the consumption of the parent Ni and NiO nanoparticles and the disproportionation of RuCl3 with epitaxial growth of Ru species. The quantity of RuO2 with oxygen vacancies in Ru–RuO2/C determines the hydrolysis activity for sodium borohydride. In contrast to Ru–RuO2/C, Ru/Ni foam without oxygen vacancies has the lower hydrolysis activity. Results of kinetics calculation further confirm that without mass transfer limitation, Ru–RuO2/C has lower intrinsic activation energy and correspondingly higher catalytic activity due to existence of oxygen vacancies than those from Ru–RuO2/C reduced, RuO2/C, Ru/Ni foam and catalysts from the literature.

Effect of the thermal treatment temperature of RuNi bimetallic nanocatalysts on their catalytic performance for benzene hydrogenation

The thermal treatment temperature of bimetallic nanocatalysts plays an important role in determining their catalytic performance. In this study, the synthesis of RuNi bimetallic nanoparticles (BNPs) supported on carbon black catalysts (denoted as RuNi BNSC) via hydrazine hydrate reduction and galvanic replacement reaction methods was reported. Then the effect of the annealing temperature in N2 (uncalcined, 160, 230, 280, 380, 480, 580 and 680 °C) of RuNi BNSC on its catalytic activity for the benzene hydrogenation reaction was investigated. It was found that RuNi BNSC calcined at 380 °C exhibited outstanding catalytic activity in the liquid phase hydrogenation of benzene to cyclohexane, which was about 3–4 times higher than that of RuNi BNSC calcined at 680 °C, while RuNi BNSC annealed at 480 °C had no activity for this reaction. The characterization results of the catalysts indicated that various thermal treatment temperatures in N2 affected the RuNi BNP size, chemical states of Ru and Ni, and RuNi bimetallic nanostructures and thus the catalytic properties.

Oxygen-vacancy-promoted catalytic wet air oxidation of phenol from MnOx–CeO2

Catalytic oxidation can be effectively promoted by the presence of oxygen vacancies on the catalyst surface. In this study, the effect of oxygen vacancies on the catalytic wet air oxidation (CWAO) of phenol was investigated with CeO2 and MnOx–CeO2 as catalysts. CeO2 and MnOx–CeO2 catalysts with different amounts of oxygen vacancies were obtained via hydrothermal methods and applied for the CWAO of phenol. It was found that CeO2 and MnOx–CeO2 nanorods were much more active than the cubic nanorods. The physicochemical properties of the samples were characterized by TEM, XRD, BET, XPS, and H2-TPR techniques. The results revealed that the presence of oxygen vacancies in CeO2 and MnOx–CeO2 catalysts could increase the oxidizing ability of the catalysts surface. The addition of Mn could greatly improve the adsorption ability of CeO2 and more efficiently oxidize phenol and its intermediates. The synergy between Mn and Ce could further improve the catalyst redox properties and produce a larger amount of active oxygen species, which is the reason why MnOx–CeO2 nanorods are the most active catalysts among the catalysts investigated in this study.

Tuning Surface Properties and Catalytic Performances of Pt–Ru Bimetallic Nanoparticles by Thermal Treatment

The surface structure and catalytic properties of Pt–Ru bimetallic catalysts with identical bulk composition can be continuously tuned by treatment at different temperatures. The activity of these catalysts in CO oxidation was positively related to the treatment temperature, but the opposite trend was observed for the solvent‐free oxidation of benzyl alcohol. It was found that migration of Pt to the surface occurred when the treatment temperature was increased. During this process, the surface of the Pt–Ru nanoparticles changed from a Ru‐rich surface to a Pt‐rich surface. The electronic interactions between Pt and Ru became stronger with increased treatment temperature, and the amount of oxidized Pt species on the surface was higher for the samples treated at higher temperatures. Therefore, oxidized Pt species are more active in CO oxidation than other metallic species, but are less active in the selective oxidation of benzyl alcohol.

Synthesis of Ru/CoNi crystals with different morphologies for catalytic hydrogenation

Cobalt–nickel alloy crystals with different morphologies, such as flower-like, column-like, mushroom-like and dendrite-like, were prepared by a facile hydrothermal or solvothermal reduction approach without the addition of any surfactant, using hydrazine hydrate as a reducing agent, ethanediamine as a capping agent and a mixture of nickel(II) chloride hexahydrate (NiCl2·6H2O) and cobalt(II) chloride hexahydrate (CoCl2·6H2O) as a precursor. The effect of hydrothermal temperature (120, 150 or 180 °C) and solvent (water or ethanol) on the shape of the CoNi crystals was investigated in this work. The corresponding Ru/CoNi catalysts (Ru-on-CoNi nanocrystals) were obtained via a galvanic replacement reaction. The sizes, element chemical states, morphologies and structures of the CoNi and Ru/CoNi samples were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and high-sensitivity low-energy ion scattering (HS-LEIS) techniques. The catalytic performance of the as-synthesized catalysts was evaluated by using the benzene hydrogenation reaction. The Ru/CoNi catalyst with a dendrite-like morphology exhibited the highest catalytic hydrogenation activity among the Ru/CoNi catalysts with different shapes. This was mainly due to its high Ru dispersion, many defect sites and positive synergistic effect compared with ruthenium, nickel and cobalt related species. Importantly, the cost of recycling the Ru/CoNi catalysts was relatively low because they could be recycled by magnetic separation.

δ-MnO2 with an ultrahigh Mn4+ fraction is highly active and stable for catalytic wet air oxidation of phenol under mild conditions

δ-MnO2 with a very high amount of Mn4+ showed high catalytic activity and stability for the catalytic wet air oxidation (CWAO) of phenol at a very low temperature of 70 °C. The abundance of Mn4+ and reactive surface oxygen species in this catalyst, its resistance to Mn leaching, and its repeatable Mn4+/Mn3+ (Mn4+/Mn2+) redox cycles contributed greatly to its remarkable catalytic performance.

The effect of weak acid anions on the selective catalytic wet air oxidation of aqueous ammonia to nitrogen

In this work, the effect of weak acid anions on the ammonia removal has been extensively studied for the process of selective catalytic wet air oxidation (CWAO) of ammonia to nitrogen. It is found that the presence of weak acid anions can effectively enhance the ammonia conversion and selectivity towards nitrogen. The combination between the weak acid anions and H+ to produce weak acid molecules is responsible for such enhancement. Firstly, the H+ consumption of weak acid anions can increase the NH3 concentration and thus the reactivity of ammonia oxidation, due to the shift to NH3 on the equilibrium of NH4+/NH3. Secondly, the competition combination with H+ between the weak acid anions and NO2− can increase the concentration of NO2− and thus boosts the disproportionation reaction between NH4+ and NO2− to produce nitrogen.