Hybrid multi-metallic nanocatalysts have attracted increasing attention because of the synergistic effect of metal species and considerably improved catalytic performance, but they often suffer from severe sintering and poor stability. Here, we show a facile strategy for preparing subnanometric hybrid bimetallic clusters Pd-M(OH) 2 (M = Ni, Co) within silicalite-1 (S-1) zeolite via a hydrothermal synthesis method. The hybrid bimetallic nanocatalysts exhibit excellent shape-selective catalytic performance and superior thermal stability. The incorporation of secondary Ni(OH) 2 species in S-1 can considerably increase the catalytic activity of the Pd nanoclusters for the dehydrogenation of formic acid (FA) as a result of the electron-enriched Pd surface and bimetallic interfacial effect. Notably, the 0.8Pd0.2Ni(OH) 2 @S-1 catalyst affords the highest initial turnover frequency value, up to 5,803 hr À1 toward complete FA decomposition without any additives at 60 C. The superior catalytic properties and excellent stability of the subnanometric hybrid bimetallic clusters confined in zeolites create new prospects for their practical high-performance catalytic application.

Mesoporous spinel nickel cobaltite (NiCo2O4) nanostructures were synthesized via a facile chemical deposition method coupled with a simple post-annealing process. The physicochemical properties were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and nitrogen sorption measurements. The electrocatalytic performances were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) tests. The obtained NiCo₂O₄ materials exhibit typical agglomerate mesoporous nanostructures with a large surface area (190.1 m(2) g(-1)) and high mesopore volume (0.943 cm(3) g(-1)). Remarkably, the NiCo₂O₄ shows much higher catalytic activity, lower overpotential, better stability and greater tolerance towards urea electro-oxidation compared to those of cobalt oxide (Co₃O₄) synthesized by the same procedure. The NiCo₂O₄ electrode delivers a current density of 136 mA cm(-2) mg(-1) at 0.7 V (vs. Hg/HgO) in 1 M KOH and 0.33 M urea electrolytes accompanied with a desirable stability. The impressive electrocatalytic activity is largely ascribed to the high intrinsic electronic conductivity, superior mesoporous nanostructures and rich surface Ni active species of the NiCo₂O₄ materials, which can largely boost the interfacial electroactive sites and charge transfer rates for urea electro-oxidation, indicating promising applications in future wastewater remediation, hydrogen production and fuel cells.

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An organic−inorganic hybrid heterogeneous catalyst system was synthesized by covalently anchoring oxodiperoxo molybdenum complexes [(L−L)MoO(O2)2] (L−L = (3-triethoxysilylpropyl)[3-(2-pyridyl)-1-pyrazolyl]acetamide) onto the mesoporous silica MCM-41 (Si−MCM-41) and aluminosilicate MCM-41 (Al−MCM-41) materials. Characterization of the functionalized materials by powder X-ray diffraction (XRD), N2 adsorption, and solid-state CP-MAS NMR spectroscopy (13C and 29Si) demonstrates that the oxodiperoxo molybdenum complexes are grafted successfully into the mesoporous MCM-41 materials. The structures of both the mesoporous materials and the molybdenum complex are preserved during the grafting process. All the hybrid materials are active and truly heterogeneous catalysts for the liquid-phase epoxidation of cyclooctene with tBuOOH as the oxygen source. The catalytic properties (activity and recyclability) of the supported materials can be improved by their further silylation using Me3SiCl, which can be explained by the increase of hydrophobicity of the mesoporous surface due to removal of residual Si−OH groups. The modified aluminosilicate MCM-41 materials show higher activities than the corresponding siliceous materials, which might be due to the incorporation of Lewis acidic centers.

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