Dual Pd-Acid Sites Confined in a Hierarchical Core-Shell Structure for Hydrogenation of Nitrobenzene

A core-shell structured Pd@TS-1@meso-SiO2 catalyst with confined Pd nanometals has been fabricated by one-pot synthesis, impregnation method and sol-gel method. With the promotion of acid sites and protection of mesoporous silica shell, Pd@TS-1@meso-SiO2 shows higher activity than commercial comparison and higher stability than sample without mesoporous silica shell in the hydrogenation of nitrobenzene. The schematic illustration of the synergy effect is also proposed.

Solvent-Mediated Synthesis of Hierarchical MOFs and Derived Urchin-Like Pd@SC/HfO2 with High Catalytic Activity and Stability

Carbon materials with hierarchical morphologies, pores, and compositions have attracted extraordinary attention due to their unique structural advantages and widespread applications. However, their controllable synthesis remains a grand challenge. Herein, a solvent-mediated strategy was demonstrated for the preparation of an urchin-like superstructure via modulating the hydrothermal condition (acetic acid/water ratio) of metal-organic frameworks (MOFs). The direct pyrolysis of a hierarchical NUS-6 precursor produced a well-defined carbon-based composite consisting of sulfur-doped carbon (SC) and HfO₂ with an urchin-like morphology and micro-/mesoporosity, while the doped S sites and oxygen vacancies of HfO₂ can help to anchor and activate Pd nanoparticles (NPs) through the strong host-guest interaction, which was further confirmed by the calculated results of the binding energy and differential charge density through density functional theory (DFT). The synthesized Pd@SC/HfO₂ composite exhibited extremely high catalytic activity and stability toward the water-phase hydrodeoxygenation of vanillin (conversion >99%, selectivity >99%), as well as good universality for the hydrogenation of a series of unsaturated hydrocarbons in an aqueous system. Remarkably, the catalytic activity and structural stability of Pd@SC/HfO₂ were largely maintained even after successive 10 cycles.

A rational synthesis of ultrasmall palladium-based alloys with superhydrophilicity as biocompatible agents and recyclable catalysts

As essential controlling parameters, the local surface area (size distribution) and polarity property of the surface molecules can determine the catalytic activity and biocompatibility directly.

Multifunctional Pd/MOFs@MOFs Confined Core-Shell Catalysts with Wrinkled Surface for Selective Catalysis

Process intensification, targeting the maximization of spatial-temporal productivity utilizing minimum energy and resources has always been the constant trends especially in chemical industry. In this regard, tandem reactions that are able to perform a multi-step reaction in a single pot by eliminating costly separation steps have been viewed as a typical paradigm. However, a spatial isolation of varied active sites with a controlled manner in a single catalyst to avoid deactivation and work synergistically is a challenging problem yet sometimes being overlooked. In this work, a spatial base-metal core-shell structured catalyst with wrinkled surface was successfully fabricated by a direct homoepitaxial growth method in an acid/water system, which exhibited increased hydrophobicity, exposure of active sites and significantly improved product selectivity towards one-pot Knoevenagel condensation-hydrogenation tandem reaction compared with the uncoated catalyst. Meanwhile, the catalytic performance was largely retained and the structural stability was maintained even after successive 8 cycles, which shows great promise for industrial applications.

Ultimate Corrosion to Pt-Cu Electrocatalysts for Enhancing Methanol Oxidation Activity and Stability in Acidic Media

Alloying platinum (Pt) with transition metals (M), as an established class of electrocatalysts, reduces the use of Pt and improves the electrocatalytic performance. However, the stability of transition metals in nanostructured platinum alloys is a fundamental and practical problem in electrocatalysis, due to leaching of transition metals under acidic operating condition. Here, a corrosion method has been developed for a Pt-Cu electrocatalyst with high activity (6.6 times that of commercial Pt/C) and excellent stability for the methanol oxidation reaction (MOR) under acidic operating conditions. The mechanism of formation has been studied, and possible mesostructured re-formation and atomic re-organization have been proposed. This work offers an effective strategy for the facile synthesis of a highly acid-stable PtM alloying and opens a door to high-performance design for electrocatalysts.