RESUMEN
Pd/C catalysts have been widely applied in the debenzylation process due to their excellent ability of hydrogenolysis. However, they have been suffering from the problems of agglomeration and loss of active components, which lead to decreased and unstable activity. Thus, it is still a challenge to achieve Pd/C catalysts with high activity and stability. Herein, we propose a strategy for preparing Pd/C catalysts on porous carbon hollow spheres by a microwave discharge method. Due to the high-temperature property and reducibility of microwave discharge, Pd precursors can be rapidly reduced, resulting in well-dispersed Pd nanoparticles with a small size on the carbon carrier. Besides, the matched mesopores in the carbon hollow spheres can anchor Pd nanoparticles and effectively reduce the agglomeration and loss of Pd nanoparticles during the catalytic reaction. As a result, the as-prepared Pd/mesoporous carbon hollow spheres exhibit high and stable activity in the debenzylation reaction.
RESUMEN
Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal-organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials.
RESUMEN
High-loading Pt/C catalysts play an important role in the practical application of metal-air batteries and fuel cells because of their superior activity, high conductivity, and commercial availability. It is well known that high loadings always lead to the agglomeration of Pt nanoparticles, resulting in a loss of catalytic activity and stability; thus, it still remains a challenge to prepare high-loading Pt/C catalysts with high dispersion and small particle sizes. Here, we introduce a surfactant-assisted microwave discharge method to prepare high-loading (>40 wt %) Pt/C electrocatalysts with ultrafine particle sizes (â¼3.19 nm) and good dispersion. Benefitting from the high-temperature property and reducibility of carbon-induced-arc, the surfactant and Pt precursors undergo rapid decomposition, reduction, and carbonization, generating the structure of Pt@C on carbon black. The carbon derived from the surfactant can not only inhibit the agglomeration of Pt nanoparticles but also prevent the Pt core from toxication, ensuring high activity and stability of the high-loading Pt/C catalyst. When evaluated in the oxygen reduction reaction, the as-prepared Pt/C catalyst demonstrates a comparable activity and better methanol resistance to commercial Pt/C.