Carbon Defects on\nN‑Doped Carbon Promote Catalytic\nActivity of Pd Nanoparticles for the Selective Hydrogenation of Quinoline

The activation process is a key step\nin preparing porous carbon.\nHerein, three kinds of green activators were separately used to successfully\nprepare N-doped porous carbons through a two-step strategy: hydrothermal\ncarbonization and chemical activation using microcrystalline cellulose\nas the carbon source and urea as the nitrogen source. Palladium was\ndeposited on these N-doped microcrystalline cellulose-based carbons\n(NMC-X, where X represents the activator) via a traditional deposition–precipitation\nmethod, and the resulting Pd nanoparticle catalysts (Pd/NMC-X) showed\nhigh activity in the selective hydrogenation of quinoline under mild\nconditions, particularly Pd/NMC-ZC (ZC, zinc carbonate), which achieved\ncomplete conversion of quinoline within 100 min at 40 °C and\n4 atm H<sub>2</sub>. Characterization results suggest that the high\nactivity of Pd/NMC-ZC is mainly attributed to the special electronic\nstructure of its Pd species, particularly the distribution of valence\nstates and reducibility of Pd and the high hydrogen spillover capacity\nbetween Pd and NMC-ZC. The chemical activation by ZC leads to the\nformation of multiple defect sites on the carbon skeleton, modifying\nthe carbon surface properties to enhance hydrogen spillover. This\nalso provides an excellent environment for Pd nanoparticle anchoring,\nthus increasing the Pd-support interactions and regulating the electronic\nstructure of Pd.