Herein, we report a novel carbothermal welding strategy to prepare atomically dispersed Pd sites anchored on a three-dimensional (3D) ZrO2 nanonet (Pd1@ZrO2) via two-step pyrolysis, which were evolved from isolated Pd sites anchored on linker-derived nitrogen-doped carbon (Pd1@NC/ZrO2). First, the NH2–H2BDC linkers and Zr6-based [Zr6(μ3-O)4(μ3-OH)4]12+ nodes of UiO-66-NH2 were transformed into amorphous N-doped carbon skeletons (NC) and ZrO2 nanoclusters under an argon atmosphere, respectively. The NC supports can simultaneously reduce and anchor the Pd sites, forming isolated Pd1–N/C sites. Then, switching the argon to air, the carbonaceous skeletons are gasified and the ZrO2 nanoclusters are welded into a rigid and porous nanonet. Moreover, the reductive carbon will result in abundant oxygen (O*) defects, which could help to capture the migratory Pd1 species, leaving a sintering-resistant Pd1@ZrO2 catalyst via atom trapping. This Pd1@ZrO2 nanonet can act as a semi-homogeneous catalyst to boost the direct synthesis of indole through hydrogenation and intramolecular condensation processes, with an excellent turnover frequency (1109.2 h–1) and 94% selectivity.

The sintering of supported metal nanoparticles is a major route to the deactivation of industrial heterogeneous catalysts, which largely increase the cost and decrease the productivity. Here, we discover that supported palladium/gold/platinum nanoparticles distributed at the interface of oxide supports and nitrogen-doped carbon shells would undergo an unexpected nitrogen-doped carbon atomization process against the sintering at high temperatures, during which the nanoparticles can be transformed into more active atomic species. The in situ transmission electron microscopy images reveal the abundant nitrogen defects in carbon shells provide atomic diffusion sites for the mobile atomistic palladium species detached from the palladium nanoparticles. More important, the catalytic activity of sintered and deactivated palladium catalyst can be recovered by this unique N-doped carbon atomization process. Our findings open up a window to preparation of sintering-resistant single atoms catalysts and regeneration of deactivated industrial catalysts.

Polynary single-atom structures can provide synergistic functions based on multiple active sites and reactants, which significantly improve their catalytic performance. However, the structure−activity relationships of these special structures remain elusive. Here, we report atomically dispersed Fe−Ni dual-metal catalysts anchored on N-doped graphene as an efficient catalyst for CO oxidation. The density functional theory (DFT) calculation results show that Ni serves as a catalytic nucleophilic center for CO adsorption, whereas Fe serves as an electrophilic center for O 2 adsorption, making full use of the dual-metal active sites. Thus, a heteronuclear Fe 1 Ni 1 @NGr catalyst with the synergistic effect of combining dissimilar metal atoms has better catalytic activity and lower propensity for CO poisoning than its homonuclear counterparts. Comparing the Langmuir−Hinshelwood (LH) and Eley− Rideal (ER) mechanisms for CO oxidation on Fe 1 Ni 1 @NGr, Ni 2 @NGr, and Fe 2 @NGr, we find that the LH mechanism with coadsorbed CO and O 2 is dynamically more favorable. In addition, residual oxygen atoms attached to the Fe−Ni active sites can easily react with additional CO molecules, indicating the achievement of a high recycling rate. These findings reveal a synergistic catalytic mechanism of graphene-supported atomically dispersed transition dual-metal catalysts, providing important guidance for the rational design of atomically dispersed catalysts.

Platinum (Pt)-based nanostructures are the most efficient catalysts for the oxygen reduction reaction (ORR) in acid media. Here, Pt Ni wavelike nanowires (W-NWs) have been synthesized by etching Pt Ni@PtNi core-shell nanowires with 2,5-dihydroxyterephthalic acid for 24 hours. Compared to the commercial Pt/C catalyst, the free-standing Pt Ni W-NWs show improvements of up to 9.3 times for mass activity and 12.6 times for specific activity, respectively.