Given tunable hybridization structures in solid solutions, fascinating electromagnetic (EM) properties can be achieved for regulating EM wave (EMW) absorption. Herein, a novel metal–organic cooperative interactions method is proposed to manipulate the vacancy, interstitial, substitutional, and heterointerface structures in molybdenum disulfide (MoS2) solid solution simultaneously, thence meeting the synergistic polarization loss on various point and face sites. Assisted by the coordination between Cu2+ and polydopamine (PDA), the effect of Cu modification on MoS2 is highly improved, which further lead to polarization loss on S vacancy, interstitial Cu, substitutional N, and heterointerface between carbon and MoS2. Contributing to the synergetic effect among multiple polarizations, the Cu/C@MoS2 solid solution exhibit ultrahigh EMW absorption performance, of which EMA with twice PDA delivers the effective absorption bandwidth of 7.12 GHz and minimum reflection loss of −48.22 dB (2.5 mm). The energy attenuation of Cu/C@MoS2 improved almost 266.7% and 222.2% than C@MoS2 and Cu@MoS2, respectively. Finally, this work reveals the structural dependency of solid solution materials of EMW absorption and establishes an entirely new polarization loss model.
The Cu-based nanocatalysts have shown a high selectivity toward selective hydrogenation reaction, but the underlying catalytic mechanism is still murky. Herein, we report a new gram-scale strategy for realizing the single atom Cu site incorporated into the melem ring of graphitic carbon nitride (Cu 1 /CN) for understanding the catalytic mechanism of a hydrogenation reaction. The as-synthesized Cu 1 /CN exhibits unprecedented selectivity (100%), high activity (TOF = 2.9 × 10 3 h −1 ), and outstanding stability for selective hydrogenation of 4-nitrostyrene. We reveal that the presence of hydroxymethyl from trimethylolmelamine is beneficial to atomically disperse Cu atoms in the CN. X-ray absorption fine structure tests reveal that the Cu atom of Cu 1 /CN is dominated by the quaternary coordination way (Cu−N 4 ) in the melem ring of CN. Density functional theory calculations confirm that the high reactivity and selectivity originate from the anchored Cu sites creating the optimal chemical environment for the highly efficient hydrogenation reaction.
Introducing oxophilic metals into Pt‐based alloy catalysts can effectively alleviate the poisoning by CO intermediates (CO*) during methanol oxidation reactions (MOR). However, excessive oxophilic metals on the surface of catalysts tend to form thermodynamically stable carbonyl compound‐like structures, occupying electrocatalytically active sites, which is not conducive to the enhancement of catalytic activity. Herein, a kind of surface segregated FePtRh nanoflowers for effectively eliminating the CO* poisoning during MOR electrocatalysis is presented. The FePtRh nanoflowers are constituted by the Rh‐rich core and Fe‐rich shell. The optimized Fe21Pt66Rh13/C shows a high mass activity of 3.90 A mgPt−1 and a specific activity of 4.85 mA cm−2. It is confirmed that the electron transfer from Pt to Rh or Fe atoms is beneficial for the higher anti‐CO poisoning ability, which mainly originate from the alloying of Rh atoms and surface‐segregated structures. Density functional theory calculations reveal the decreased electrons adsorbed by CO* on both Pt–Pt bridge sites and top sites weakens the strong adsorption energy between Pt atoms and CO* intermediates. The optimal nanoflowers also show excellent performance toward ethanol oxidation reaction (EOR) with a high mass activity of 2.76 A mgPt−1 and the enhanced anti‐CO poisoning ability, as well as the improved stability.
Tuning asymmetric coordination of metal single-atom (SA) sites can provide a new opportunity for optimizing the electronic structure of catalysts to achieve efficient catalysis, however, achieving such controllable design remains a grand challenge. Herein, an asymmetrically coordinated Co-N 4 P SA site as a new catalyst system for achieving superior dehydrogenation catalysis of formic acid (HCOOH) is reported. The experimental results show that the Co atom is coordinated by four N atoms and one asymmetric P atom, forming the unique Co-N 4 P SA sites. The Co-N 4 P SA sites exhibit an impressive mass activity of 4285.6 mmol g -1 h -1 with 100% selectivity and outstanding stability for HCOOH dehydrogenation catalysis at 80 °C, which is 5.0, 25.5, and 23.1 times that of symmetrically coordinated Co-N 4 SA sites, commercial Pd/C and Pt/C, respectively. The in situ ATR-IR analysis demonstrates the mono-molecular H 2 produced mechanism over Co-N 4 P SA sites, and theoretical calculations further reveal that the asymmetric P sites not only can boost the CH bond cleavage of HCOO* by largely reducing the energy barrier but also facilitate the proton adsorption to achieve the fast generation of H 2 in Co-N 4 P SA sites. This study opens a new way for rationally designing novel SA sites to achieve efficient catalysis.
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