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. 2019 Aug 5;10(36):8292-8298.
doi: 10.1039/c9sc03172c. eCollection 2019 Sep 28.

A Cu-Pd Single-Atom Alloy Catalyst for Highly Efficient NO Reduction

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Free PMC article

A Cu-Pd Single-Atom Alloy Catalyst for Highly Efficient NO Reduction

Feilong Xing et al. Chem Sci. .
Free PMC article

Abstract

A series of Cu-Pd alloy nanoparticles supported on Al2O3 were prepared and tested as catalysts for deNO x reactions. XRD, HAADF-STEM, XAFS, and FT-IR analyses revealed that a single-atom alloy structure was formed when the Cu/Pd ratio was 5, where Pd atoms were well isolated by Cu atoms. Compared with Pd/Al2O3, Cu5Pd/Al2O3 exhibited outstanding catalytic activity and N2 selectivity in the reduction of NO by CO: for the first time, the complete conversion of NO to N2 was achieved even at 175 °C, with long-term stability for at least 30 h. High catalytic performance was also obtained in the presence of O2 and C3H6 (model exhaust gas), where a 90% decrease in Pd use was achieved with minimum evolution of N2O. Kinetic and DFT studies demonstrated that N-O bond breaking of the (NO)2 dimer was the rate-determining step and was kinetically promoted by the isolated Pd.

Figures

Fig. 1
Fig. 1. (a) HAADF-STEM image of Cu5Pd/Al2O3 and (b) size distribution of the nanoparticles. (c) Elemental map of the Pd + Cu overlayer, as acquired by EDS. (d) High-resolution image of a single nanoparticle.
Fig. 2
Fig. 2. (a) FT-IR spectra of CO adsorbed on the prepared catalysts. (b) Fourier transforms of the Pd K-edge EXAFS spectra of the Pd-based catalysts.
Fig. 3
Fig. 3. (a) NO conversion to N2 during the NO reduction by CO over Pd, Cu, and Cu–Pd catalysts as a function of reaction temperature (NO, CO: 0.5%, GHSV = 80 000 h–1). (b) Comparison between CN2 and CN2O in NO reduction in the presence of O2 and C3H6. (c) Stability test for Cu5Pd/Al2O3 in the NO + CO reaction at low temperatures (NO, CO: 0.5%, GHSV = 40 000 h–1).
Fig. 4
Fig. 4. Arrhenius-type plots obtained in the NO + CO reaction over Cu5Pd/Al2O3, Cu/Al2O3, and Pd/Al2O3 catalysts.
Fig. 5
Fig. 5. Energy diagrams of NO adsorption, dimerization, and the dimer's decomposition over pure and Pd-doped Cu(211) surfaces. The total energy of the slab and free NO was set to zero.
Fig. 6
Fig. 6. Energy diagrams of N2O bending (initial (IS) to intermediate (MS) states) and its subsequent decomposition to N2 and O (MS to final state (FS)) over the Cu(211) surface. The total energy of slab and free N2O was set to zero.

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