Tunnel-confined and quenching-anchored atomic Cu in transition metal oxides for efficient catalytic oxidation

doi:10.1016/S1872-2067(26)65177-7

Abstract

Abstract:

Atomic-level dispersed metal catalysts have garnered considerable attention in heterogeneous catalysis due to their ultrahigh atomic efficiency, exceptional catalytic activity, and well-defined active site structures. However, achieving complete atomic-level dispersion of non-precious metals at high mass loadings on metal oxide supports remains a significant challenge. Here, we report the synthesis of a catalyst with highly dispersed 2.6 wt% Cu species on the tunnel-structured α-MnO₂ (MnO₂-QCu) via a quenching strategy. This approach synergistically leverages the rapid nucleation characteristic of quenching and the confinement effect of the α-MnO₂ tunnel structure. Beyond the conventional approach to catalyst loading, the activated tunnel structure of α-MnO₂ can provide additional Cu anchoring sites, effectively increasing the number of accessible catalytically active sites. The resulting MnO₂-QCu exhibits superior activity in CO oxidation, outperforming most reported Mn-based catalysts, and demonstrates excellent durability over 100 h under humid conditions. Mechanistic studies reveal that MnO₂-QCu facilitates the dual activation of lattice and molecular oxygen, while the resulting Cu-V_O-Mn interfaces promote charge transfer and enhance O₂ adsorption and activation, thereby enabling efficient and stable catalytic oxidation. This work offers a general and feasible route to design high-loading single-atom catalysts on oxide supports for energy and environmental applications.

Key words: Atomic-level dispersed catalysts, High mass loading, Quenching strategy, Tunnel-structured MnO₂, CO oxidation

Jin Yang, Jiajin Lin, Changchun Ye, Yifei Li, Shumin Liu, Gaige Zhang, Shengjie Liu, Guangxu Chen. Tunnel-confined and quenching-anchored atomic Cu in transition metal oxides for efficient catalytic oxidation[J]. Chinese Journal of Catalysis, 2026, 89: 477-490.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65177-7

https://www.cjcatal.com/EN/Y2026/V89/I10/477

Figures/Tables 5

Fig. 1. Schematic illustration depicting variations in the anchoring sites of guest metal atoms during quenching, associated with different atomic packing configurations.

Fig. 2. (a) Schematic illustration of the synthesis process of MnO2-QCu via the quenching process. (b,c) TEM images of MnO2-QCu. (d) XRD patterns of pristine MnO2, MnO2-Qwater, and MnO2-QCu. (e) HAADF-STEM image of MnO2-QCu, along with IFFT images corresponding to the (211) I and (202) II lattice planes. (f) Aberration-corrected HAADF-STEM image of MnO2-QCu. (g) Intensity profiles extracted from the green and yellow dashed regions in (f). (h) HAADF-STEM image and corresponding EDX elemental mapping of Mn, O, Cu, and K in MnO2-QCu.

Fig. 3. (a) Raman spectra of MnO2, MnO2-Qwater, and MnO2-QCu. (b) EPR spectra of the corresponding catalysts. (c) High-resolution XPS spectra of the O 1s region of various catalysts. (d) Cu 2p XPS spectra of the MnO2-QCu. (e) The infrared Fourier transform spectroscopy of CO adsorption on MnO2 and MnO2-QCu catalysts at 5000 Pa, respectively. XPS spectra of Mn 2p (f) and Mn 3s (g) for MnO2, MnO2-Qwater, and MnO2-QCu. (h) Normalized Mn K-edge XANES spectra, with reference fingerprints indicating different Mn oxidation states. (i) EXAFS spectra of Mn K-edge, highlighting local coordination environments around Mn. (j) Normalized Cu K-edge XANES spectra of MnO2-QCu compared with reference compounds (Cu foil, Cu2O, and CuO). (k) EXAFS spectra at the Cu K-edge, revealing the local structure of Cu species in MnO2-QCu.

Fig. 4. (a) Light-off curves for the CO oxidation reaction over MnO2, MnO2-Qwater, and MnO2-QCu. (Reaction condition: 1 vol% CO, 16 vol% O2 balanced with N2, total flow rate = 50 mL min-1, WHSV = 60000 mL gcat-1 h-1). (b) Apparent activation energies of various catalysts (WHSV = 300000 mL gcat-1 h-1). (c) Long-term stability test of CO oxidation at 120 °C for 70 h. (d) Light-off curves for the CO oxidation reaction under humid conditions (Reaction conditions: 5 vol% H2O, 1 vol% CO, 16 vol% O2 balanced with N2, total flow rate = 50 mL min-1, WHSV = 60000 mL gcat-1 h-1). (e) Comparison of T100 values across various catalysts under dry versus humid conditions. (f) Water tolerance assessment of MnO2-QCu during CO oxidation with periodic addition of 5 vol% H2O.

Fig. 5. (a) H2-TPR profiles of MnO2, MnO2-Qwater, and MnO2-QCu. (b) EPR spectra of superoxide O2-? species captured by DMPO as a spin-trapping agent. (c) CO-TPD profiles of MnO2, MnO2-Qwater and MnO2-QCu catalysts. (d) CO-TPSR curves showing CO2 formation over time. (e) CO-TPSR curves showing CO2 release and carbonate decomposition over temperature. In-situ time-resolved infrared spectra of CO adsorption on MnO2 (f) and MnO2-QCu (g) measured under 5 vol% CO at 5000 Pa. In-situ DRIFTS spectra collected during CO oxidation on MnO2 (h) and MnO2-QCu (i) under a flow of 1 vol% CO and 16 vol% O2 in N2 at different temperatures. (j) The proposed mechanisms for CO oxidation on the MnO2-QCu catalyst. (k) Schematic of CO oxidation over Cu-loaded MnO2 frameworks.

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