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. 2025 Jan 2;16(1):26.
doi: 10.1038/s41467-024-54820-y.

Tuning the selectivity of NH3 oxidation via cooperative electronic interactions between platinum and copper sites

Lu Chen #  1 , Xuze Guan #  2 , Zhaofu Fei  3 , Hiroyuki Asakura  4 , Lun Zhang  2 , Zhipeng Wang  2 , Xinlian Su  2 , Zhangyi Yao  2 , Luke L Keenan  5 , Shusaku Hayama  5 , Matthijs A van Spronsen  5 , Burcu Karagoz  5 , Georg Held  5 , Christopher S Allen  6   7 , David G Hopkinson  6 , Donato Decarolis  5   8 , June Callison  8 , Paul J Dyson  9 , Feng Ryan Wang  10
Affiliations

Tuning the selectivity of NH3 oxidation via cooperative electronic interactions between platinum and copper sites

Lu Chen et al. Nat Commun. .

Abstract

Selective catalytic oxidation (SCO) of NH3 to N2 is one of the most effective methods used to eliminate NH3 emissions. However, achieving high conversion over a wide operating temperature range while avoiding over-oxidation to NOx remains a significant challenge. Here, we report a bi-metallic surficial catalyst (PtSCuO/Al2O3) with improved Pt atom efficiency that overcomes the limitations of current catalysts. It achieves full NH3 conversion at 250 °C with a weight hourly space velocity of 600 ml NH3·h-1·g-1, which is 50 °C lower than commercial Pt/Al2O3, and maintains high N2 selectivity through a wide temperature window. Operando XAFS studies reveal that the surface Pt atoms in PtSCuO/Al2O3 enhance the redox properties of the Cu species, thus accelerating the Cu2+ reduction rate and improving the rate of the NH3-SCO reaction. Moreover, a synergistic effect between Pt and Cu sites in PtSCuO/Al2O3 contributes to the high selectivity by facilitating internal selective catalytic reduction.

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Conflict of interest statement

Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1. Characterisation of PtSCuO/Al2O3 and PtNCuO/Al2O3.
a, b TEM images of PtSCuO/Al2O3 (the inset in a shows the particle size distribution. The average particle size was calculated based on more than 100 particles.); Pt L3-edge and Cu K-edge EXAFS of PtSCuO/Al2O3 (c) and PtNCuO/Al2O3 (d).
Fig. 2
Fig. 2. Evaluation of PtSCuO/Al2O3 in comparison to other catalysts in the NH3-SCO reaction.
a, b NH3 conversion and N2 selectivity as a function of temperature; c activation energy of PtSCuO/Al2O3, CuO/Al2O3 Pt/Al2O3; d WSHV with refs (Table S2–); e stability test of PtSCuO/Al2O3 at 200 °C; f activity of MSCuO/Al2O3 catalysts (M = Pt, Ru, Rh, Ag, or Au); g, h NH3 conversion and N2 selectivity as a function of Pt loading and temperature; i NH3 conversion of PtSCuO/Al2O3 with different Pt loadings at 200 °C. Reaction conditions: 50 mg catalyst, 5000 ppm NH3, 5% O2 balanced in He, gas flow: 100 mL/min, WHSV = 600 mL NH3·h−1·g−1.
Fig. 3
Fig. 3. Operando studies on the redox behaviour of Cu and Pt in different catalysts.
a operando Cu K-edge XAFS, signal intensity of the Cu+ 1s-4p transition peak at 8982 eV in a NH3/O2 atmosphere at different temperatures; b operando Pt L3-edge, signal intensity of the white line of the Pt L3-edge at 11567 eV in a NH3/O2 atmosphere at different temperatures (reaction conditions: 5000 ppm NH3, 5% O2 balanced in He, gas flow: 100 mL/min); c H2-TPR of different catalysts; operando Cu K-edge XANES spectra of PtSCu/Al2O3 (d), PtNCu/Al2O3 (e) and CuO/Al2O3 (f) in different gases at 200 °C; in situ NAP-NEXAFS spectra, Cu L-edge (AEY mode) of different catalysts at 200 °C under NH3 (g) or NH3/O2 (h) atmospheres; i Cu L-edge (AEY mode) of PtSCu/Al2O3 under various gas atmospheres at 200 °C (gas pressure 1 mbar).
Fig. 4
Fig. 4. Kinetic studies and adsorption behaviours of the PtSCuO/Al2O3 and CuO/Al2O3 catalysts.
Change of CuO:Cu2O ratio in PtSCuO/Al2O3 (a) and CuO/Al2O3 (b) with time under NH3 or O2 environments at different temperatures (the catalysts are exposed to a flow of 5000 ppm NH3/He or 5% O2/He with flow rate 15 mL/min); change of CuO:Cu2O ratio in the PtSCuO/Al2O3 catalyst with time under NH3 (d) and O2 (e) environments at different gas concentrations; reaction order for NH3 (c) and O2 (f) in the whole apparent reaction or half reaction; g operando Cu K-edge XANES spectra of the PtSCu/Al2O3, PtNCu/Al2O3 and CuO/Al2O3 catalysts under NH3 + O2 at 200 °C (5000 ppm NH3, 5% O2 balanced in He, gas flow: 100 mL/min); Comparation between TOF of the full NH3-SCO reaction and Cu2+ reduction rate in Cu/Al2O3 (h) and PtSCu/Al2O3 (i).
Fig. 5
Fig. 5. Operando DRIFTS studies.
Operando DRIFTS spectra of PtSCu/Al2O3 (a) and Cu/Al2O3 (b) as a function of temperature (the catalysts were exposed to a flow of 5000 ppm NH3 and 5% O2 for 20 min at different temperatures).
See this image and copyright information in PMC

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