A Cu-Pd single-atom alloy catalyst for highly efficient NO reduction.

Area of Science:

• Catalysis
• Materials Science
• Environmental Chemistry

Background:

• Nitrogen oxides (NOx) are major air pollutants contributing to smog and acid rain.
• Efficient catalytic converters are crucial for reducing NOx emissions from industrial processes and vehicles.
• Developing cost-effective and highly selective catalysts for NOx reduction remains a significant challenge.

Purpose of the Study:

• To synthesize and characterize novel Copper-Palladium (Cu-Pd) alloy nanoparticles supported on alumina (Al2O3) for deNOx applications.
• To investigate the catalytic performance of these Cu-Pd catalysts in the reduction of nitrogen monoxide (NO) by carbon monoxide (CO).
• To elucidate the structure-activity relationship and the mechanism underlying the enhanced catalytic performance.

Main Methods:

• Synthesis of Cu-Pd alloy nanoparticles supported on Al2O3 with varying Cu/Pd ratios.
• Characterization using X-ray Diffraction (XRD), High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy (HAADF-STEM), X-ray Absorption Fine Structure (XAFS), and Fourier-Transform Infrared Spectroscopy (FT-IR).
• Catalytic activity testing for deNOx reactions under various conditions, including kinetic and Density Functional Theory (DFT) studies.

Main Results:

• A single-atom alloy structure was successfully formed at a Cu/Pd ratio of 5, with isolated Pd atoms dispersed on the Cu matrix.
• The Cu5Pd/Al2O3 catalyst demonstrated superior catalytic activity and nitrogen (N2) selectivity in NO reduction by CO compared to Pd/Al2O3.
• Complete conversion of NO to N2 was achieved at 175°C with remarkable long-term stability (≥30 h).
• High performance was maintained in the presence of oxygen (O2) and propene (C3H6), achieving a 90% reduction in Pd usage with minimal nitrous oxide (N2O) formation.
• Kinetic and DFT studies identified N-O bond breaking of the (NO)2 dimer as the rate-determining step, kinetically facilitated by isolated Pd atoms.

Conclusions:

• The single-atom alloy structure of Cu-Pd nanoparticles is key to achieving high deNOx catalytic performance.
• This catalyst offers an efficient and stable solution for NOx reduction, significantly reducing precious metal loading.
• The findings provide valuable insights into the design of advanced catalysts for environmental remediation.