Insights into N-Coordinated Bimetallic Site Synergy during NO Selective Catalytic Reduction by CO
Yue Ding, Yong Shi, Wei Xiong, Jian Heng Sun, Cheng Li, Ya Qi Zhang, Jing Guo
Abstract
The nature of the synergistic effect in bimetallic catalysts remains a challenging issue, due to the difficulty in understanding the adjacent interaction between dual metals at the atomic level. Herein, a CuFe–N/C catalyst featuring diatomic metal–nitrogen sites was prepared through a sequential ion exchange strategy and applied for NO selective catalytic reduction by CO (CO-SCR). The bimetallic CuFe–N/C catalyst exhibits high N2 selectivity with a NO conversion efficiency of nearly 100% over a wide temperature range from 225 to 400 °C, significantly higher than that of its single-component counterparts. The synergistic effect of bimetallic Cu–Fe sites is well revealed using the combined in situ FTIR technique and DFT calculations. Bifunctional Cu–Fe sites are demonstrated not only to provide two different preferential adsorption centers for the CO molecule and ONNO intermediate but also to achieve a complete electron cycle for efficient interfacial electron transfer upon ONNO uptake. The unique electron transfer mechanism stemmed from 4s-3d-type electron coupling, and different 3d shell fillings of Cu (3d10) and Fe (3d6) atoms are presented. These fundamental insights pave the way for the understanding of N-coordinated bimetallic site synergy and rational design of highly active atomic-scale metal catalysts for SCR applications.