Basic understanding of Cu-SSZ-13 in catalyzing low-temperature selective catalytic reduction of NOx by ammonia

The development of Cu-SSZ-13 represents a significant breakthrough in the field of NO_x removal from mobile exhaust, demonstrating excellent selective catalytic reduction (SCR) activity across a broad temperature range (200–500°C). However, the limited reactivity of Cu-SSZ-13 at temperatures below 200°C poses a challenge for the removal of NO_x emitted during vehicle cold starts. To stimulate new efforts to enhance low-temperature SCR performance, this review provides a fundamental understanding of the nature of Cu-SSZ-13 in catalyzing the SCR reaction. The structures, coordination environments, and oxidation states of Cu²⁺ during the SCR reaction, as well as the redox cycle pathway of Cu²⁺ ions and the characteristics of the rate-determining step, were discussed. Based on these insights, several strategies for improving the low-temperature activity of Cu-SSZ-13 are proposed. Finally, the review offers a perspective on the future of low-temperature SCR of NO_x over Cu-SSZ-13.