Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu‐SSZ‐13

Abstract

Abstract Operando X‐ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu‐exchanged SSZ‐13. Catalysts prepared to contain only isolated, exchanged Cu II ions evidence both Cu II and Cu I ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH 3 together are necessary for Cu II reduction to Cu I . DFT calculations show that NO‐assisted NH 3 dissociation is both energetically favorable and accounts for the observed Cu II reduction. The calculations predict in situ generation of Brønsted sites proximal to Cu I upon reduction, which we quantify in separate titration experiments. Both NO and O 2 are necessary for oxidation of Cu I to Cu II , which DFT suggests to occur by a NO 2 intermediate. Reaction of Cu‐bound NO 2 with proximal NH 4 + completes the catalytic cycle. N 2 is produced in both reduction and oxidation half‐cycles.