Outstanding low-temperature performance for NH3-SCR of NO over broad Cu-ZSM-5 sheet with highly exposed a-c orientation

Abstract

Five ZSM-5-based catalysts with diverse zeolitic morphologies were prepared to experimentally investigate and computationally analyze the correlation between crystal plane and copper species. The types and numbers of copper species dispersed over Cu-ZSM-5 catalysts were emphatically determined to elucidate the structure-performance relationship of the Cu-ZSM-5 catalyst with broad sheet in the selective catalytic reduction (SCR) of NO by NH3. This study indicates that the broad Cu-ZSM-5 sheet exhibits outstanding low-temperature performance, achieving complete NOx removal at 250–550 °C. Operando X-ray absorption spectroscopy (XAS) experiments demonstrated this nanosheet catalyst has highly dispersed Cu2+ ions as key active sites, which are facilely solubilized by NH3 at low temperatures, further promoting rapid dynamic switching between Cu2+ and Cu+ species. And the density functional theory (DFT) calculations showed the Cu2+ forms a unique interaction with the [010] crystal plane, leading to a lower energy barrier of the rate-determining step, resulting in extraordinary NOx conversion.