Dynamic Binuclear Cu II Sites in the Reduction Half-Cycle of Low-Temperature NH 3 –SCR over Cu-CHA Catalysts

作者：Wenshuo Hu, Federica Gramigni, Nicole Daniela Nasello, Nicola Usberti, Umberto Iacobone, Shaojun Liu, Isabella Nova, Xiang Gao, Enrico Tronconi · 发表于：ACS Catalysis · 年份：2022 · DOI：10.1021/acscatal.2c01213 · 被引用次数：58 · 研究领域：Catalytic Processes in Materials Science、Electrocatalysts for Energy Conversion、Nanomaterials for catalytic reactions

As the state-of-the-art catalyst for the selective catalytic reduction (SCR) of NOx from lean-burn engines, Cu-exchanged chabazite zeolite (Cu-CHA) has been a spotlight in environmental catalysis because of its preeminence in DeNOx performance and hydrothermal stability. The microscopic cycling of active Cu cations between Cu-II and Cu-I in response to dynamic, macroscopic reaction conditions dominates SCR catalysis over Cu-CHA zeolites. In such cycling, Cu cations are solvated by gas-phase reactants, e.g., NH3, under low-temperature (LT) conditions, conferring peculiar mobility to Cu-NH3 complexes and making them act as mobilized entities during LT-SCR turnovers. Such motions provide LT-SCR-a typical heterogeneous catalytic process-with homogeneous features over Cu-CHA, but, differently from conventional homogeneous catalysis, the motions are tethered by electrostatic interactions between Cu cations and conjugate Al centers. These features affect distinctly the LT-SCR redox chemistry on Cu-CHA, resulting in, for example, the involvement of two Cu-I-diamines in activating O-2 and reoxidizing Cu-I to Cu-II (oxidation half-cycle, OHC). The kinetically relevant reduction half-cycle (RHC) that reduces Cu ll to Cu l is far less understood particularly within the context of such linked homo- and heterogeneous catalysis. Here, we focus on the LT-RHC chemistry over Cu-CHA and summarize observations from a series of recent, dedicated works from our group, benchmarking these findings a...