Locking Copper Sites against Over-reduction at a CaSO4-Modified NiCu Interface for Durable Acetylene Semi-hydrogenation

Acetylene semi-hydrogenation is critical for industrial polymer-grade ethylene production. Copper-based catalysts can achieve high selectivity via Cu + /Cu 0 interfacial sites, yet excessive Cu + reduction under reaction conditions disrupts this balance, depletes active ensembles, and causes rapid deactivation. Current strategies show limited efficacy, and both the dynamic structural evolution and effective Cu + stabilization mechanisms remain unclear. Herein, we show that in situ formed CaSO 4 greatly boosts NiCu catalyst durability by stabilizing Cu + -rich interfacial sites and inhibiting Cu + over-reduction. A combination of in situ characterization techniques and density functional theory (DFT) calculations revealed the dynamic evolution of the Cu + / Cu 0 active sites and confirmed that CaSO 4 , interacting strongly with surface Cu species, effectively suppresses the reduction of Cu + by modulating Cu–O bonds. The optimized catalyst achieves an acetylene conversion of ∼98%, ethylene selectivity of >94%, and a deactivation rate constant of 4.52 × 10 –4 ± 6.16 × 10 –5 h –1 and maintains stable operation for 100 h. This work offers atomistic deactivation insights and proposes an interfacial electronic-structural stabilization strategy for durable semi-hydrogenation catalysts.