Electron-Pump Driven Redox Design for Boosting the Reactivity of Ceria

Abstract

Electron-pump behavior can enhance charge transfer and redox cycling in heterogeneous catalysis, but its dynamic evolution under reaction conditions is difficult to control. Herein, we incorporate Nb5+ into the CeO2 lattice via a two-step synthesis to act as a donor dopant that functions as an electron-pumping agent, tuning electron transfer and stabilizing the Ce3+/Ce4+ redox cycle. Nb5+ doping promotes Ce3+ formation and accelerates reversible Ce3+/Ce4+ cycling, which leads to improved activity, selectivity, and stability of CeO2 for the ammonia selective catalytic reduction reaction. In situ spectroscopy measurements reveal that accelerated electron cycling stimulates the activation of a variety of molecules, including complexes of O-2, NO, and NH3. The optimized Ce0.8Nb0.2O2 catalyst achieves >98% NO conversion and >98% N-2 selectivity from 200 to 400 degrees C and exhibits excellent H2O and SO2 resistance. This work establishes a clear structure-activity relationship centered on electron-pump function reinforcement and offers mechanistic insight into controlling the dynamic electron-transfer evolution during the catalytic reaction.