Abstract
The possible phase transformation of catalysts under reaction conditions brings lots of difficulties in establishing the active phase.Herein,we report a hidden active phase over iron catalyst uniquely for the dehydrogenation of ammonia(NH3).The highest dehydrogenation rate corresponds to an evanescent Fe/Fe4N mixing phase while the nitrogen(N)kept on accumulating and gradually deactivated the catalyst.Density functional theory(DFT)calculations demonstrated that deposition of an N on Fe(100)surface modifies the electronic structure of its surrounding iron atoms,causing a significant reduction of the initial dehydrogenation barrier of NH3.To recover the hidden active phase,ambient-pressure double dielectric barrier discharge(DDBD)plasma was applied to the reaction system in situ to remove the excessive surface N,which yields a pronounced improvement of the catalytic performance.The work demonstrates that hidden active phase in thermal catalysis can be unfolded when the rate-determining step is subdued by applied plasma.
NSTL