Operando analysis reveals potential- driven in situ formation of single- Fe- atom electrocatalysts for green production of ammonia

As a sustainable approach for N-2 fixation, electrocatalytic N-2 reduction reaction (N2RR) to produce ammonia (NH3) is highly desirable with a precise understanding to the structure-activity relationship of electrocatalysts. Here, firstly, we obtain a novel carbon-supported oxygen-coordinated single -Fe -atom catalyst for highly efficient pro-duction of ammonia from electrocatalytic N2RR. Based on such new type of N2RR electrocatalyst, by combining operando X -ray absorption spectra (XAS) with density function theory calculation, we reveal significantly that the as-prepared active coor-dination structure undergoes a potential-driven two -step restructuring, firstly from FeSAO(4)(OH)1a to FeSAO(4)(OH)1a & PRIME;(OH)1b with the adsorption of another -OH on FeSA at open-circuit potential (OCP) of 0.58 VRHE, and subsequently restructuring from FeSAO4(OH)1a(OH)1b to FeSAO3(OH)1a & DPRIME; due to the breaking of one Fe -O bond and the dissociation of one -OH at working potentials for final electrocatalytic process of N2RR, thus revealing the first potential-induced in situ formation of the real electrocatalytic active sites to boost the conversion of N-2 to NH3. Moreover, the key intermediate of Fe-NNHx was detected experimentally by both operando XAS and in situ attenuated total reflection-surface-enhanced infrared absorption spectra (ATR-SEIRAS), indicating the alternating mechanism followed by N2RR on such catalyst. The results indicate the necessity of considering the potential-induced restructuring of the active sites on all kinds of electrocatalysts for such as highly efficient ammonia production from N2RR. It also paves a new way for a precise understanding to the structure-activity relationship of a catalyst and helps the design of highly efficient catalysts.