Operando analysis reveals potential-driven in situ formation of single-Fe-atom electrocatalysts for green production of ammonia.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 37307468.
- Also identified by DOI 10.1073/pnas.2301011120 and PMC identifier 10288616.
- Licence recorded as CC BY-NC-ND.
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Abstract
As a sustainable approach for N<sub>2</sub> fixation, electrocatalytic N<sub>2</sub> reduction reaction (N<sub>2</sub>RR) to produce ammonia (NH<sub>3</sub>) 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 production of ammonia from electrocatalytic N<sub>2</sub>RR. Based on such new type of N<sub>2</sub>RR electrocatalyst, by combining operando X-ray absorption spectra (XAS) with density function theory calculation, we reveal significantly that the as-prepared active coordination structure undergoes a potential-driven two-step restructuring, firstly from Fe<sub>SA</sub>O<sub>4</sub>(OH)<sub>1a</sub> to Fe<sub>SA</sub>O<sub>4</sub>(OH)<sub>1a'</sub>(OH)<sub>1b</sub> with the adsorption of another -OH on Fe<sub>SA</sub> at open-circuit potential (OCP) of 0.58 V<sub>RHE</sub>, and subsequently restructuring from Fe<sub>SA</sub>O<sub>4</sub>(OH)<sub>1a'</sub>(OH)<sub>1b</sub> to Fe<sub>SA</sub>O<sub>3</sub>(OH)<sub>1a″</sub> due to the breaking of one Fe-O bond and the dissociation of one -OH at working potentials for final electrocatalytic process of N<sub>2</sub>RR, thus revealing the first potential-induced in situ formation of the real electrocatalytic active sites to boost the conversion of N<sub>2</sub> to NH<sub>3</sub>. Moreover, the key intermediate of Fe-NNH<sub>x</sub> was detected experimentally by both <i>operando</i> XAS and in situ attenuated total reflection-surface-enhanced infrared absorption spectra (ATR-SEIRAS), indicating the alternating mechanism followed by N<sub>2</sub>RR 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 N<sub>2</sub>RR. 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.