Green NH3 production by direct electrocatalytic synthesis from N2 and H2O is still a challenging reaction, which requires us to better understand the nature of the active materials. We show here that iron oxide (Fe2O3) nanoparticles (supported over carbon nanotubes, CNTs) become more active than the corresponding samples after reduction to form Fe- or Fe2N-supported nanoparticles, both indicated as active species in the thermal catalytic reduction of N2 to ammonia. Characterization data, however, indicate that even for these Fe- and Fe2N−CNT samples, obtained from Fe2O3−CNT by reduction in H2 or NH3 at 500 °C, the active species responsible for N2 reduction reaction (NRR) at low applied potential (−0.5 V vs RHE) are the same, that is, small (<1–2 nm) iron oxide nanoparticles that are not detected by XRD, but evidenced by XPS and which amount could be correlated to the rate of ammonia formation. This species is stable for at least 24 h of electrocatalytic flow tests. However, at higher applied potentials, sintering/transformation of this species occurs, with loss of the electrocatalytic activity, and Fe2N nanoparticles may also be reduced in situ, forming ammonia, but with irreversible deactivation. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Direct Synthesis of Ammonia from N2 and H2O on Different Iron Species Supported on Carbon Nanotubes using a Gas-Phase Electrocatalytic Flow Reactor

Chen S
Primo
;
Perathoner S
Secondo
;
Ampelli C;Wei H;Abate S;Centi G.
Ultimo
2020-01-01

Abstract

Green NH3 production by direct electrocatalytic synthesis from N2 and H2O is still a challenging reaction, which requires us to better understand the nature of the active materials. We show here that iron oxide (Fe2O3) nanoparticles (supported over carbon nanotubes, CNTs) become more active than the corresponding samples after reduction to form Fe- or Fe2N-supported nanoparticles, both indicated as active species in the thermal catalytic reduction of N2 to ammonia. Characterization data, however, indicate that even for these Fe- and Fe2N−CNT samples, obtained from Fe2O3−CNT by reduction in H2 or NH3 at 500 °C, the active species responsible for N2 reduction reaction (NRR) at low applied potential (−0.5 V vs RHE) are the same, that is, small (<1–2 nm) iron oxide nanoparticles that are not detected by XRD, but evidenced by XPS and which amount could be correlated to the rate of ammonia formation. This species is stable for at least 24 h of electrocatalytic flow tests. However, at higher applied potentials, sintering/transformation of this species occurs, with loss of the electrocatalytic activity, and Fe2N nanoparticles may also be reduced in situ, forming ammonia, but with irreversible deactivation. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/3175149
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