Enhanced Electrochemical Reduction of N₂ to Ammonia over Pyrite FeS₂ with Excellent Selectivity

Abstract

Electrochemical reduction of N2 reaction (NRR) into NH3 promises a sustainable and environmentally friendly technology at ambient temperature. However, high energy barrier and the competition with the hydrogen evolution reaction result in poor NH3 yield and low faradaic efficiency (FE) of NRR. Herein, the FeS2 catalyst was synthesized via a one-step hydrothermal method for NRR. In the N2-saturated Na2SO4 electrolyte, this catalyst exhibited superior catalytic performance to achieve a high NH3 yield (37.2 μg h–1 mgcat. –1) and FE (11.2%) with high stability and selectivity at −0.5 V versus the reversible hydrogen electrode, outperforming other NRR catalysts. According to experimental results, a preferable associative distal pathway was proposed. Density functional theory calculations revealed that the NRR process can proceed preferably on Fe atoms instead of S atoms, and the conversion of *NH2 to *NH3 was the potential-determining step with an energy barrier of 0.45 eV. Therefore, this work offers a new avenue to prepare high-efficiency and highly selective transition-metal-based catalysts for NRR under ambient conditions.

Defect and interface engineering in metal sulfide catalysts for the electrocatalytic nitrogen reduction reaction: a review

“…Therefore, the NRR performance of FeS 2 was investigated by Du and coworkers in a recent study, where FeS 2 nanoparticles were synthesized via hydrothermal reaction using FeSO 4 , Na 2 S 2 O 3 and sublimed sulfur as the precursors. 71 The electron spin resonance (ESR) spectrum indicated that lots of S vacancies existed in the FeS 2 and the FeS 2 exhibited an NH 3 yield of 37.2 μg h −1 mg cat −1 with a FE of 11.2% in 0.1 M Na 2 SO 4 at −0.5 V (Fig. 5B).…”

Fe‐based catalysts for nitrogen reduction toward ammonia electrosynthesis under ambient conditions

“…(E) Distal mechanism of the NRR catalyzed by FeS 2 . Reproduced with permission 53 . Copyright 2020, American Chemical Society.…”

“…Furthermore, the chrono‐potentiometric response shows a negligible decrease for 20 h consecutive electrolysis, with a 92.8% retention of the initial NH 3 yield (Figure 6C), indicating excellent long‐term stability. Gong et al 53 . demonstrated an FeS 2 NRR catalyst synthesized via a one‐step hydrothermal method.…”

Synthetic control over polymorph formation in the d-band semiconductor system FeS2

“…oxygen and hydrogen evolution reactions 18,19,30 or reduction of N 2 to ammonia. 31 Previous physical properties measurements on the naturally occurring marcasite have indicated that both polymorphs may have similar electronic and mechanical properties, making also marcasite a promising candidate for various narrow band-gap applications. 32,33 So far, studies on marcasite were restricted by the unavailability of high-quality and phase-pure samples, especially the preparation of high-quality single crystals under controlled conditions.…”