Fe foam supported FeVO ₄ nanoparticles for electrochemical nitrogen fixation at ambient conditions

Abstract

As global energy demand continues to rise with fossil fuels dwindling at a faster rate, posing energy and environmental concerns, there is a growing interest in exploring alternative, green, and renewable energy sources. Ammonia is a key hydrogen energy carrier and precursor to many value-added products, and the efforts for its generation at commercial scale using greener methods are intensifying to mitigate the reliance on the energy-intensive Haber-Bosch process. The electrochemical nitrogen reduction reaction (e-NRR) is a highly promising way of synthesizing ammonia under energy-efficient, green, and ambient conditions. Despite its attractive potential, the activity and efficiency of conventional eNRR catalysts are still a major concern due to low selectivity and poor ammonia yields. Inspired by the FeFe and FeV cofactors present in nitrogenases, this study reports the synthesis and electrocatalytic evaluation of FeVO₄ catalyst for N₂ reduction. The FeVO₄ nanoparticles anchored on Fe foam (FF) could serve as an efficient electrocatalyst for the electrochemical nitrogen fixation, achieving a significant performance with highest NH₃ yield of 22.5 µg·h^–1·mg^–1 and Faradaic efficiency (FE) of 20.74% at –0.2 V_RHE in 0.1 M Na₂SO₄. The FeVO₄ electrocatalyst exhibited robust electrochemical stability for 24 h of operation at –0.2 V_RHE. The high catalytic performance originated from the synergistic interactions between Fe and V which serve as dual electron donation centers for effective e-NRR. Furthermore, the coupling interaction between FeVO₄ and FF support exposed abundant intrinsic active sites and facilitated beneficial charge transfer further inducing superior e-NRR activity. Density functional theory (DFT) computations disclosed that surface Fe atoms are the main active centers for eNRR which proceed via the alternating pathway.

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