Electrocatalytic N₂ Reduction on FeS₂ Nanoparticles Embedded in Graphene Oxide in Acid and Neutral Conditions

The development of stable, low-cost, and highly efficient electrocatalysts for the N₂ reduction reaction (NRR) process is challenging but crucial for ammonia production. Herein, we demonstrate the synthesis of pyrite nanoparticles wrapped by graphene oxide (FeS₂@GO) acting as a highly efficient NRR catalyst in a wide pH range. The FeS₂ nanoparticles are uniformly dispersed across the GO nanosheet, thus leading to the fine exposure of active sites, the promotion of charge transfer, and the increment of a contact surface area, which are all beneficial for a desired catalyst. In the meantime, the low-coordinated Fe atoms are activated as highly active sites, which is in favor of the enhanced electrochemical performance for the NRR. Furthermore, density functional theory (DFT) calculations illustrated that the high activity of N₂ reduction over the FeS₂@GO catalyst arises from the well-exposed Fe active sites and the increment of charge density at the valence band edge. Benefiting from the well-optimized interface, the barrier of the addition of the first hydrogen atom to N₂ forming *NNH species as the potential-determining step is as low as 0.93 eV in N₂ electroreduction. The electrochemical test results reveal that, as expected, FeS₂@GO exhibits high Faradaic efficiencies (4.7% in 0.1 M HCl solution and 6.8% in 0.1 M Na₂SO₄ solution) and advanced NH₃ yields (78.6 and 27.9 μg h^-1 mg_cat.^-1 in 0.1 M HCl and 0.1 M Na₂SO₄ solutions, respectively) in both acid and neutral conditions. This work offers a new avenue for exploring novel electrocatalysts, which has great promise to accelerate the practical application of the NRR.