Electrocatalytic N Reduction on FeS Nanoparticles Embedded in Graphene Oxide in Acid and Neutral Conditions.

The development of stable, low-cost, and highly efficient electrocatalysts for the N reduction reaction (NRR) process is challenging but crucial for ammonia production. Herein, we demonstrate the synthesis of pyrite nanoparticles wrapped by graphene oxide (FeS@GO) acting as a highly efficient NRR catalyst in a wide pH range. The FeS 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 N reduction over the FeS@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 N forming *NNH species as the potential-determining step is as low as 0.93 eV in N electroreduction. The electrochemical test results reveal that, as expected, FeS@GO exhibits high Faradaic efficiencies (4.7% in 0.1 M HCl solution and 6.8% in 0.1 M NaSO solution) and advanced NH yields (78.6 and 27.9 μg h mg in 0.1 M HCl and 0.1 M NaSO 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.