Facile, cost-effective plasma synthesis of self-supportive FeSx on Fe foam for efficient electrochemical reduction of N2 under ambient conditions
The electrochemical N2 reduction reaction (NRR) in an aqueous medium has recently aroused great attention for the synthesis of NH3 under ambient conditions. However, this process generally suffers from a low NH3 production rate and often requires a noble-metal based electrocatalyst with some sophisticated nanosynthesis method. This work reports a new non-precious, self-supportive iron sulfide (FeSx) NRR electrocatalyst, synthesized by a simple H2S-plasma treatment on low-cost Fe foam. The H2S-plasma treatment sulfurizes the Fe surface to afford a self-supportive FeSx thin layer on the Fe foam (FeSx/Fe). The synthesized FeSx/Fe foam can be directly used as the electrode for the NRR, and it is demonstrated to show a remarkable NH3 production rate of 4.13 × 10−10 mol s−1 cm−2 and a high faradaic efficiency of 17.6%, significantly outperforming many other reported non-precious electrocatalysts. Further material characterization shows that the surface FeSx converts to the mackinawite FeS after the NRR; the mackinawite FeS is possibly the actual high-activity NRR electrocatalyst, and density functional theory calculation is further employed to elucidate the NRR mechanism. Given the high performance and low cost, we envision that the plasma-synthesized FeSx/Fe will be of great promise for the electrochemical NH3 synthesis under ambient conditions.