Ru-Doped NiFe-MIL-53 with Facilitated Reconstruction and Active Hydrogen Supplement for Enhanced Nitrate Reduction.

The Electrochemical reduction of nitrate to ammonia (NH) is a process of great significance to energy utilization and environmental protection. However, it suffers from sluggish multielectron/proton-involved steps involving coupling reactions between different reaction intermediates and active hydrogen species (H) produced by water decomposition. In this study, a Ru-doped NiFe-MIL-53 (NiFeRu-MIL-53) supported on Ni foam (NF) has been designed for the nitrate reduction reaction (NORR). The NiFeRu-MIL-53 exhibits excellent NORR activity with a maximum Faradaic efficiency (FE) of 100% at -0.4 V vs. RHE for NH and a maximum NH yield of 62.39 mg h cm at -0.7 V vs. RHE in alkaline media. This excellent performance for the NORR is attributed to a strong synergistic effect between Ru and reconstructed NiFe(OH). Additionally, the doped Ru facilitates water dissociation, leading to an appropriate supply of H required for N species hydrogenation during NORR, thereby further enhancing its performance. Furthermore, in situ Raman analysis reveals that incorporating Ru facilitates the reconstruction of MOFs and promotes the formation of hydroxide active species during the NORR process. This work provides a valuable strategy for designing electrocatalysts to improve the efficiency of the reduction of electrochemical nitrate to ammonia.