The Electrochemical reduction of nitrate to ammonia (NH3) 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 (Hads) 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 (NO3RR). The NiFeRu-MIL-53 exhibits excellent NO3RR activity with a maximum Faradaic efficiency (FE) of 100% at −0.4 V vs. RHE for NH3 and a maximum NH3 yield of 62.39 mg h–1 cm–2 at −0.7 V vs. RHE in alkaline media. This excellent performance for the NO3RR is attributed to a strong synergistic effect between Ru and reconstructed NiFe(OH)2. Additionally, the doped Ru facilitates water dissociation, leading to an appropriate supply of Hads required for N species hydrogenation during NO3RR, 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 NO3RR process. This work provides a valuable strategy for designing electrocatalysts to improve the efficiency of the reduction of electrochemical nitrate to ammonia.
Designing highly active and stable electrocatalysts of oxygen evolution reaction (OER) is one of the crucial challenges. In this study, a novel OER electrocatalyst, NiFe-MIL-53 modified with ultra-low rhodium (Rh@NiFe-MIL-53), is successfully prepared via the hydrothermal method. In-situ Raman spectroscopy and electrochemical impedance spectroscopy reveal that the doped Rh accelerates the phase transformation of NiFe-MIL-53 and the in-situ formed Rh@NiFeOOH is the actual active species. More importantly, the enhanced reversibility of electrochemical reconstruction between NiFeOOH and NiFe(OH) 2 after doping Rh is beneficial for improving the electrochemical stability of the catalyst. X-ray photoelectron spectroscopy spectra show the strong electronic interaction between single-atom Rh and Ni/Fe in Rh@NiFeOOH. Furthermore, theoretical calculations confirm that the integration of single-atom Rh into the NiFeOOH successfully reduces the band gap, regulates the d -band center ( ε d ), accelerates the charge transfer, and optimizes the adsorption behavior of oxygen-containing intermediates, thereby lowering the energy barrier of rate-determining steps. Consequently, the optimized Rh@NiFe-MIL-53 exhibits excellent OER activity (240 mV) with a small Tafel slope of 48.2 mV dec −1 and long-term durability (over 1270 h at 10 mA cm −2 and 110 h at 200 mA cm −2 ). This work presents a new perspective on designing highly efficient OER electrocatalysts.
危险品化学品经营许可证（带存储）