Boosting electrochemical nitrogen reduction to ammonia with high efficiency using a LiNb3O8 electrocatalyst in neutral media

Abstract

The nitrogen reduction reaction (NRR) has great potential as a method to replace the industrial Haber–Bosch process for ammonia synthesis. Nevertheless, the efficiency of the NRR is mainly dependent on the rational design of highly efficient and active electrocatalysts on account of the high energy of N₂ and HER as a competitive reaction. Herein, a simple solid-phase synthesis method is adopted to design and synthesize a LiNb₃O₈ (LNO) electrocatalyst, which proves that the synergistic effect of electron-rich Nb and Li elements can effectively improve the NRR activity of commercial Nb₂O₅ and Li₂CO₃. The resultant LNO electrocatalyst presents an ammonia yield rate of 7.85 μg h⁻¹ mg_cat.⁻¹ with a faradaic efficiency of 82.83% at −0.4 V vs. RHE under ambient conditions, which are much higher than those of commercial Nb₂O₅ (1.67 μg h⁻¹ mg_cat.⁻¹, 13.51%) and Li₂CO₃ (1.93 μg h⁻¹ mg_cat.⁻¹, 8.41%). Detailed characterizations demonstrate that the obtained LNO electrocatalyst has a larger specific surface area of electrochemical activity and more active sites to promote the activity of the NRR. Moreover, the synergistic effect of Li and Nb elements greatly improves the hydrophobicity of the material, which is more conducive to the occurrence of the NRR. This work highlights the enormous potential of the LNO electrocatalyst with a hydrophobic surface and easy activation of NN for highly efficient ammonia synthesis under ambient conditions.