WO3 Rich in Oxygen Vacancies Through Ion-Exchange Reaction for Enhanced Electrocatalytic N2 Reduction to NH3

Electrochemical route is an admirable strategy for N-2 fixation to NH3, which can save more energy and reduce greenhouse gas emissions compared with the Haber-Bosch process. However, it still suffers from extremely low ammonia yield for the lack of effective electrocatalysts and shows low Faraday efficiency due to competitive hydrogen evolution reaction (HER). Herein, we firstly synthesized needle-like K0.33WO3.16 (K-WO3) by molten salt method, then K0.33WO3.16 with surface defect structure (WO3-OV) was successfully obtained through ion-exchange of H+ and dehydration process. An obvious absorption enhancement in the near infrared region exhibited in UV-vis absorption spectra and a significant ESR signal at g=2.003 proves the existence of O vacancies. The abundant oxygen vacancies ensure that Faraday efficiency of WO3-OV gets improved to 25.45 % at -0.3 V (vs RHE), much superior to K-WO3 (FE: 9.33 %). It is worth noting that defect-rich WO3-OV also shows high electrochemical stability.

Automated summary

Electrochemical route is a promising strategy for N-2 fixation to NH3, with more energy-saving and reduced greenhouse gas emissions compared to the Haber-Bosch process. However, the lack of effective electrocatalysts leads to low ammonia yield and low Faraday efficiency. By synthesizing needle-like K0.33WO3.16 (K-WO3) and obtaining surface defect structure WO3-OV, the Faraday efficiency of WO3-OV is significantly improved to 25.45% at -0.3 V, with high electrochemical stability.