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

Abstract Electrochemical route is an admirable strategy for N 2 fixation to NH 3 , 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 K 0.33 WO 3.16 (K‐WO 3 ) by molten salt method, then K 0.33 WO 3.16 with surface defect structure (WO 3 ‐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 WO 3 ‐OV gets improved to 25.45 % at −0.3 V (vs RHE), much superior to K‐WO 3 (FE: 9.33 %). It is worth noting that defect‐rich WO 3 ‐OV also shows high electrochemical stability.