Vacancy Engineering of Iron‐Doped W 18 O 49 Nanoreactors for Low‐Barrier Electrochemical Nitrogen Reduction

The electrochemical nitrogen reduction reaction (NRR) is a promising energy‐efficient and low‐emission alternative to the traditional Haber–Bosch process. Usually, the competing hydrogen evolution reaction (HER) and the reaction barrier of ambient electrochemical NRR are significant challenges, making a simultaneous high NH 3 formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W 18 O 49 , which has exposed active W sites and weak binding for H 2 , is doped with Fe. A high NH 3 formation rate of 24.7 μg h −1  mg cat −1 and a high FE of 20.0 % are achieved at an overpotential of only −0.15 V versus the reversible hydrogen electrode. Ab initio calculations reveal an intercalation‐type doping of Fe atoms in the tunnels of the W 18 O 49 crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.