Vacancy Engineering of Iron-Doped W₁₈ O₄₉ 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 NH₃ formation rate and high Faradic efficiency (FE) difficult. To give effective NRR electrocatalysis and suppressed HER, the surface atomic structure of W₁₈ O₄₉ , which has exposed active W sites and weak binding for H₂ , is doped with Fe. A high NH₃ 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 W₁₈ O₄₉ crystal structure, which increases the oxygen vacancies and exposes more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR.