Vacancy Engineering of Fe-doped W18O49 Nanoreactors for Low-barrier Electrochemical Nitrogen Reduction.

Electrochemical nitrogen reduction reaction (NRR) is a promising energy-efficient and low-emission alternative to the traditional Haber-Bosch method. Usually, the competing hydrogen evolution reaction (HER) and reaction barrier of ambient electrochemical NRR are most significant challenges, making the simultaneous achievement of a high NH 3 yielding rate and a high Faradic efficiency (FE) extremely difficult for NRR. To address this issue, W 18 O 49 , with exposed W sites and intrinsically weak binding for H 2 , is doped by Fe to modify its surface atomic structure for effective NRR electrocatalysis and suppressed HER. On it, a high NH 3 yielding rate of 24.7 μg h -1  mg -1 cat.  and a high FE of 20.0% have been simultaneously gained at a very low overpotential of -0.15 V vs. reversible hydrogen electrode. Ab initio reveals an intercalation-type doping of Fe atoms in the tunnels of the W 18 O 49 crystal structure, which increases the oxygen vacancies for exposing more W active sites, optimizes the nitrogen adsorption energy, and facilitates the electrocatalytic NRR. Thus, this work will provide a rational design of electrocatalysts for various electrochemical processes.