High-Efficiency N₂ Electroreduction Enabled by Se-Vacancy-Rich WSe_2- in Water-in-Salt Electrolytes

Electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable NH₃ production, while developing the NRR electrocatalysis systems with both high activity and selectivity remains a significant challenge. Herein, we combine catalyst and electrolyte engineering to achieve a high-efficiency NRR enabled by a Se-vacancy-rich WSe_2- catalyst in water-in-salt electrolyte (WISE). Extensive characterizations, theoretical calculations, and in situ X-ray photoelectron/Raman spectroscopy reveal that WISE ensures suppressed H₂ evolution, improved N₂ affinity on the catalyst surface, as well as an enhanced π-back-donation ability of active sites, thereby promoting both activity and selectivity for the NRR. As a result, an excellent faradaic efficiency of 62.5% and NH₃ yield of 181.3 μg h^-1 mg^-1 is achieved with WSe_2- in 12 m LiClO₄, which is among the highest NRR performances reported to date.