High-Efficiency N 2 Electroreduction Enabled by Se-Vacancy-Rich WSe 2- x in Water-in-Salt Electrolytes.

Electrocatalytic nitrogen reduction reaction (NRR) is a promising approach for renewable NH 3 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- x catalyst in water-in-salt electrolyte (WISE). Extensive characterizations, theoretical calculations, and in situ X-ray photoelectron/Raman spectroscopy reveal that WISE ensures suppressed H 2 evolution, improved N 2 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 NH 3 yield of 181.3 μg h -1 mg -1 is achieved with WSe 2- x in 12 m LiClO 4 , which is among the highest NRR performances reported to date.