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 WSe2-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 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 WSe2-x in 12 m LiClO4, which is among the highest NRR performances reported to date.
Keywords: density functional theory calculations; electrocatalytic reduction reaction; in situ spectroscopy; molecular dynamics simulations; water-in-salt electrolytes.