Sulfur vacancy MoS2 for electrocatalytic reduction of nitrate to ammonia with enhanced selectivity

As an important raw material, ammonia consumes a significant amount of the world's energy. The electrocatalytic reduction of nitrate to ammonia provides a new way to generate NH3 from waste water under benign conditions. However, NO3- conversion toward N2 and H2 evolution reaction (HER) competition limit the development of nitrate reduction to ammonia. In this study, we synthesized MoS2 with sulfur vacancies (SVs) using a one-step hydrothermal method, and we used the SVs to utilize the H* from the side reaction HER and accelerate the process of *N to NH3. MoS2 with SVs exhibits higher ammonia synthesis performance and faradaic efficiency (FE) than that of MoS2, with ammonia yield enhancing from 76.67 mu g h-1 mgcat. -1 to 111.33 mu g h-1 mgcat. -1 and FE expanding from 44.62 % to 78.04 % at - 0.6 V vs. RHE at ambient conditions. Calculations using density functional theory discovered that the presence of SVs effectively lowered the energy barrier in the potential-determining step for nitrate reduction, and H* couples with nearby *N at Mo sites promote activity. This research enhances our knowledge of how to handle the content of MoS2 with SVs when preparing monolayered MoS2 with special catalytic properties.

Automated summary

The electrocatalytic reduction of nitrate to ammonia offers a new way to generate ammonia from waste water, but the competition between nitrate conversion and hydrogen evolution reaction (HER) limits its development. This study synthesized MoS2 with sulfur vacancies (SVs) and used these SVs to promote the production of ammonia. MoS2 with SVs showed higher ammonia synthesis performance and faradaic efficiency. The research enhances our understanding of how to handle the content of MoS2 with SVs when preparing monolayered MoS2 with special catalytic properties.