Engineering sulfur vacancies optimization in Ni3Co6S8 nanospheres toward extraordinarily efficient nitrate electroreduction to ammonia.

Electrocatalytic nitrate reduction into recyclable ammonia (NH 3) plays a critical role in maintaining the global nitrogen balance and meeting the growing energy demand. However, the research on controllable defects of traditional semiconductor electrocatalytic materials remains lacking, resulting in limiting nitrate reduction reaction (NO 3 RR) activity. Herein, we develop a facile electrical joule heating method to flexibly regulate the sulfur vacancies (SVs) content on the surface of Ni 3 Co 6 S 8 (NCS), in which SVs can regulate the electronic structure of NCS. Therefore, more 3 d electrons can be localized at Co sites that can reduce the energy barrier of the rate-determining step (HNO 3 *→NO 2 *). As a result, the NCS with reasonable SVs concentration exhibits the outstanding selectivity (98.2%), Faradaic efficiency (85.3%) and yield rate (2388.4 μg h−1 cm−2) for electrocatalytic nitrate reduction to ammonia while maintaining their structural integrity. This work provides a new insight for addressing both nitrate pollution and ammonia energy production. [Display omitted] • Optimization of sulfur vacancies (SVs) on Ni 3 Co 6 S 8 (NCS) surface by electric joule heating method. • Sulfur vacancies can tune electronic structure and enhance the electrochemical activity of NCS. • A highly ammonia yield rate (2388.4 μg h−1 cm−2) and selectivity (98.2%) are obtained on the NCS with appropriate SVs. • The facilitated formation of NO 2 * by SVs is essential for improving the conversion of NO 3 - to NH 3. [ABSTRACT FROM AUTHOR]