Nickel-based dual single atom electrocatalysts for the nitrate reduction reaction.

Electrochemical nitrate (NO) reduction reaction (NORR) to ammonium (NH) or nitrogen (N) provides a green route for nitrate remediation. However, nitrite generation and hydrogen evolution reactions hinder the feasibility of the process. Herein, dual single atom catalysts were rationally designed by introducing Ag/Bi/Mo atoms to atomically dispersed NiNC moieties supported by nitrogen-doped carbon nanosheet (NCNS) for the NORR. Ni single atoms loaded on NCNS (Ni/NCNS) tend to reduce NO to valuable NH with a high selectivity of 77.8 %. In contrast, the main product of NORR catalyzing by NiAg/NCNS, NiBi/NCNS, and NiMo/NCNS was changed to N, giving rise to N selectivity of 48.4, 47.1 and 47.5 %, respectively. Encouragingly, Ni/NCNS, NiBi/NCNS, and NiAg/NCNS showed excellent durability in acidic electrolytes, leading to nitrate conversion rates of 70.3, 91.1, and 93.2 % after a 10-h reaction. Simulated wastewater experiments showed that NiAg/NCNS could remove NO up to 97.8 % at -0.62 V after 9-h electrolysis. This work afforded a new strategy to regulate the reaction pathway and improve the conversion efficiency of the NORR via engineering the dual atomic sites of the catalysts.