Electrochemical Synthesis of Metasequoia‐Like Reduced Graphene Oxide Coated Cobalt‐Silver Catalyst for Stable and Efficient Electrocatalytic Nitrate Reduction to Ammonia

Electrocatalytic nitrate (NO₃ ^-) reduction to ammonia (NH₃) is a green and efficient NH₃ synthesis technology. Metallic silver (Ag) is one of the well-known electrocatalysts for NO₃ ^- reduction. However, under alkaline conditions, its poor water-splitting ability fails to provide sufficient protonic hydrogen required for NH₃ synthesis, resulting in low NH₃ selectivity. Additionally, metal catalysts are prone to leaching and oxidation during electrocatalysis, resulting in poor stability. Herein, cobalt (Co) into Ag (CoAg) catalyst is doped, which not only increases the NH₃ selectivity by 34.4%, but also reduces the reduction potential by 0.1 V. Meanwhile, reduced graphene oxide (rGO) as a protective "armor" is used to encapsulate the CoAg catalyst (rGO_2.92@CoAg). The rGO_2.92@CoAg catalyst shows excellent stability for over 300 hours (h) of continuous reaction. The Co and Ag contents in the rGO_2.92@CoAg catalyst after continuous tests decreases by only 4.3% and 3.1%, respectively, which are much lower than those of the CoAg catalyst without the rGO (90.8%, 52.6%). Moreover, the rGO_2.92@CoAg catalyst shows high Faradaic efficiency (99.3%) and NH₃ yield rate (1.47 mmol h^-1 cm^-2). Therefore, a high performance and strong stability rGO_2.92@CoAg catalyst is obtained by Co doping and rGO coating, which provides theoretical basis for practical industrial application.