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

Abstract Electrocatalytic nitrate (NO 3 − ) reduction to ammonia (NH 3 ) is a green and efficient NH 3 synthesis technology. Metallic silver (Ag) is one of the well‐known electrocatalysts for NO 3 − reduction. However, under alkaline conditions, its poor water‐splitting ability fails to provide sufficient protonic hydrogen required for NH 3 synthesis, resulting in low NH 3 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 NH 3 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 NH 3 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.