Cascade Electrocatalytic Reduction of Nitrate to Ammonia Using Bimetallic Covalent Organic Frameworks with Tandem Active Sites

Abstract Electrochemical nitrate reduction reaction (NO 3 RR) is a promising approach to simultaneously realize pollutant removal and ammonia generation. However, this process involves the transfer of eight electrons and nine protons along with multiple by‐products, resulting in a significant challenge for achieving high ammonia yield and selectivity. Herein, we introduced bimetallic covalent organic frameworks catalysts with Cu and Co active sites to achieve a two‐step tandem reaction, avoiding excessive nitrite accumulation and enabling efficient NO 3 RR. For the initial two‐electron process, the Cu sites in the bimetallic catalyst exhibit a strong binding affinity with nitrate, promoting their conversion to nitrite. The Co sites enhance the supply and adsorption of active hydrogen and stabilize the subsequent six‐electron process, thereby improving the overall catalytic efficiency. Compared to monometallic Cu and Co catalysts, the CuCo bimetallic catalyst demonstrates superior ammonia yield and Faradaic efficiency (NH 3 yield rate = 20.8 mg·h −1 ·cm −2 , FE = 92.16% in 0.3 M nitrate). Such coordinated two‐step process advances the efficiency and applicability of NO 3 RR through optimizing a cascade catalytic reaction, thereby establishing an innovative path for the engineering of NO 3 RR electrocatalysts.