Synergistic Cu-Co dual sites on self-supporting carbon nanotube/carbon cloth composites for efficient electrocatalytic nitrate reduction to ammonia

Abstract Electrocatalytic nitrate reduction to ammonia (NO 3 RA) has attracted considerable interest owing to its potential for nitrogen resource conversion and energy storage under mild conditions. However, this process still faces challenges such as low ammonia selectivity and poor catalyst stability. In this work, a series of m-CuO/Co 3 O 4 bimetallic oxide electrocatalysts supported on self-supporting carbon nanotube/carbon cloth composites (CNTC) were prepared and their NO 3 RA performance was systematically investigated. A significant synergistic effect exists between the Cu and Co dual active sites: Cu species adsorb and activate NO 3 − to NO 2 − , while Co species provide active hydrogen (H*) and promote the further reduction of NO 2 − to NH 3 . In the CuO/Co 3 O 4 composite, the two components may synergistically influence the electronic structure, thereby avoiding the issues of Cu‐induced excessive nitrite adsorption leading to catalyst deactivation, as well as Co‐induced low intrinsic activity and severe competing hydrogen evolution. Furthermore, the CNTC support can promote the dispersion of active components, expose more active sites, and improve ammonia synthesis efficiency. The optimized 0.67-CuO/Co 3 O 4 @CNTC catalyst achieves a maximum Faradaic efficiency of 91.2% for NH 3 at −0.4 V vs reversible hydrogen electrode, along with an ammonia yield rate of 17.54 mg·h −1 ·mgcat −1 , while keeping the nitrite concentration at a relatively low level and exhibiting excellent cycling stability. Overall, this study provides insights into the possible synergistic mechanism of multi-active sites and offers a design strategy and experimental foundation for developing highly active, well-dispersed, and stable NO 3 RA electrocatalysts.