Boosting nitrate electroreduction to ammonia via in situ generated stacking faults in oxide-derived copper

Electrochemical reduction of nitrate is a promising approach to the production of value-added ammonia, which is meaningful in wastewater remediation and energy saving. However, the structural changes of metal oxide electrocatalysts have not fully understood under the electrocatalytic nitrate reduction reaction (NO3RR). Here, we find that the pristine Cu oxides can be transformed into Cu (oxide-derived Cu) with a high density of stacking faults during NO3RR process. The oxide-derived Cu directly grown on Cu foam produces great nitrate-N removal, ammonia-N selectivity, and ammonia Faradaic efficiency up to 93, 94, and 80%, respectively. Physical characterizations and theoretical investigations indicate that the oxide-derived Cu with in situ generated stacking faults causes tensile strain, which is favorable for nitrate adsorption and makes the metallic Cu more active. This work offers a new strategy of altering the electrocatalyst properties by in situ generating stacking faults from its oxides during nitrate reduction.