Dendritic Copper Oxide Catalyst Engineering Weak-polarity Cu-O Bond for High-efficiency Nitrate Electroreduction

Nitrate reduction reaction (NO3RR) is deemed a promising pathway for both ammonia synthesis and water purification. Developing a high-efficiency catalyst with excellent NH3 selectivity and catalytic stability is desirable but remains challenging. In this work, a dendritic copper oxide catalyst (Cu-B2) has been developed to efficiently catalyze NO3RR for ammonia production, the Cu-B2 exhibits excellent catalytic performance, achieving an NH3 Faradaic efficiency as high as 94% and an NH3 yield of 16.9mgh-1 cm-2 with a current density of 192.3mAcm-2 at -0.6V (vs. RHE, reversible hydrogen electrode). During NO3RR testing, the Cu-B2 catalysts are reduced in situ to form highly active Cu0/Cu+ sites, while retaining its dendritic morphology. Compared with other catalysts, the Cu-O bond in Cu-B2 catalyst has weaker polarity, resulting in Cu0/Cu+ sites in lower oxidation states. In situ attenuated total reflection surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies reveal the Cu-B2 catalyst exhibits a potential-independent capability for ⁎NO3- adsorption and high conversion efficiency of NO2- intermediate into ammonia, DFT calculations reveal that Cu-B2 exhibts higher NO3- adsorption energy and lower NO3- adsorption energy barrier than Cu-B1, thus endowing it with a remarkably improved catalytic activity and durability. Environmental Implication Nitrate (NO3-) in drinking water can be converted by mammals into carcinogen nitrite (NO2-), which causes birth defects and thyroid disease. Thus, there is an urgent need for efficient nitrate removal technologies suitable for large-scale or household water treatment. In this work, a Cu-B2 catalyst has been developed to highly selectively convert NO3- into the valuable NH3 product. The high-efficiency nitrate reduction catalyzed by the Cu-B2 catalyst is expected to mitigate the detrimental effect of nitrate on the environment in the future. Moreover, it offers an alternative pathway for NH3 production to the traditional Haber-Bosch process.