Atomic-Level Dispersed Cu in NiFe–LDH Hollow Nanocages for Highly Efficient Electrochemical Nitrate Reduction Reaction

Electrochemical nitrate reduction reaction (eNO3–RR) is considered to be a method of killing two birds with one stone that could produce ammonia while removing nitrate pollutant, attracting wide attention in the field of catalysis and material science. eNO3–RR involves a complex eight-electron transfer process, and how to design a highly efficient catalyst has become one of the most important scientific challenges in related fields. A NiFe-layered double hydroxide with atomically dispersed Cu dopants in hollow nanocage morphology (CuNiFe–LDH HNCs) is successfully synthesized in the present study, and the catalyst exhibits high eNO3–RR activity in neutral solutions, achieving an ammonia formation rate at 3.58 mg h–1 cm–2 with a Faradaic efficiency of 90.1%, which is three times higher than that of the undoped sample. In addition, a Zn-nitrate battery system is developed that exhibits a power density of 9.8 mW cm–2 and durable discharge–charge cycle stability. The present work not only provides an LDH-type catalyst for a highly efficient eNO3–RR process and corresponding applications as a Zn-nitrate battery but also emphasizes the importance of proper adjustment of the electronic structure via a concept of heteroatom doping.