Modulation strategies of Cu-based electrocatalysts for efficient nitrogen reduction

The electrochemical nitrogen reduction reaction (NRR) has attracted great attention recently for ammonia synthesis at ambient temperature and pressure and exhibits largely reduced energy consumption for ammonia production compared with the traditional Haber-Bosch process. The rational design and optimization of NRR electrocatalysts are critically important for breaking the triple bond between nitrogen atoms and the subsequent formation of the N-H bond. Cu-based materials have recently been developed as promising electrocatalysts by various morphology and electronic structure modulation strategies for efficient NRR thanks to the 3d transition metal structure, low cost, high reserves, and excellent catalytic performance of Cu. To further explore new possibilites in this area, in this review, the rational modulation of Cu-based electrocatalysts is used as a typical example to summarize various design strategies effectively enhancing the ammonia yield and conversion efficiency for the NRR. Following a brief presentation of the reaction mechanism of the NRR, five strategies for altering the structure and properties of Cu-based electrocatalysts, namely morphology modulation, alloy engineering, lattice phase regulation, vacancy engineering and single-atom structure construction, are comprehensively summarized and the relationship between the catalyst modulation and corresponding NRR performance is discussed. Finally, the current challenges and future perspectives of the NRR are presented.