Cascade electrocatalytic nitrate reduction reaching 100% nitrate-N to ammonia-N conversion over Cu2O@CoO yolk-shell nanocubes

• Main Authors: Huang, Wenjing, Luo, Wenyu, Liu, Jiawei, Jia, Bei-Er, Lee, Carmen, Dong, Jinfeng, Yang, Lan, Liu, Bin, Yan, Qingyu
• Other Authors: School of Materials Science and Engineering
• Format: Article
• Language: English
• Published: 2024
• Subjects: Engineering; Ammonia synthesis; Cascade electrocatalysis
• Online Access: https://hdl.handle.net/10356/180927
• Institution: Nanyang Technological University

The electroreduction of nitrate to ammonia via a selective eight-electron transfer nitrate reduction reaction offers a promising, low energy consumption, pollution-free, green NH3 synthesis strategy alternative to the Haber-Bosch method. However, it remains a great challenge to achieve high NH4+ selectivity and complete conversion from NO3--N to NH4+-N. Herein, we report ingredients adjustable Cu2O@CoO yolk-shell nanocubes featured with tunable inner void spaces and diverse activity centers, favoring the rapid cascade conversion of NO3- into NO2- on Cu2O and NO2- into NH4+ on CoO. Cu2O@CoO yolk-shell nanocubes exhibit super NH4+ Faradaic efficiencies (>99%) over a wide potential window (-0.2 V to -0.9 V versus RHE) with a considerable NH4+ yield rate of 15.27 mg h-1 cm-2 and fantastic cycling stability and long-term chronoamperometric durability. Cu2O@CoO yolk-shell nanocubes exhibited glorious NO3--N to NH4+-N conversion efficiency in both dilute (500 ppm) and highly concentrated (0.1 and 1 M) NO3- electrolytes, respectively. The nitrate electrolysis membrane electrode assembly system equipped with Cu2O@CoO yolk-shell nanocubes delivers over 99.8% NH4+ Faradaic efficiency at cell voltages of 1.9-2.3 V.