Two-dimensional BCN matrix inlaid with single-atom-Cu driven electrochemical nitrate reduction reaction to achieve sustainable industrial-grade production of ammonia

• Published in: Applied materials today 2021-12, Vol.25, p.101206, Article 101206
• Main Authors: Zhao, Xue, Jia, Xiuxiu, He, Yingnan, Zhang, Haibo, Zhou, Xiaohai, Zhang, Hucai, Zhang, Shusheng, Dong, Yemin, Hu, Xun, Kuklin, Artem V., Baryshnikov, Glib V., Ågren, Hans, Hu, Guangzhi
• Format: Article
• Language: English
• Subjects: Electrocatalysis; Nitrate reduction; Nitrate removal; Single-atom Cu; Synthetic ammonia
• ISSN: 2352-9407; 2352-9415
• DOI: 10.1016/j.apmt.2021.101206

•Achieved the anchoring of single-atom Cu on the BCN through structural confinement engineering.•Ammonia yield rate reaches milligram level and the selectivity is as high as 97.37%.•Achieve high-efficiency and high-selectivity production of ammonia in the full-pH range.•BCN-Cu has strong electrochemical cycle stability and long-term durability. Electrochemical methods have been proven to effectively eliminate nitrates in sewage and convert them into high value-added ammonia products. Here, after annealing treatment of metal boron cluster organic polymers formed by the combination of 1,10-phenanthroline, Cu2+ and closo-[B12H12]2-, a Cu single-atom doped BCN (B-doped CN) with a diamond-shaped nanosheet structure was obtained. In the electrochemical reduction reaction of nitrate, BCN-Cu exhibits excellent catalytic activity, specifically: 1) the ammonia yield rate reached as high as 498.85 μg h−1 cm−2, 1047.14 μg h−1 cm−2, 1900.07 μg h−1 cm−2 and 3358.74 μg h−1 cm−2 at -0.3 V, -0.4 V, -0.5 V and -0.6 V vs reversible hydrogen electrode, respectively, and Faradaic efficiency is 95.90%, 97.28%, 98.23% and 97.37%; 2) after repeated use of BCN-Cu 10 times or continuous operation for 16 h, the activity against electrochemical reduction reaction of nitrate anions is almost unchanged. The 15NO3− isotopic labeling experiment proved that the detected NH3 comes from the reduction of NO3− on BCN-Cu. Control experiments show that the presence of Cu determines whether BCN-Cu has the possibility of catalyzing electrochemical reduction reactions of nitrate, and the presence of the B element enhances the catalytic activity of BCN-Cu. Density functional calculations indicate that in the water phase the process of reducing NO3− to NH3 on Cu0 is an exothermic reaction, and that the adsorption process of NO3− on Cu0 is the rate-determining step. Single-atom Cu promotes the electrochemical reduction of nitrate in water to high value-added ammonia. [Display omitted]