Reaction intermediate-mediated electrocatalyst synthesis favors specified facet and defect exposure for efficient nitrate-ammonia conversion

• Published in: Energy & environmental science Vol. 14; no. 9; pp. 4989 - 4997
• Main Authors: Hu, Qi, Qin, Yongjie, Wang, Xiaodeng, Wang, Ziyu, Huang, Xiaowan, Zheng, Hongju, Gao, Keru, Yang, Hengpan, Zhang, Peixin, Shao, Minhua, He, Chuanxin
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 15.09.2021
• Subjects: Ammonia; Chemical reduction; Chemical synthesis; Copper; Electrocatalysts; Electrochemistry; Exposure; Haber Bosch process; Hydrogen evolution reactions; Intermediates; Nitrogen; Performance enhancement; Reaction intermediates; Robustness; Surface defects
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/d1ee01731d

The electrochemical nitrate (NO 3 − ) reduction reaction (NO 3 − RR), with much faster kinetics than the nitrogen (N 2 ) reduction, provides new opportunities to harvest ammonia (NH 3 ) under ambient conditions. However, the NH 3 production rate of NO 3 − RR is still much inferior to that of the industrial Haber-Bosch route due to the lack of robust electrocatalysts for suppressing the hydrogen evolution reaction (HER) at large current densities. Herein, we demonstrate an electrocatalyst synthesis strategy based on the in situ electrochemical reduction of ultrathin copper-oxide nanobelts under NO 3 − RR conditions, which favorably exposes Cu(100) facets and abundant surface defects, thereby markedly facilitating the NO 3 − RR yet hindering the HER. We discover that the intermediates of NO 3 − RR ( i.e. , N*) can serve as capping agents for controlling the exposed facets during the reduction. Impressively, in alkaline media, the NO 3 − RR catalyzed by defective Cu(100) facets gives a NH 3 yield rate which is 2.3-fold higher than that of the Haber-Bosch process. The synergy of Cu(100) facets and defects, which upshifts the d band center of Cu, is the key to excellent performance. The reaction intermediate-mediated strategy demonstrated in this study offers a fresh concept and robust methodology for directional electrocatalyst synthesis to achieve markedly enhanced performance. An intermediate-mediated approach was proposed to synthesize copper, rich in (100) facets and defects, for highly efficient nitrate reduction.