Balanced NOx- and Proton Adsorption for Efficient Electrocatalytic NOx- to NH3 Conversion

Yue Hu; Jiawei Liu; Carmen Lee; Wenyu Luo; Jinfeng Dong; Zhishan Liang; Mengxin Chen; Erhai Hu; Mingsheng Zhang; Xiang Yun Debbie Soo; Qiang Zhu; Fengkun Li; Rajdeep Singh Rawat; Man-Fai Ng; Lixiang Zhong; Bo Han; Dongsheng Geng; Qingyu Yan

doi:10.1021/acsnano.3c06798

Balanced NO_x^- and Proton Adsorption for Efficient Electrocatalytic NO_x^- to NH₃ Conversion

ACS Nano. 2023 Dec 12;17(23):23637-23648. doi: 10.1021/acsnano.3c06798. Epub 2023 Nov 18.

Authors

Yue Hu^{1

2}, Jiawei Liu³, Carmen Lee², Wenyu Luo², Jinfeng Dong², Zhishan Liang², Mengxin Chen², Erhai Hu², Mingsheng Zhang³, Xiang Yun Debbie Soo³, Qiang Zhu³, Fengkun Li^{4

5}, Rajdeep Singh Rawat⁴, Man-Fai Ng⁶, Lixiang Zhong⁷, Bo Han⁸, Dongsheng Geng^{1

9}, Qingyu Yan^{2

3}

Affiliations

¹ School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China.
² School of Materials Science and Engineering, Nanyang Technological University, 639798, Singapore.
³ Institute of Materials Research and Engineering, A*STAR, 138634, Singapore.
⁴ Natural Science and Science Education, National Institute of Education, Nanyang Technological University, 637616, Singapore.
⁵ College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, Jiangsu, China.
⁶ Institute of High Performance Computing (IHPC), A*STAR, 138632, Singapore.
⁷ School of Physics, Beijing Institute of Technology, Beijing 100081, China.
⁸ SCARCE Laboratory, Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, 637459, Singapore.
⁹ School of Chemistry and Materials Science, Nanjing University of Information Science & Technology, Nanjing 210044, China.

PMID: 37979042
DOI: 10.1021/acsnano.3c06798

Abstract

Electrocatalytic nitrate (NO₃^-)/nitrite (NO₂^-) reduction reaction (eNO_x^-RR) to ammonia under ambient conditions presents a green and promising alternative to the Haber-Bosch process. Practically available NO_x^- sources, such as wastewater or plasma-enabled nitrogen oxidation reaction (p-NOR), typically have low NO_x^- concentrations. Hence, electrocatalyst engineering is important for practical eNO_x^-RR to obtain both high NH₃ Faradaic efficiency (FE) and high yield rate. Herein, we designed balanced NO_x^- and proton adsorption by properly introducing Cu sites into the Fe/Fe₂O₃ electrocatalyst. During the eNO_x^-RR process, the H adsorption is balanced, and the good NO_x^- affinity is maintained. As a consequence, the designed Cu-Fe/Fe₂O₃ catalyst exhibits promising performance, with an average NH₃ FE of ∼98% and an average NH₃ yield rate of 15.66 mg h^-1 cm^-2 under the low NO₃^- concentration (32.3 mM) of typical industrial wastewater at an applied potential of -0.6 V versus reversible hydrogen electrode (RHE). With low-power direct current p-NOR generated NO_x^- (23.5 mM) in KOH electrolyte, the Cu-Fe/Fe₂O₃ catalyst achieves an FE of ∼99% and a yield rate of 15.1 mg h^-1 cm^-2 for NH₃ production at -0.5 V (vs RHE). The performance achieved in this study exceeds industrialization targets for NH₃ production by exploiting two available low-concentration NO_x^- sources.

Keywords: ammonia production; balanced NOx− and proton adsorption; electrocatalytic nitrate/nitrite reduction; industrial wastewater; plasma-enabled nitrogen oxidation.