Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst

Zhen-Yu Wu; Mohammadreza Karamad; Xue Yong; Qizheng Huang; David A Cullen; Peng Zhu; Chuan Xia; Qunfeng Xiao; Mohsen Shakouri; Feng-Yang Chen; Jung Yoon Timothy Kim; Yang Xia; Kimberly Heck; Yongfeng Hu; Michael S Wong; Qilin Li; Ian Gates; Samira Siahrostami; Haotian Wang

doi:10.1038/s41467-021-23115-x

Electrochemical ammonia synthesis via nitrate reduction on Fe single atom catalyst

Nat Commun. 2021 May 17;12(1):2870. doi: 10.1038/s41467-021-23115-x.

Authors

Zhen-Yu Wu¹, Mohammadreza Karamad², Xue Yong³, Qizheng Huang¹, David A Cullen⁴, Peng Zhu¹, Chuan Xia¹, Qunfeng Xiao⁵, Mohsen Shakouri⁵, Feng-Yang Chen¹, Jung Yoon Timothy Kim¹, Yang Xia¹, Kimberly Heck¹, Yongfeng Hu⁵, Michael S Wong¹, Qilin Li⁶, Ian Gates², Samira Siahrostami⁷, Haotian Wang^{8

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Affiliations

¹ Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, USA.
² Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB, Canada.
³ Department of Chemistry, University of Calgary, Calgary, AB, Canada.
⁴ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
⁵ Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK, Canada.
⁶ Department of Civil and Environmental Engineering, Rice University, Houston, TX, USA.
⁷ Department of Chemistry, University of Calgary, Calgary, AB, Canada. samira.siahrostami@ucalgary.ca.
⁸ Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, USA. htwang@rice.edu.
⁹ Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA. htwang@rice.edu.
¹⁰ Department of Chemistry, Rice University, Houston, TX, USA. htwang@rice.edu.
¹¹ Azrieli Global Scholar, Canadian Institute for Advanced Research (CIFAR), Toronto, ON, Canada. htwang@rice.edu.

Abstract

Electrochemically converting nitrate, a widespread water pollutant, back to valuable ammonia is a green and delocalized route for ammonia synthesis, and can be an appealing and supplementary alternative to the Haber-Bosch process. However, as there are other nitrate reduction pathways present, selectively guiding the reaction pathway towards ammonia is currently challenged by the lack of efficient catalysts. Here we report a selective and active nitrate reduction to ammonia on Fe single atom catalyst, with a maximal ammonia Faradaic efficiency of ~ 75% and a yield rate of up to ~ 20,000 μg h^-1 mg_cat.^-1 (0.46 mmol h^-1 cm^-2). Our Fe single atom catalyst can effectively prevent the N-N coupling step required for N₂ due to the lack of neighboring metal sites, promoting ammonia product selectivity. Density functional theory calculations reveal the reaction mechanisms and the potential limiting steps for nitrate reduction on atomically dispersed Fe sites.