{"title":"Reversed I<sub>1</sub>Cu<sub>4</sub> single-atom sites for superior neutral ammonia electrosynthesis with nitrate.","authors":"Bing Zhou, Yawen Tong, Yancai Yao, Weixing Zhang, Guangming Zhan, Qian Zheng, Wei Hou, Xiang-Kui Gu, Lizhi Zhang","doi":"10.1073/pnas.2405236121","DOIUrl":null,"url":null,"abstract":"<p><p>Electrochemical ammonia (NH<sub>3</sub>) synthesis from nitrate reduction (NITRR) offers an appealing solution for addressing environmental concerns and the energy crisis. However, most of the developed electrocatalysts reduce NO<sub>3</sub><sup>-</sup> to NH<sub>3</sub> via a hydrogen (H*)-mediated reduction mechanism, which suffers from undesired H*-H* dimerization to H<sub>2</sub>, resulting in unsatisfactory NH<sub>3</sub> yields. Herein, we demonstrate that reversed I<sub>1</sub>Cu<sub>4</sub> single-atom sites, prepared by anchoring iodine single atoms on the Cu surface, realized superior NITRR with a superior ammonia yield rate of 4.36 mg h<sup>-1</sup> cm<sup>-2</sup> and a Faradaic efficiency of 98.5% under neutral conditions via a proton-coupled electron transfer (PCET) mechanism, far beyond those of traditional Cu sites (NH<sub>3</sub> yield rate of 0.082 mg h<sup>-1</sup> cm<sup>-2</sup> and Faradaic efficiency of 36.5%) and most of H*-mediated NITRR electrocatalysts. Theoretical calculations revealed that I single atoms can regulate the local electronic structures of adjacent Cu sites in favor of stronger O-end-bidentate NO<sub>3</sub><sup>-</sup> adsorption with dual electron transfer channels and suppress the H* formation from the H<sub>2</sub>O dissociation, thus switching the NITRR mechanism from H*-mediated reduction to PCET. By integrating the monolithic I<sub>1</sub>Cu<sub>4</sub> single-atom electrode into a flow-through device for continuous NITRR and in situ ammonia recovery, an industrial-level current density of 1 A cm<sup>-2</sup> was achieved along with a NH<sub>3</sub> yield rate of 69.4 mg h<sup>-1</sup> cm<sup>-2</sup>. This study offers reversed single-atom sites for electrochemical ammonia synthesis with nitrate wastewater and sheds light on the importance of switching catalytic mechanisms in improving the performance of electrochemical reactions.</p>","PeriodicalId":20548,"journal":{"name":"Proceedings of the National Academy of Sciences of the United States of America","volume":null,"pages":null},"PeriodicalIF":9.4000,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Proceedings of the National Academy of Sciences of the United States of America","FirstCategoryId":"103","ListUrlMain":"https://doi.org/10.1073/pnas.2405236121","RegionNum":1,"RegionCategory":"综合性期刊","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2024/9/3 0:00:00","PubModel":"Epub","JCR":"Q1","JCRName":"MULTIDISCIPLINARY SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Electrochemical ammonia (NH3) synthesis from nitrate reduction (NITRR) offers an appealing solution for addressing environmental concerns and the energy crisis. However, most of the developed electrocatalysts reduce NO3- to NH3 via a hydrogen (H*)-mediated reduction mechanism, which suffers from undesired H*-H* dimerization to H2, resulting in unsatisfactory NH3 yields. Herein, we demonstrate that reversed I1Cu4 single-atom sites, prepared by anchoring iodine single atoms on the Cu surface, realized superior NITRR with a superior ammonia yield rate of 4.36 mg h-1 cm-2 and a Faradaic efficiency of 98.5% under neutral conditions via a proton-coupled electron transfer (PCET) mechanism, far beyond those of traditional Cu sites (NH3 yield rate of 0.082 mg h-1 cm-2 and Faradaic efficiency of 36.5%) and most of H*-mediated NITRR electrocatalysts. Theoretical calculations revealed that I single atoms can regulate the local electronic structures of adjacent Cu sites in favor of stronger O-end-bidentate NO3- adsorption with dual electron transfer channels and suppress the H* formation from the H2O dissociation, thus switching the NITRR mechanism from H*-mediated reduction to PCET. By integrating the monolithic I1Cu4 single-atom electrode into a flow-through device for continuous NITRR and in situ ammonia recovery, an industrial-level current density of 1 A cm-2 was achieved along with a NH3 yield rate of 69.4 mg h-1 cm-2. This study offers reversed single-atom sites for electrochemical ammonia synthesis with nitrate wastewater and sheds light on the importance of switching catalytic mechanisms in improving the performance of electrochemical reactions.
期刊介绍:
The Proceedings of the National Academy of Sciences (PNAS), a peer-reviewed journal of the National Academy of Sciences (NAS), serves as an authoritative source for high-impact, original research across the biological, physical, and social sciences. With a global scope, the journal welcomes submissions from researchers worldwide, making it an inclusive platform for advancing scientific knowledge.