Engineering the Co(II)/Co(III) Redox Cycle and Coδ+ Species Shuttle for Nitrate-to-Ammonia Conversion

Yongguang Bu; Wenjing Yu; Wenkai Zhang; Chao Wang; Jie Ding; Guandao Gao

doi:10.1021/acs.nanolett.3c04920

Engineering the Co(II)/Co(III) Redox Cycle and Co^δ+ Species Shuttle for Nitrate-to-Ammonia Conversion

Nano Lett. 2024 Mar 6;24(9):2812-2820. doi: 10.1021/acs.nanolett.3c04920. Epub 2024 Feb 24.

Authors

Yongguang Bu¹, Wenjing Yu², Wenkai Zhang¹, Chao Wang³, Jie Ding^{1

4}, Guandao Gao^{1

5}

Affiliations

¹ State Key Laboratory of Pollution Control and Resource Reuse, School of Environment, Nanjing University, Nanjing 210023, China.
² Research Center of Environmental Science and Engineering, School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
³ School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002, China.
⁴ Shenzhen Research Institute of Nanjing University, Shenzhen 518057, China.
⁵ Chongqing Innovation Research Institute of Nanjing University, Chongqing 401121, China.

PMID: 38396345
DOI: 10.1021/acs.nanolett.3c04920

Abstract

Electroreduction of waste nitrate to valuable ammonia offers a green solution for environmental restoration and energy storage. However, the electrochemical self-reconstruction of catalysts remains a huge challenge in terms of maintaining their stability, achieving the desired active sites, and managing metal leaching. Herein, we present an electrical pulse-driven Co surface reconstruction-coupled Co^δ+ shuttle strategy for the precise in situ regulation of the Co(II)/Co(III) redox cycle on the Co-based working electrode and guiding the dissolution and redeposition of Co-based particles on the counter electrode. As result, the ammonia synthesis performance and stability are significantly promoted while cathodic hydrogen evolution and anodic ammonia oxidation in a membrane-free configuration are effectively blocked. A high rate of ammonia production of 1.4 ± 0.03 mmol cm^-2 h^-1 is achieved at -0.8 V in a pulsed system, and the corresponding nitrate-to-ammonia Faraday efficiency is 91.7 ± 1.0%. This work holds promise for the regulation of catalyst reactivity and selectivity by engineering in situ controllable structural and chemical transformations.

Keywords: Co(II)/Co(III) redox cycle; Co-based catalysts; Coδ+ species shuttle; in situ pulsed electrolysis; nitrate-to-ammonia conversion; reversible surface reconstruction.