Cu-Fe crystalline/amorphous interface enables efficient electrocatalytic nitrate-to-ammonia conversion
image: An amorphous/crystalline Fe-Cu catalyst was prepared via ultrasonic-assisted reduction. The amorphous/crystalline interface promoted active hydrogen species generation and electron transfer through enhanced water activation and electronic modulation.
Credit: Nano research, Tsinghua University Press
A recent study by Hai-tao Li and colleagues at Jiangsu University developed an amorphous/crystalline dual-phase Fe/Cu (a-Fe/Cu) catalyst via an ultrasonic method, demonstrating exceptional activity toward electrocatalytic nitrate reduction to ammonia. The synthetic strategy employed in the production of the a-Fe/Cu catalyst is detailed, and the impact of its unique interfacial structure in promoting active hydrogen is discussed. The research goes on to highlight the superior performance of this catalyst, achieving a high ammonia yield rate of 4.67 mol g⁻¹ h⁻¹ with a Faradaic efficiency of up to 93.48% at -0.5 V vs. RHE. Finally, the practical applicability of the catalyst is demonstrated through its integration into a Zn-NO3– battery, showcasing its potential in energy conversion and storage technologies.
“In this work, we present the fabrication of an amorphous/crystalline dual-phase Fe/Cu catalyst using an ultrasonic method, which exhibits outstanding performance for electrocatalytic nitrate reduction to ammonia. The influence of the amorphous Fe phase on promoting water dissociation and generating active hydrogen species is comprehensively described. The synergistic interaction between crystalline Cu and amorphous Fe optimizes the electronic structure, enhancing nitrate adsorption and facilitating efficient electron transfer. We also demonstrate the successful assembly of a Zn-NO₃⁻ battery using our catalyst, achieving a peak power density of 2.91 mW cm⁻².” said Haitao Li, senior author of the paper and professor at the Energy Research Institute of Jiangsu University.
Electrocatalytic nitrate reduction reaction holds significant promise for sustainable ammonia synthesis and wastewater treatment. However, the process involves a complex multi-electron/proton transfer and suffers from competing side reactions, making high ammonia selectivity challenging. Precious metal catalysts are efficient but costly, whereas Fe-based catalysts, though cost-effective, often face issues like particle aggregation and slow kinetics.
The team outlined the synthesis and characterization of the a-Fe/Cu catalyst. “The a-Fe/Cu catalyst, synthesized via ultrasonic-assisted reduction, possesses a unique amorphous/crystalline interface. This interface promotes active hydrogen species generation and electron transfer through enhanced water activation and electronic modulation,” said Haitao Li. Scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) confirmed the distinct granular morphology and the coexistence of amorphous and crystalline phases. X-ray photoelectron spectroscopy (XPS) analysis indicated electron transfer from Cu to Fe at the interface, optimizing the electronic structure.
The positive surface charge and the disordered atomic arrangement in the amorphous Fe phase greatly influence the catalyst's reactivity by providing numerous active sites. These characteristics enable the a-Fe/Cu catalyst to be utilized efficiently in nitrate reduction.
Haitao Li said, “The catalytic activity is based on the specific interface which facilitates water dissociation. In-situ analyses demonstrated that the amorphous Fe phase enhances the dynamic equilibrium between the production of active hydrogen and its consumption by nitrogen intermediates, leading to high selectivity for ammonia production.”
This research team offers insights into the reaction mechanism through in-situ spectroscopic studies. “In-situ Raman and infrared spectroscopy confirmed the progressive consumption of nitrate and the formation of key intermediates like hydroxylamine (NH₂OH) and ammonium (NH₄⁺), elucidating the reaction pathway,” said Haitao Li.
The catalyst also demonstrated excellent stability during continuous operation, maintaining high performance over seven cycles. Furthermore, the assembled Zn-NO3– battery delivered a peak power density of 2.91 mW cm⁻² and an ammonia Faradaic efficiency of 81.66% at 30 mA cm–2, highlighting its dual functionality for energy storage and ammonia production.
Other contributors include Xinya Yuan, Yaxi Li, Yuanyaun Cheng, Naiyun Liu, Yunliang Liu, Sobia Jabeen from the Institute for Energy Research of Jiangsu University; and Bing Tang from the department of Chemistry of Tsinghua University.
This research was funded by the National Natural Science Foundation of China (Grants 52072152, 51802126), the Jiangsu University Jinshan Professor Fund, the Jiangsu Specially-Appointed Pro-fessor Fund, the Open Fund from Guangxi Key Laboratory of Electrochemical Energy Materials, Zhenjiang “Jinshan Talents” Project 2021, China PostDoctoral Science Foundation (2022M721372 and 2024M761711), the “Doctor of Entrepreneurship and Innovation” in Jiangsu Province (JSSCBS20221197), the Natural Science Foundation for Colleges and Universities in Jiangsu Province (No. 24KJB480003), the Postdoctoral Fellowship Program and China Postdoctoral Science Foundation (BX20250269) and the Postgraduate Research and Practice Innovation Program of Jiangsu Province (Nos. KYCX22_3645 and KYCX24_3964).
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Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.