Metal-organic framework derived carbon-supported bimetallic copper-nickel alloy electrocatalysts for highly selective nitrate reduction to ammonia

Yong Liu; Bangwei Deng; Kanglu Li; Hong Wang; Yanjuan Sun; Fan Dong

doi:10.1016/j.jcis.2022.01.127

Metal-organic framework derived carbon-supported bimetallic copper-nickel alloy electrocatalysts for highly selective nitrate reduction to ammonia

J Colloid Interface Sci. 2022 May 15:614:405-414. doi: 10.1016/j.jcis.2022.01.127. Epub 2022 Jan 25.

Authors

Yong Liu¹, Bangwei Deng², Kanglu Li³, Hong Wang², Yanjuan Sun⁴, Fan Dong⁵

Affiliations

¹ Research Center for Environmental and Energy Catalysis, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China.
² Research Center for Environmental and Energy Catalysis, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China; Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313000, China.
³ Research Center for Environmental and Energy Catalysis, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China; College of Architecture and Environment, Sichuan University, Chengdu, Sichuan 610065, China.
⁴ Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313000, China; School of Resources and Environment, University of Electronic Science and Technology of China, Chengdu 611731, China.
⁵ Research Center for Environmental and Energy Catalysis, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China; Yangtze Delta Region Institute (Huzhou), University of Electronic Science and Technology of China, Huzhou 313000, China. Electronic address: dongfan@uestc.edu.cn.

PMID: 35108632
DOI: 10.1016/j.jcis.2022.01.127

Abstract

Developing electrocatalysts for efficient reduction of nitrate contaminant to value-added ammonia as energy carrier is a pivotal part for restoring the nitrogen cycle. However, the selectivity of ammonia is far from satisfaction, often suffering from accumulation of toxic nitrite byproduct. Herein, a series of CuNi alloy nanoparticles embedded in nitrogen-doped carbon matrix (CuNi/NC) with hierarchical pores were fabricated by pyrolysis of bimetallic metal-organic frameworks (MOFs). The catalysts exhibited excellent selectivity (94.4%) and faradaic efficiency (79.6%) for nitrate reduction to ammonia, greatly outperforming the performance of monometallic Cu/NC (selectivity of 60.8% and faradaic efficiency of 60.6%). Impressively, the introduction of nickel distinctly suppressed the production of toxic byproduct of nitrite. Online differential electrochemical mass spectrometry (DEMS) and in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) tests were utilized to reveal the key intermediates and the reaction pathway. Density functional theory (DFT) calculations demonstrated that the introducing of nickel into copper lattice modified both the electronic and geometric structures of the catalysts. The copper and nickel sites in the CuNi alloy catalysts operate synergistically to facilitate the hydrogenation of NO₂* to HNO₂* and suppress the hydrogen evolution reaction, boosting the selective formation of ammonia. This work could provide a new synthetic route for bimetallic catalysts and mechanistic understanding for nitrate to ammonia reaction.

Keywords: Ammonia production; Electrocatalyst; Nitrate reduction; Reaction pathway; Selectivity.