Electrocatalytic Nitrate Reduction on Oxide-Derived Silver with Tunable Selectivity to Nitrite and Ammonia

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Liu, Hengzhou
Park, Jaeryul
Chen, Yifu
Qiu, Yang
Cheng, Yan
Srivastava, Kartik
Gu, Shuang
Roling, Luke
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Shanks, Brent
Distinguished Professor
Li, Wenzhen
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NSF Engineering Research Center for Biorenewable Chemicals
Founded in 2008 with more than $44M in federal, industry, and Iowa State University funding, CBiRC works in tandem with Iowa and the nation’s growing biosciences sector. CBiRC’s goal is to lead the transformation of the chemical industry toward a future where chemicals derived from biomass resources will lead to the production of new bioproducts to meet evolving societal needs.
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Chemical and Biological Engineering

The function of the Department of Chemical and Biological Engineering has been to prepare students for the study and application of chemistry in industry. This focus has included preparation for employment in various industries as well as the development, design, and operation of equipment and processes within industry.Through the CBE Department, Iowa State University is nationally recognized for its initiatives in bioinformatics, biomaterials, bioproducts, metabolic/tissue engineering, multiphase computational fluid dynamics, advanced polymeric materials and nanostructured materials.

The Department of Chemical Engineering was founded in 1913 under the Department of Physics and Illuminating Engineering. From 1915 to 1931 it was jointly administered by the Divisions of Industrial Science and Engineering, and from 1931 onward it has been under the Division/College of Engineering. In 1928 it merged with Mining Engineering, and from 1973–1979 it merged with Nuclear Engineering. It became Chemical and Biological Engineering in 2005.

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1913 - present

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  • Department of Chemical Engineering (1913–1928)
  • Department of Chemical and Mining Engineering (1928–1957)
  • Department of Chemical Engineering (1957–1973, 1979–2005)
    • Department of Chemical and Biological Engineering (2005–present)

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Removing excess nitrate (NO3–) from waste streams has become a significant environmental and health topic. However, realizing highly selective NO3– conversion toward N2, primarily via electrocatalytic conversions, has proven challenging, largely because of the kinetically uncontrollable NO3–-to-NO2– pathway and unfavorable N–N coupling. Herein, we discovered unique and ultra-high electrocatalytic NO3–-to-NO2–activity on oxide-derived silver (OD-Ag). Up to 98% selectivity and 95% Faradaic efficiency (FE) of NO2– were observed and maintained under a wide potential window. Benefiting from the superior NO3–-to-NO2–activity, further reduction of accumulated NO2– to NH4+ was well regulated by the cathodic potential and achieved an NH4+ FE of 89%, indicating a tunable selectivity to the key nitrate reduction products (NO2– or NH4+) on OD-Ag. Density functional theory computations provided insights into the unique NO2– selectivity on Ag electrodes compared with Cu, showing the critical role of a proton-assisted mechanism. Based on the ultra-high NO3–-to-NO2– activity on OD-Ag, we designed a novel electrocatalytic–catalytic combined process for denitrifying real-world NO3–-containing agricultural wastewater, leading to 95+% of NO3– conversion to N2 with minimal NOX gases. In addition to the wastewater treatment process to N2 and the electrochemical synthesis of NH3, NO2– derived from electrocatalytic NO3– conversion can serve as a reactive platform for the distributed production of various nitrogen products.


This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in ACS Catalysis, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/acscatal.1c01525. Posted with permission.

Fri Jan 01 00:00:00 UTC 2021