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Communication Dans Un Congrès Année : 2022

Bimetallic earth-abundant electrocatalysts pave the way for sustainable N-recovery from nitrate polluted wastewater

Résumé

Nitrate (NO3-) is a common pollutant present in ground and surface water due to the use fertilizers [1]. High nitrate concentrations in water may pose a potential risk for human health since induces blue baby syndrome and may trigger cancer. Therefore, the Environmental Protection Agency (EPA) established a maximum concentration level of 10 mg L-1 as N [2]. Traditional treatment for nitrate includes reverse osmosis and biological treatment. However, these techniques produce concentrated brines and have a high physical footprint that limits their wide implementation. Electrochemical reduction of nitrate (ERN) is emerging as treatment alternative. The ERN can reduce NO3- toward N2 gas for drinking water treatment, or towards NH3 as added-value product [3]. The selectivity of this reduction reaction depends on the electrocatalysts surface and the preferential mechanism that may involve either/both direct charge transfer or/and hydrogenation. Surface characteristics and composition may modify the adsorption energy of intermediates and the relation NO*/H* that define the reaction selectivity. Platinum group materials (i.e., Pd, Pt, Ru, Rh) present a high selectivity to N2 for drinking water treatment. However, these materials are considered limited resources and pricey. Meanwhile, earth-abundant materials (i.e., Cu, Ni, Fe, Sn) may appear as cheaper alternative despite their lower performance [4]. Generating bimetallic structures at the nanoscale can enhance ERN and tune product selectivity while decreasing reliance on platinum group metals as electrocatalysts. In this study, three-dimensional bimetallic electrodes using earth-abundant materials were prepared by controlled electrodeposition over Cu foam. Structural and morphological characterization was studied by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope. Nitrate reduction evaluation of realistic concentration (30 mg L-1 as N) were tested for Cu-Co, Cu-Ni, and Cu-Cu electrodes under different current densities 5, 10, 20, 40 and 80 mA cm-2. Bimetallic structures dramatically increased electrocatalytic responses respect to pristine copper substrate and surpassed that of conventional Pt electrodes. Nitrate removal, selectivity, Faradaic efficiency, and electrical energy per order were calculated for each electrode at different current densities. Results showed an outstanding nitrate conversion and selectivity for the Cu-Co nanocomposite electrode that attained complete abatement in less than 2h of electrolysis with ca. 90% selectivity towards ammonia. These results provide a framework for earth-abundant materials in electrocatalytic nitrate reduction and scope of selectivity for bimetallic electrodes. References [1]S. Singh, A.G. Anil, V. Kumar, D. Kapoor, S. Subramanian, J. Singh, P.C. Ramamurthy, Nitrates in the environment: A critical review of their distribution, sensing techniques, ecological effects and remediation, Chemosphere. 287 (2022) 131996. https://doi.org/10.1016/j.chemosphere.2021.131996. [2]Y.G. Teng, R. Zuo, Y. Xiong, J. Wu, Y.Z. Zhai, J. Su, Risk assessment framework for nitrate contamination in groundwater for regional management, Sci. Total Environ. 697 (2019) 134102. https://doi.org/10.1016/j.scitotenv.2019.134102. [3]A.S. Fajardo, P. Westerhoff, C.M. Sanchez-Sanchez, S. Garcia-Segura, Earth-abundant elements a sustainable solution for electrocatalytic reduction of nitrate, Appl. Catal. B Environ. 281 (2021) 119465. https://doi.org/10.1016/j.apcatb.2020.119465. [4]S. Garcia-Segura, M. Lanzarini-Lopes, K. Hristovski, P. Westerhoff, Electrocatalytic reduction of nitrate: Fundamentals to full-scale water treatment applications, Appl. Catal. B Environ. 236 (2018) 546–568. https://doi.org/10.1016/j.apcatb.2018.05.041.

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hal-03800566 , version 1 (06-10-2022)

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  • HAL Id : hal-03800566 , version 1

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Gabriel Antonio Cerrón-Calle, Diana Leon, Ana S Fajardo, Carlos M Sánchez-Sánchez, Sergi Garcia-Segura. Bimetallic earth-abundant electrocatalysts pave the way for sustainable N-recovery from nitrate polluted wastewater. 73 rd Annual Meeting online of the International Society of Electrochemistry (ISE 2022), Katharina Krischer and Andrea Russell, Sep 2022, Lausanne (siège de l'ISE), Switzerland. ⟨hal-03800566⟩
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