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Synthesis and Characterization of Binary Nanocomposites Based on Non-Precious Transition Metals for the Electrochemical Reduction of Nitrate to Ammonia

Lotf Zaree, Reza | 2025

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58470 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Taherinia, Davood
  7. Abstract:
  8. Nitrate contamination of water resources is a major environmental concern with adverse impacts on human health and ecosystem stability. In this study, the electrochemical reduction of nitrate to ammonia was investigated as a green approach for removing nitrate from polluted waters while simultaneously producing ammonia as a valuable industrial product. In the first stage, pure nickel cobaltite and its doped variants with different metals were synthesized via hydrothermal and calcination methods. The crystal structure, morphology, atomic molar ratios, and empirical formulas were characterized using XRD and SEM/EDS techniques. Electrochemical measurements, including linear sweep voltammetry, electrochemical impedance spectroscopy, and chronoamperometry, revealed that under neutral conditions with a PBS buffer, Cu doped nickel cobaltite exhibited the best electrocatalytic performance among the investigated dopants, achieving a current density of –70 mA·cm⁻² and selectivity and Faradaic efficiency of 68.4% and 61.2%, respectively, at –0.9 V. In the second stage, a 〖"NiCo" 〗_"2" "O" _"4" "@CoCu LDH" composite was synthesized using the nickel cobaltite from the first stage via a hydrothermal method. XRD and SEM/EDS analyses confirmed its crystalline structure and favorable morphology. Compared to its individual components—nickel cobaltite and CoCu layered double hydroxide—the composite showed remarkable improvement in electrochemical performance. In neutral PBS buffer, it achieved a current density of –110 mA·cm⁻² and selectivity and Faradaic efficiency values of 72.1% and 63.2%, respectively, at –0.9 V, thus being identified as an optimized, high performance electrocatalyst. Further investigation of composites with different molar ratios of spinel to layered double hydroxide revealed that the composition with a 1:20 molar ratio exhibited the best performance
  9. Keywords:
  10. Electrocatalysts ; Non-Precious Metals ; Spinel ; Layered Double Hydroxide (LDH) ; Electrochemical Nitrate Reduction to Ammonia ; Transition Metals ; Binary Compounds

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