Development of new electrocatalysts for the electrochemical reduction of nitrogen to ammonia

• Autores: Roumayssa Amrine
• Directores de la Tesis: José Solla Gullón (dir. tes.)
• Lectura: En la Universitat d'Alacant / Universidad de Alicante ( España ) en 2025
• Idioma: español
• Tribunal Calificador de la Tesis: Edelmira Valero Ruiz (presid.), Rosa M. Arán Ais (secret.), Jonathan Albo Sánchez (voc.)
• Programa de doctorado: Programa de Doctorado en Electroquímica. Ciencia y Tecnología por la Universidad Autónoma de Barcelona; la Universidad Autónoma de Madrid; la Universidad de Alicante; la Universidad de Barcelona; la Universidad de Burgos; la Universidad de Córdoba; la Universidad de Lleida; la Universidad de Murcia; la Universidad de Sevilla; la Universidad Politécnica de Cartagena y la Universitat de València (Estudi General)
• Materias:
  • Física
    • Química física
      • Electroquímica
  • Química
    • Química inorgánica
      • Compuestos de nitrógeno
• Enlaces
  • Tesis en acceso abierto en: RUA
• Resumen

  • This doctoral thesis is focused on the development and characterization of new electrocatalysts based on different types of materials for their application in the electrochemical nitrogen reduction reaction (NRR). This reaction is proposed as a sustainable alternative to the Haber–Bosch process for ammonia synthesis, as it allows ammonia production under mild operating conditions. However, challenges related to selectivity, reproducibility, and contamination problems require a rigorous experimental approach. Various electrocatalysts were designed and evaluated, including nanoparticles of noble metals (Pt, Rh) and post-transition metals (Bi, Sn), as well as bimetallic Pt-Rh and Bi-Sn alloys. In addition, electrocatalysts based on metal-organic frameworks (MOFs), both metalated (Ni, Co, Cu, Fe) and non-metalated, were studied, along with Fe-N-C-type materials and other metallic combinations. The objective was to investigate how the type of material, catalyst composition, electrode loading, electrolyte selection, and other experimental parameters influence NRR activity. Among the results obtained, the Pt₇₀Rh₃₀/C catalyst exhibited the highest Faradaic efficiency (~23%) and good stability, particularly when a low electrode loading (0.4 mg.cm⁻²) was used, which enhanced reactant diffusion and exposure of active sites. In contrast, Bi and Sn nanoparticles showed no significant activity under the tested conditions. Ni-based MOFs, particularly PCN-224-Ni, offered a favorable combination of activity and stability, which was further improved by the incorporation of fluorine without compromising catalytic performance. A rigorous experimental protocol was established to ensure the reliability of the results, including blank experiments, analysis of contaminants (NO₃⁻, NO₂⁻), and precise NH₃ quantification via spectrophotometric methods. This approach enabled clear differentiation between true catalytic activity and experimental false positives. Overall, this thesis contributes not only to the design of promising new materials for NRR but also to the development of a standardized and reproducible methodology that supports meaningful progress in the field of sustainable electrochemical ammonia production.