Generation of Ammonia by High Concentrated Nitrate Electrolyte Electroreduction
Marcelo Chavez a, Sebastian Murcia a, Joan Ramon Morante a
a Catalonia Institute for Energy Research−IREC, Jardins de les Dones de Negre 1, 2ª pl., Sant Adrià de Besòs, Spain
Proceedings of International Conference on Frontiers in Electrocatalytic Transformations (INTERECT)
València, Spain, 2021 November 22nd - 23rd
Organizers: Elena Mas Marzá and Ward van der Stam
Contributed talk, Marcelo Chavez, presentation 020
Publication date: 10th November 2021

Along with mechanical, electrical, and thermal energy storage systems, chemical approaches have recently captured more attention of many sectors, giving some unique advantages. Among the most important, the flexibility of storing large quantities of energy over long periods at any location and lower costs per unity of stored energy is worth mentioning. Many chemical compounds, synthesized with renewable energy, are capable candidates to serve as chemical storage systems such as alcohols, hydrocarbons, and ammonia. In the case of ammonia, its versatile applications, either for power or as a chemical precursor, have put it at the center of an intensive attempt to develop technologies to replace its traditional forms of production (The Haber-Bosh process).

Upgrading nitrogen oxyanions to high-value nitrogen-based products is one promising approach for fuel, energy chemical storage, and chemical commodities production. Among several monometallic and bimetallic catalysts, copper and titanium have attracted attention because of their high ability to convert nitrate or nitrite into ammonia with an appreciable efficiency. Although numerous efforts have been made to achieve a combination of high nitrate conversion with a high partial current efficiency and selectivity to ammonia, it remains a challenge to obtain a high-quality bimetallic catalyst for the electroreduction of NO3- / NO2- that can reach all the mentioned efficiency parameters simultaneously. In this work, we analyze the performance in direct electroreduction of a high nitrate concentrated electrolyte of two different cathode materials (Cu Foil, Ti Foil) and the effects on the efficiency parameters of combining these materials in a bimetallic catalyst (Cu Nanoparticles / Ti Foil). In a 0.4 M KNO3 electrolyte, the bimetallic electrocatalyst (CuNP deposited on Ti Foil) exhibits a better global efficiency in ammonia yield than the monometallic electrodes. The CuNP/Ti Foil electrocatalyst showed a Faradaic efficiency (FE) of 80% with a Selectivity (SE) of 54% and a total nitrate conversion of 17% at -750 mV vs. Reversible Hydrogen Electrode (RHE). Separately the monometallic electrodes showed high FE and SE to ammonia in the case of the Ti Foil (92%, 57%, respectively) and a high nitrate conversion capacity in the case of the Cu Foil (27%) at more negative potentials. The combination of all efficiency parameters suggests the synergistic effect of combining Cu and Ti in a promising bimetallic electrode for nitrate electroreduction to ammonia.

This work is supported by Ministerio de Ciencia e Innovación under CERES project (PID2020-116093RB-C42) and FPI grant (PRE2018-083575).

Special thanks to IREC and The University of Barcelona

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