Electrocatalysis for the production of ammonia from nitrogen: elucidation of the mechanism of the reduction reaction on Rh and Ru nanocatalysts.

• Grant number: 24/05966-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: May 01, 2025
• End date: November 30, 2027
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
• Principal Investigator: Joelma Perez
• Grantee: Rodrigo Gomes de Araujo
• Host Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 19/22183-6 - Electrocatalysis VI: fundamental and applied aspects of emerging and classical problems in electrochemical energy conversion, AP.TEM

Abstract

Conventionally, the Haber-Bosch process to produce ammonia uses hydrogen derived from the steam reforming of methane, consequently resulting in the emission of greenhouse gases into the atmosphere. As an alternative to the Haber-Bosch process, the nitrogen reduction reaction (NRR) for ammonia under ambient temperature and pressure conditions has gained prominence as it drastically reduces CO2 emissions, mainly due to competition with the hydrogen evolution reaction. Most of the experimental studies on NRR focus on the quantification of ammonia production, mechanistic proposals, and possible reaction intermediates are presented in theoretical works that involve calculations of density functional theory (DFT). In this project, Rh and Ru nanoparticles will be studied using several techniques to understand NRR. These materials will be supported on high surface area carbon, graphenes, and MoS2. In addition, an additional approach will involve modifying these materials with Fe and Cu. The most promising catalysts will be evaluated as cathodes in electrolyzers. The prepared nanocatalysts will be characterized by physical techniques such as transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. The electrochemical responses of the NRR will be accompanied by cyclic and linear voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Several techniques will be employed to analyze gaseous products, in solution and adsorbed intermediates, to propose a mechanism for NRR. Among these techniques are mass spectroscopy for analyzing gaseous products, UV-Vis spectroscopy, and ion chromatography for analyzing products in solution, and Raman spectroscopy and Fourier transform infrared spectroscopy for analyzing adsorbed products. In-depth experimental investigation on these surfaces will allow the elucidation of the mechanism for large-scale ammonia production to occur sustainably through NRR.