Síntese de carbonos porosos modificados com nitrogênio para aplicações ambientais: captura de CO2 e produção de H2

Abstract

This work presents the synthesis of nitrogen-doped porous carbons (NCs) using a solvent-free synthesis route aligned with the principles of Green Chemistry, known as mechanochemistry. The synthesized materials were evaluated on two fronts: as adsorbents for CO₂ capture and as supports for metal niobate nanocomposites (NC14@NbX, where X = Co, Cu, Ni, Mn) for water electrolysis. Initially, the NCs were obtained by the mechanochemical method using resorcinol (carbon precursor) and melamine (nitrogen precursor). The effect of varying the precursor proportions on the textural properties of the porous carbon was evaluated. The results indicated that the MCN14 compound showed the best textural results, exhibiting an average diameter (7.8 nm) and mesopore volume (0.24 cm3·g-1). In CO2 capture, nitrogen doping proved to be fundamental in increasing chemical affinity with the gas at low pressures, with the MCN14 material reaching a capacity of 2.3 mmol·g-1, higher than undoped carbon. As electrocatalytic support, the MCN14 conferred remarkable activity and exceptional stability to the nanocomposites for the Hydrogen Evolution Reaction (HER) and Oxygen Evolution Reaction(OER), especially in basic media. The NC14@NbMn and NC14@NbCo catalysts stood out for their favorable kinetics and, crucially, maintained stable performance for 100 hours of continuous operation. Durability was attributed to the support's nitrogen sites, which act as anchor points, preventing aggregation and leaching of the active phase. Thus, this study validates a sustainable synthesis route to produce carbon materials, demonstrating the dual role of nitrogen as an active site for CO2 adsorption and as a stabilizer for electrocatalytic phases, paving the way for the development of low-cost, highly durable systems for environmental and energy applications.