Pyrolysis of folic acid: Identification of gaseous/volatile products and structural evolution of N-doped graphitic carbon

Author(s)

Magri, Vagner R. ; de Matos, Caroline S. ; Rocha, Michele A. ; Taviot-Gueho, Christine ; Constantino, Vera R. L.

• Document type: Journal article
• Source: Thermochimica Acta; v. 739, p. 11-pg., 2024-07-19.

Abstract

Folic acid (FA) is a low-cost and suitable source for producing different N-doped carbon materials by pyrolysis. However, the pyrolytic steps of FA are not entirely understood, particularly above 350 degrees C, which hampers the intelligent design of tailor-made carbon materials by a one-pot route. In this work, the pyrolytic decomposition steps of FA were investigated by simultaneous thermogravimetric analysis (TGA) and differential scanning calorimetry (TGA-DSC). The released gaseous/volatile products were probed by coupling TGA to infrared spectroscopy and mass spectrometry (TGA-FTIR-MS). Considering the thermal analysis data, FA was pyrolysed in a furnace at 350, 430, 570, 800, and 1000 degrees C, and the products were analysed by X-ray diffractometry (XRD), vibrational spectroscopy, and X-ray photoelectron spectroscopy. In situ high-temperature X-ray diffractometry (HT-XRD) experiments were also conducted under the nitrogen atmosphere. According to the data set, insights about FA decomposition steps could be proposed, including gaseous/volatile products released during the process and the structural evolution of N-doped graphitic carbon. The formation of carbonaceous material initiated between 200 and 350 degrees C through polymerisation/condensation reactions, and this step was marked by the release of 2-pyrrolidone and aniline. The graphitisation was enhanced above 350 degrees C, increasing graphitic nitrogen while the amide groups vanished. The process was accompanied by deoxygenation (i.e., CO and CO2 release) and denitrogenation (e.g., NH3, HNCO, and HCN) reactions. In the 570-800 degrees C range, the N-enrichment of carbon material (N-pyridine, N-pyrrole/Csp2-N in 5,7-membered rings, and nitrile) could occur by the reaction of released NH3 over the char surface. Graphitic-like structures containing mainly N-graphite and N-pyridine were obtained above 800 degrees C. The original data about the thermal decomposition steps of FA allow for optimising the synthesis of N-doped carbon materials suitable for applications in adsorption, sensing, catalysis, and energy storage. (AU)

• FAPESP's process: 14/50869-6 - INCT 2014: on Organic Electronics
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 12/06291-4 - Synthesis and characterization of hybrid materials based on layered double hydroxides and bioactive organic species
• Grantee: Caroline Silva de Matos
• Support Opportunities: Scholarships in Brazil - Scientific Initiation