Nitrogen-doped carbon materials demonstrate high performance as electrodes in fuel cells and higher oxygen reduction reactivity than traditional Pt-based electrodes. However, the formation process of nitrogen-doped carbon materials has long been a mystery. In this study, the formation mechanism of nitrogen-doped carbon materials from polyaniline (PANI) pyrolysis was studied by the combination of in situ pyrolysis vacuum ultraviolet photoionization time-of-flight mass spectrometry (Py-VUVPI-TOF MS) and substrate-enhanced, laser-induced acoustic desorption source time-of-flight mass spectrometry (SE-LIAD-TOF MS). The initial pyrolysis species, including free radicals and intermediates, were investigated via in situ Py-VUVPI-TOF MS during the temperature-programmed desorption process (within tens of microseconds). The pyrolysis residues were collected and further investigated via SE-LIAD-TOF MS, revealing the product information of the initial pyrolysis products. The results show that the edge doping of carbon materials depends on free radical reactions rather than the direct substitution of carbon atoms by nitrogen atoms. Meanwhile, pyrrole nitrogen and pyridine nitrogen are formed by the free radical cyclization reaction and the amino aromatization reaction at the initial stage of pyrolysis, while the formation of graphitic nitrogen depends on the further polymerization reaction of pyrrole nitrogen and pyridine nitrogen.

Although cyclopentanone (CPO) is a promising bio-derived fuel, thermodynamic data of its low-temperature oxidation under high-pressure conditions are lacking. In this work, the low-temperature oxidation mechanism of CPO is investigated in a flow reactor in the temperature range of 500-800 K and at a total pressure of 3 atm by a molecular beam sampling vacuum ultraviolet photoionization time-of-flight mass spectrometer. The electronic structure and pressure-dependent kinetic calculations are carried out at the UCCSD(T)-F12a/aug-cc-pVDZ//B3LYP/6-31+G(d,p) level to explore the combustion mechanism of CPO. Experimental and theoretical observations showed that the dominant product channel in the reaction of CPO radicals with O₂ is HO₂ elimination, yielding 2-cyclopentenone. The hydroperoxyalkyl radical (^•QOOH) generated by 1,5-H-shifting is easily reacted with second O₂ and forms ketohydroperoxide (KHP) intermediates. Unfortunately, the third O₂ addition products are not detected. In addition, the decomposition pathways of KHP during the low-temperature oxidation of CPO are further assessed, and the unimolecular dissociation pathways of CPO radicals are confirmed. The results of this study can be used for future research on the kinetic combustion mechanisms of CPO under high pressure.