New Insights into the Generation of Singlet Oxygen in the Metal-Free Peroxymonosulfate Activation Process: Important Role of Electron-Deficient Carbon Atoms

Abstract

A nonradical oxidation process via metal-free peroxymonosulfate (PMS) activation has recently attracted considerable attention for organic pollutant degradation; however, the origin of singlet oxygen ( 1 O 2 ) generation still remains controversial. In this study, nitrogen-doped carbon nanosheets (NCN-900) derived from graphitic carbon nitride were developed for activation of PMS and elucidation of 1 O 2 production. With a large specific surface area (1218.7 m 2 g −1 ) and high nitrogen content (14.5 at %), NCN-900 exhibits superior catalytic activity in PMS activation, as evidenced by complete degradation of bisphenol A within 2 min using 0.1 g L −1 NCN-900 and 2 mM PMS. Moreover, the reaction rate constant fitted by pseudofirst-order kinetics for NCN-900 reaches an impressive value of 3.1 min −1 . Electron paramagnetic resonance measurements and quenching tests verified 1 O 2 as the primary reactive oxygen species in the NCN-900/PMS system. Based on X-ray photoelectron spectroscopy analysis and theoretical calculations, an unexpected generation pathway of 1 O 2 involving PMS oxidation over the electron-deficient carbon atoms neighboring graphitic N in NCN-900 was unraveled. Besides, the NCN-900/PMS system is also applicable for remediation of actual industrial wastewater. This work highlights the important role of electron-deficient carbon atoms in 1 O 2 generation from PMS oxidation and furnishes theoretical support for further relevant studies.

Identification of Fenton-like active Cu sites by heteroatom modulation of electronic density

“…S26 A ). This contradicts the previous findings that D 2 O is a promoter for singlet oxygenation because the lifetime of 1 O 2 in D 2 O is extended up to 10 times ( 47 , 48 ). Thus, 1 O 2 was not primarily responsible for BPA degradation under such conditions, indicating the existence of a secondary nonradical PMS activation pathway ( 49 , 50 ).…”

Almost 100 % Peroxymonosulfate Conversion to Singlet Oxygen on Single‐Atom CoN2+2 Sites

“…[7c] It is difficult to completely eliminate the effect of the simultaneous production of strong oxidizing COH which would mask and complicate the transformation. [9] Furthermore, the effect of carbon substrate on the Co-N active site is often overlooked. Graphene, [10a] carbon nanotubes, [10b] metal-organic frameworks (MOF), [10c] and carbon nitride [10d] have been widely employed as supporting catalysts, which play an important role in manipulating the electronic structure of the active sites and hence interactions with reactant.…”

Insights into the relationship of reactive oxygen species and anions in persulfate-based advanced oxidation processes for saline organic wastewater treatment

“…21,159 1 O 2 -Dominated oxidation processes were also reported in carbon/PS catalytic systems. 108,160–169 Yu and co-authors reported the 1 O 2 -dominated degradation process in the sludge-derived carbon/PMS catalytic system that showed excellent performance for BPA degradation. 123 It was found that the ketone structure in the carbon was the main active site for the formation of 1 O 2 , the reaction route of which is different from the above-mentioned O 2 ˙ − route (Fig.…”

“…Besides the ketone structure, carbon defects and electronegative N doping were also suggested as the active sites for activating PS to produce 1 O 2 . 161,170 However, the detailed catalytic mechanisms are still unclear. Recently, Luo and co-authors have found that the N-doped graphitic carbon/PMS system showed a 1 O 2 -dominated pathway for efficient BPA degradation.…”