Nitrogen-Doped Graphdiyne Nanotubes for Metal-Free Activation of Peroxymonosulfate and Enhanced Degradation of Recalcitrant Heterocyclic Contaminants

Abstract

Pollution removal via peroxymonosulfate (PMS)-mediated advanced oxidation processes provides an effective approach for water remediation. Although numerous carbon allotropes have been applied in PMS activation, the application of graphdiyne-based catalysts has been practically unexplored in this process despite their excellent electronic properties. In this study, the first instance of exploiting N-doped graphdiyne nanotubes (NGNTs) for metal-free PMS activation is presented to remove recalcitrant heterocyclic contaminants in aqueous environments. This mechanistic study demonstrates that the NGNT−PMS system decomposes heterocyclic contaminants via electron-transfermediated nonradical oxidation, where metastable NGNT−PMS* complexes were the primary oxidants. The apparent reaction rate constant for the NGNT−PMS system is 2.4 and 3.1 times higher than those for the counterpart systems by N-doped carbon nanotubes (NCNTs) and graphene oxide (NGO) systems, respectively. The NGNT exhibits excellent N-doping potential, demonstrated by a 7-fold increase in atomic nitrogen compared to NCNT in an identical Ndoping procedure. The possible N-doping sites in NGNT were determined as mainly sp-N-1, sp-N-2, pyridinic-N, amino-N, and graphitic-N atoms by the N K-edge X-ray absorption near-edge structure spectra and X-ray photoelectron spectroscopy. Theoretical calculations demonstrate the relatively obvious electron transfer between PMS and different N-sites in NGNT, indicating the possible formation of NGNT−PMS* complexes. Additionally, the NGNT−PMS system plays an important role in the cleavage of pyridine heterocycles and C−Cl bonds as demonstrated by the destruction of nitenpyram. This study provides mechanistic insights into the roles of NGNT in the metal-free activation of PMS for the remediation of recalcitrant heterocyclic contaminants.

Deciphering N-Doped Biochar Design for Non-Radical Pathways through Hierarchical Machine Learning

“…Metal-involved catalysts have the potential to produce both radical and nonradical species. , Graphitic carbon-based materials tend to mediate electron transfer, resulting in reaction progression via nonradical pathways . Nitrogen doping is commonly considered to be an effective method to optimize the electron configuration of carbonaceous materials, thereby enhancing their catalytic ability to promote 1 O 2 generation from PS. , N-doped biochar (NBC) is the most commonly utilized method for carbon-based catalyst modification, with the active sites on the surface of NBC significantly promoting the generation of radical and nonradical species, further accelerating the degradation of pollutants . It has been shown that NBCs give better catalytic performance for tetracycline degradation of persulfate compared to that of typical graphitic carbon (graphite powder, graphene oxide and multiwalled carbon nanotubes) .…”

Sustainable and Rapid Water Purification at the Confined Hydrogel Interface

“…[12] PS-AOPs are generally derived by activating peroxymonosulfate (PMS) or peroxydisulfate (PDS) with additional energy sources or catalysts, such as heat, [15] photoexcitation, [16] microwave, [17,18] ultrasound, [19,20] electrical field energies, [21] heterogenous catalysts (i.e., transition metal oxide, metal-free material, and single-atom catalyst). [13,19,[22][23][24][25][26] Although a multitude of studies have exhibited the high efficiency of catalyst activation systems in laboratory conditions, they concurrently confront formidable challenges that bear implications for practical applications. These encompass the requirement for mitigating secondary contamination factors, notably toxic ions and dispersed nanoparticles, and augmenting persulfate (PS) utilization efficiency, which, as it currently stands, demands a PS dose roughly 100 times greater than the organic concentration.…”

High-Loading Single-Atom Ru Catalysts Anchored on N-Doped Graphdiyne/γ-Graphyne Quantum Dots for Selective Hydrodehalogenation and Hydrodearomatization

“…Many previous studies regarding SACs present the substrates based on sp 2 -hybridized carbon materials, e.g., nanotubes − and graphene. − However, sp-hybridized carbon-based substrates have rarely been studied in the synthesis of SACs. Graphdiyne and γ-graphyne, as artificial π-conjugated carbon allotropes, possess a 2D framework with sp 2 - and sp-hybridized carbon atoms. − Compared to sp 2 -hybridized carbon frameworks, the structural linearity of the carbon–carbon triple bond (sp-hybridized carbons) avoids the fluctuation arising from cis – trans isomerization and has small steric demands. , Importantly, the absence of hexagonal symmetry and two self-doped nonequivalent distorted Dirac cones endow graphdiyne and γ-graphyne with electronic conduction properties superior to those of sp 2 -hybridized carbons. , Previous studies also show that graphdiyne substrates are more appropriate for nitrogen-doping modification compared with graphene series materials . The abundant nitrogen sites on carbonaceous substrates were verified in previous studies to anchor atomically dispersed metal sites .…”