Electron Transfer Trade-offs in MOF-Derived Cobalt-Embedded Nitrogen-Doped Carbon Nanotubes Boost Catalytic Ozonation for Gaseous Sulfur-Containing VOC Elimination

Abstract

High-performance and robust catalysts act as core drivers for catalytic ozonation to eliminate gaseous sulfur-containing volatile organic compounds (VOCs). Herein, nitrogen-doped carbon nanotubes embedded with Co species (Co@NCNT) are synthesized by thermolysis of a ZIF-67/melamine mixture. The carbon-confinement effects in Co@NCNT not only improve the stability of Co species but also regulate the electronic structure of Co�C bonds, consequently synergistically improving the catalytic ozonation performance. The experimental results indicate that the Co@NCNT catalyst could still remove ∼86% of odorous methyl mercaptan (CH 3 SH) after running for 60 h at 25 °C under an initial concentration of 50 ppm CH 3 SH and 40 ppm ozone, relative humidity of 60%, and space velocity of 600,000 mL h −1 g −1 , outdistancing reported values under comparable reaction conditions. Detailed characterization and theoretical simulations reveal that the electronic metal−support interaction of Co�C bonds in Co@NCNT significantly adjusts the electronic structure of Co species, thereby promoting ozone-specific adsorption/activation to convert the surface atomic oxygen (*O ad ) and •OH/ 1 O 2 /•O 2 − . Also, the electrons obtained from CH 3 SH in the electron-poor center transferred through the C�Co bond bridge to maintain the redox cycle of �Co 0/2+ → �Co 3+ → �Co 0/2+ and realize the efficient and stable removal of CH 3 SH into CO 2 /SO 4 2− /H 2 O. This work demonstrates that MOF-derived materials with tunable electronic structures achieve the stable removal efficiency for gaseous sulfurcontaining VOCs via electron transfer trade-offs and provide potential candidate catalysts for the application of air purification.

Deep Oxidation of Chlorinated VOCs by Efficient Catalytic Peroxide Activation over Nanoconfined Co@NCNT Catalysts

“…This process can strengthen the bond between the negative potential PMS and the catalyst, thus improving the reaction rate. Figure c shows that the Co 2p spectra of Co@NCNT displayed two main peaks at the binding energy of 780.9 and 796.5 eV, along with the satellite peaks at 785.9 and 803.0 eV, a typical feature for Co 2+ . , Notably, another peak at 778.5 eV attributed to Co 0 was also observed. In contrast, Co@NCNS only exhibited characteristic peaks of Co 2+ at 781.3 eV.…”

“…However, Co@NCNS exhibited a lamellar structure like the pure g-C 3 N 4 , indicating that the doping of Co did not change the morphology of the carbon materials in an inert atmosphere (Figures S4 and S5). The carbonization of the lamellar g-C 3 N 4 and its transformation into the tubular Co@NCNT may be due to the catalytic effects of Co species in reducing atmosphere. , The ICP-OES results showed that the Co content of Co@NCNT was 28.4%. Figure c clearly shows that the dark contrasting NPs (20–30 nm) were uniformly distributed and wrapped in well-defined carbon nanotubes over Co@NCNT.…”

“…The carbonization of the lamellar g-C 3 N 4 and its transformation into the tubular Co@NCNT may be due to the catalytic effects of Co species in reducing atmosphere. 22,31 The ICP-OES results showed that the Co content of Co@NCNT was 28.4%. Figure 2c clearly shows that the dark contrasting NPs (20−30 nm) were uniformly distributed and wrapped in well-defined carbon nanotubes over Co@NCNT.…”

Heterogeneous Bismuth Oxide Assemblages for Use in Persulfate Activation via the Bi–O–O Bridge: Reactivity, Kinetics, and Bactericidal Mechanism

“…To further confirm the key role of the amorphous oxide layer in adsorbing PS to form the Bi–O–O bridge, DFT calculation was used to explore the adsorption behavior of PS on the catalyst surface. , As shown in Figure a,b, the adsorption of PS on pure crystal Bi metal with the change of relative energy is (Δ E ) = −5.87 eV, which is much higher than that on heterogeneous bismuth oxide assemblages ( E ad = −8.95 eV) (Figure c,d). This result shows that heterogeneous bismuth oxide assemblages have a specific adsorption effect on PS molecules, which is related to the formation of the Bi–O–O bridge.…”

Fe3C@C/CNT Hybrids Derived from Catalytic Pyrolysis of Lignite: Electrocatalysts for OER

“…In addition, it can be seen from Figure a that after pyrolysis of a single L component, only a wide peak appears near 24°, corresponding to the (002) crystal plane of amorphous graphite carbon, while a sharp characteristic peak appears at 26.4° for L­(K), corresponding to the (002) crystal plane of graphitic carbon. The SEM images of L and L­(K) (Figure S1) show that L produces amorphous carbon with smooth appearance and no carbon nanotubes are generated.…”