Unprecedented Nonphotomediated Hole (h⁺) Oxidation System Constructed from Defective Carbon Nanotubes and Superoxides

Abstract

Holes ( h + ) on heterogeneous photocatalysts could act as important oxidative species or precursors for reactive oxygen species (ROS). However, due to the ultrafast recombination of photoinduced electrons and holes, a majority of carriers are consumed prior to surface reactions. Herein, we report an unprecedented nonphotomediated hole oxidation system constructed from carbon nanotubes (CNTs) and superoxides. This system exhibited high catalytic activity for the degradation of organic pollutants, which outperforms the classical oxidation processes in the remediation of actual wastewater and is comparable to that of the best single cobalt atom catalyst. Theoretical and experimental results reveal that the intrinsic defects with unpaired spins on CNTs served as adsorptive sites to activate superoxides. This is the first report on exploring the oxidation properties of nonphotomediated hole carriers on heterogeneous catalysts, which will be of broad interest for researchers in environmental remediation, chemical synthesis, and biological fields.

An ultrafast and facile nondestructive strategy to convert various inefficient commercial nanocarbons to highly active Fenton-like catalysts

“…5 ). As demonstrated in our previous work ( 23 ), the electrons localized at the highest occupied molecular orbital (HOMO) (−4.76 eV; defined by the work function) of CNT could be injected into the lowest unoccupied molecular orbital (LUMO) of PS (−6.46 eV) due to the energy gap, which induces the generation of holes with oxidation capabilities on CNT. And if more electrons could be extracted by PS, more holes will be generated on CNT, and higher pollutant-removal efficiency will eventually be achieved.…”

“…S11 , increasing the amount of doped PEI does not induce the enhancement of catalytic performance of MWCNT, indicating that the amine nitrogen (–NH 2 ) species introduced by PEI are not the active sites. Previous studies have suggested that defects (edges and/or vacancies) could act as active sites for PS activation ( 21 , 23 ). To examine the role of defects in PEI-MWCNT on the catalytic performance, MWCNTs containing different contents of defects were functionalized by PEI and applied to activate PS for BPA degradation ( SI Appendix , Fig.…”

“…Furthermore, in order to avoid recycling the dispersed catalysts, membranes were fabricated in situ in a membrane reactor according to our previous report ( 23 ). The resultant membranes are 12.56 cm 2 in size and can be easily scaled up (the photographs inserted in SI Appendix , Fig.…”

“…In general, the efficiencies of pristine nanocarbons in activation of PS are very low ( 19 , 20 ). Researchers have successively explored different strategies to boost the PS activation by regulating the local electronic environment of carbocatalysts, such as covalent doping of suitable heteroatoms (e.g., N or S) ( 17 , 21 , 22 ), introduction of intrinsic defects on the edge ( 23 , 24 ), and construction of specific structure ( 25 ). However, the existing strategies usually involve complicated preparation processes (the usage of templates), special equipment (plasma devices), and/or harsh reaction conditions (high-temperature annealing under special atmosphere), which are time-consuming and more laborious, greatly increasing the financial costs for large-scale production and industrialization ( 22 , 25 , 26 ).…”

Carbon Nanotubes Induce Metabolomic Profile Disturbances in Zebrafish: NMR-Based Metabolomics Platform

“…In the past few decades, the carbon nanotubes (CNT) have gained a great attention in biomedical applications that are observed as pipe-shaped atomic layers of carbon particles. It is made up of layerby-layer orientation of graphite sheets (Cheung et al, 2000;Wang et al, 2021;Zhou et al, 2021). Single-walled carbon nanotubes (SWCNT) and multi-walled carbon nanotubes (MWCNT) have recently applied in lung cancer therapy as a novel drug delivery system, with topographies ranging from 10 to 1,000 nm in size and length ranging from 0.5 to 20 nm.…”