Double-Confined Ultrafine Cobalt Clusters for Efficient Peroxide Activation

Abstract

The construction of highly active catalysts presents great prospects, while it is a challenge for peroxide activation in advanced oxidation processes (AOPs). Herein, we facilely developed ultrafine Co clusters confined in mesoporous silica nanospheres containing N-doped carbon (NC) dots (termed as Co/NC@mSiO2) via a double-confinement strategy. Compared with the unconfined counterpart, Co/NC@mSiO2 exhibited unprecedented catalytic activity and durability for removal of various organic pollutants even in extremely acidic and alkaline environments (pH from 2 to 11) with very low Co ion leaching. Experiments and density functional theory (DFT) calculations proved that Co/NC@mSiO2 possessed strong peroxymonosulphate (PMS) adsorption and charge transfer capability, enabling the efficient O–O bond dissociation of PMS to HO• and SO4 •– radicals. The strong interaction between Co clusters and mSiO2 containing NC dots contributed to excellent pollutant degradation performances by optimizing the electronic structures of Co clusters. This work represents a fundamental breakthrough in the design and understanding of the double-confined catalysts for peroxide activation.

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

“…The degradation of CVOC waste gas was performed in AOP wet scrubber, which has been described in detail in our previous works. , By bubbling the corresponding chlorobenzene solution, the chlorobenzene gas stream was generated and then transferred into the liquid phase in the form of microbubbles. Flows and concentrations of the chlorobenzene gas stream were regulated by mass flowmeters.…”

“…Catalytic combustion of CVOCs in gas–solid reactions typically leads to catalyst deactivation by surface chlorination and the formation of highly toxic dioxins. Recently, advanced oxidation processes (AOPs) have been widely researched for VOC elimination in a wet scrubber due to the generation of highly reactive oxygen species (ROS) under mild conditions. − Compared to the catalytic combustion process, the removal of CVOCs in AOPs has the advantages of high efficiency, simple operation, low cost, and energy saving. , Moreover, the synergistic effect of ROS with different REDOX potentials can effectively promote the dechlorination of CVOCs and prevent the formation of polychlorinated byproducts from the electrophilic reaction . Unlike the sequential batch reaction of wastewater treatment in AOPs, CVOCs are continuously transferred to the liquid phase in the form of bubbles, requiring a higher activity and stability of heterogeneous catalysts to activate the peroxide.…”

“…The favorable interaction between nanoconfinement and transition state could lower the activation energy barrier of peroxide and alter the reaction pathways . We previously developed the ultrafine Co clusters confined in mesoporous silica nanospheres via a double-confinement strategy, which exhibited exceptional peroxymonosulfate (PMS) activation capability for the removal of refractory organic pollutants . However, the stability and recycling ability of the double-confined Co clusters were still not satisfactory.…”