Direct transformation of bulk cobalt foam into cobalt nanoparticles encapsulated in nitrogen-doped carbon nanotubes for peroxymonosulfate activation toward rhodamine B degradation

A simple, efficient and straightforward method was developed to synthesize Co/NCNT via the direct transformation of bulk cobalt foam into cobalt nanoparticles encapsulated in NCNT. The optimal Co/NCNT-700 delivered the highest performance for peroxymonosulfate activation with sulfate radical (SO4·−) and singlet oxygen (1O2) as the main ROS for RhB degradation. [Display omitted] •Direct transformation of Co foam into cobalt NPs encapsulated in NCNT is achieved.•Co/NCNT-700 exhibits the optimal performance for PMS activation to degrade RhB.•Catalytical mechanism of sulfate radical and singlet oxygen is verified.•Pyridinic N, sp2-hybrid carbon, ketonic groups and Co species are the active sites. Supported cobalt (Co)-based materials have attracted widely attention owing to their effectiveness in activating peroxymonosulfate (PMS) for remediation of organic pollutants. Nevertheless, traditional synthetic strategies for these materials usually need complex steps and lack suitable interaction between Co and support. Herein, we develop a simple, convenient, and straightforward approach to prepare encapsulated Co nanoparticles (NPs) through direct atom emitting from Co foam, and subsequent trapping on nitrogen-doped carbon nanotubes (NCNT) with the aid of melamine. The as-prepared Co/NCNT can be used as an excellent catalytic material for PMS activation to efficiently degrade rhodamine B (RhB), among which the Co/NCNT-700 exhibits the optimal performance (rate constant:1.561 min−1). This magnetic material can be easily isolated and reused for five times with high removal efficiency. The quenching tests and electron spin resonance (ESR) characterization unveil the catalytical mechanisms of sulfate radical (SO4·−) and singlet oxygen (1O2) for RhB degradation. Combined with XPS analysis and other characterization findings, pyridinic nitrogen, sp2-hybrid carbon, ketonic groups, and Co species are the possible catalytic active sites of Co/NCNT-700. This approach is easily scalable and has been verified as a feasible way for synthesizing metal–carbon materials toward efficient degradation of organic pollutants in complex water systems.