Nanoreactor of Fe, N Co-Doped Hollow Carbon Spheres for Oxygen Reduction Catalysis

Easy detection of S2- using oxidase-like nanozymes of Fe,N co-doped hollow mesoporous carbon nanospheres via colorimetric method

The excessive presence of S2- poses significant risks to human health and the environment. Therefore, the development of novel S2- sensing methods remains crucial in daily life. Herein, Fe-N hollow mesoporous carbon nanospheres (Fe-N HMCNSs), characterized by a high specific surface area and excellent stability, were successfully prepared. Further investigation revealed that the colorimetric substrates such as 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonate) (ABTS), o-phenylenediamine (OPD), and 3,3',5,5'-tetramethylbenzidine (TMB), can be effectively oxidized by Fe-N HMCNSs into colored products. Based on the oxidase-like activity of Fe-N HMCNSs, a facile colorimetric method for S2- assay was constructed for the first time. The recognition of S2- could be fulfilled by recording the absorbance intensity and observing color changes in nanozymes-based catalytic systems. This method is simple, cost-effective, and environment-friendly, offering a wide linear range (0.25-25 µM) and a low detection limit (42.2 nM) for S2- assay. Furthermore, integration of smartphone-based RGB analysis enabled the portable and convenient S2- sensing using the developed colorimetric sensor. The remarkable stability of Fe-N HMCNSs under harsh conditions endows their potential applications in the fields of food safety and environmental protection.

Confining Hollow CoSn(OH)6 Cubes Inside Polydopamine Nanotubes To Significantly Promote Fenton-like Catalysis for Water Treatment

Tubular nanoreactors, which exhibit a distinctive void-confinement effect, have become intriguing for their prospective applications in catalysis. However, rationally constructing these structures remains a formidable challenge, particularly in realizing a significantly synergistic catalytic enhancement. In this study, we present a reliable template polymerization-guided synthetic strategy, creating hollow CoSn(OH)6 cubes inside polydopamine (PDA) nanotubes (CoSn(OH)6@PDA NTs). This sample functions as a potent peroxymonosulfate (PMS) activator for toxic contaminant oxidation. Diverse reactive oxygen species produced within the nanotubes significantly enhance this efficiency. The exceptional catalytic property results from the rich active sites of CoSn(OH)6 and the distinct nanotubular structure, which concentrates reactants and benefits the mass transfer process. This research opens possibilities for developing high-performance and robust catalysts with spatial confinement effects, advancing water treatment technology.

Enhancing activity and stability of FeNC catalysts through co incorporation for oxygen reduction reaction

FeNC single atom catalysts (SACs) have attracted great interest due to their highly active FeN4 sites. However, the pyrolysis treatment often leads to inevitable metal migration and aggregation, which reduces the catalytic activity. Moreover, due to the Fenton reaction caused by FeNC in alkaline and acidic solutions, the presence of Fe and peroxide in electrodes may generate free radicals, resulting in serious degradation of the organic ionomer and the membrane. Herein, we report an original strategy of introducing Co single atoms into FeNC catalysts, forming atomically dispersed bimetallic active sites (FeCoNC) and improving the activity and stability of the catalyst. Benefiting from this strategy, FeCoNC catalyst exhibits excellent oxygen reduction reaction (ORR) activity in alkaline media (E1/2 = 0.88 V) and in acidic media (E1/2 = 0.77 V). As the cathode of Zn-air battery (ZAB), FeCoNC shows an excellent peak power density of 142.8 mW cm-2 and a specific capacity of 806.6 mAh/gZn. This work provides a novel avenue to optimize and enhance the ORR performance of atomic dispersed FeNC catalysts.