# Single‐Atom Cobalt Species on Curved Hollow Carbon Sphere: Breaking Linear Scaling Relationship Limitations in Electrocatalytic Deactivation of Dilute Antibiotic Pollutants

## TL;DR

A new cobalt-based catalyst breaks efficiency limits in removing trace antibiotics from water, offering a promising solution for pollution cleanup.

## Contribution

Introduces a curved hollow carbon support that enables single-atom cobalt to overcome linear scaling relationship constraints in electrocatalysis.

## Key findings

- Co1/N-HCS achieves 14.1 gFLO gCo−1 mass activity for florfenicol deactivation, surpassing existing catalysts.
- The hollow porous structure enhances fluid dynamics and enriches dilute pollutants, while the curved surface boosts proton transfer.
- Field tests show environmental stability and resistance to matrix interference in natural water samples.

## Abstract

Despite maximal atomic efficiency, single‐atom catalysts (SACs) are constrained by linear scaling relationships in electrocatalytic hydrodechlorination (ECHD), a process effective for antibiotic pollutant deactivation yet challenged by multi‐proton /electron transfer and dilute reactant conditions. Herein, a novel cobalt (Co)‐SACs consisting of single‐atom Co anchored on a nitrogen‐doped hollow porous carbon sphere (Co1/N‐HCS) is fabricated, which exhibits a remarkable mass activity of 14.1 gFLO gCo
−1 at −0.30 V toward florfenicol (FLO, a typical antibiotic pollutant), outperforming Co1/carbon black, Co nanoparticles/carbon black, and previously reported catalysts. Mechanistic studies reveal that the unique hollow porous architecture of N‐HCS facilitates fluid dynamic enhancement and localized adsorptive enrichment of dilute FLO, while its curved surface boosts proton transfer at Co1 through localized electric field enhancement. The dual enhancements enable Co1 to break the linear scaling relationship limitations. Field tests for Co1/N‐HCS in natural lake water demonstrate excellent environmental stability and matrix interference resistance. Furthermore, it could effectively deactivate dilute FLO (5 µmol L−1) while suppressing the emergence of antibiotic resistance gene, highlighting its prospect in antibiotic pollution remediation. This study introduces a paradigm‐shifting support architecture to transcend the SACs performance boundary, while pioneering the application of ECHD for antibiotic pollutant remediation.

A cobalt (Co)‐SACs consisting of single‐atom Co anchored on a nitrogen‐doped hollow porous carbon sphere (Co1/N‐HCS) is fabricated for electrocatalytic hydrodechlorination of dilute antibiotics. The hollow porous architecture of N‐HCS concentrates the antibiotics, while its curved surface promotes proton transfer at the Co1 site via localized electric field enhancement. The dual enhancements enable Co1 to break linear scaling relationship limitations.