Diffusion-triggered ultra-uniformly distributed cobalt single atoms in self-supporting cathode for boosted...

While the generation of hydrogen peroxide using metal single-atom catalysts provides a promising pathway toward sustainable water purification, the preparation processes require further optimization to achieve full dispersion and efficient utilization of active sites. In this study, a facile lidded pyrolysis strategy is developed to fabricate a self-supporting N-doped carbon nanofiber electrode with atomically dispersed CoN₄ sites (Co@N-CNFs) for electro-Fenton (EF) degradation of tetracycline hydrochloride (TCH). The method involves electrospun polyacrylonitrile nanofibers embedded with patchy Co precursors, where lidded pyrolysis promotes the diffusion of Co vapor and N-containing radicals, yielding well-dispersed CoN₄ sites throughout the nanofibers. The resulting Co@N-CNFs electrode exhibits a 59-fold enhancement in H₂O₂ yield and an 11-fold increase in current efficiency compared to pristine N-doped carbon nanofibers (N-CNFs). Combined experiments with theoretical simulations reveal that single-atom Co significantly enhances charge transfer and stabilizes the key intermediate *OOH, thereby facilitating H₂O₂ generation. Benefiting from efficient H₂O₂ generation, the Co@N-CNFs EF system achieved 99.6% TCH degradation in 5 min-a performance that far exceeds that of the N-CNFs control (26.4%) and most recently reported systems-via synergistic radical (O₂^•- and •OH) and non-radical (¹O₂) pathways. Furthermore, the Co@N-CNFs EF system demonstrates low-toxicity degradation byproducts, exceptional stability, broad applicability, and low energy consumption for antibiotic removal even in real wastewater matrices, highlighting its practical potential. This study presents a simple lidded pyrolysis method to fabricate self-supporting EF cathodes with ultra-uniformly distributed single-atom metal sites and offers a promising approach toward sustainable water purification technologies.