Iron nanoparticles enhance the efficiency of single-atom Fenton-like catalyst by boosting Fe-NX activity

Single-atom catalysts (SACs) have been widely employed for the removal of organic contaminants via advanced oxidation processes (AOPs). The underlying principle involves central metal atoms that interact synergistically with surrounding atoms in specific ensembles to adsorb reactants and facilitate catalytic reactions. However, comprehensive studies exploring the ensemble effect of SACs in combination with metal nanoparticles relatively rare. In this study, we have synthesized a highly active iron single-atom catalyst (Fe@BC), which features both Fe-Nx coordination sites and iron nanoparticles. Fe@BC exhibits remarkable adsorption and degradation capabilities for bisphenol A across a wide pH range from 3.0 to 11.0. Scavenging experiments coupled with electron paramagnetic resonance analysis have revealed that (OH)-O-center dot and O-2(center dot-) are the key reactive oxygen species within the Fe@BC/PAA system, with (OH)-O-center dot playing a crucial role in the removal of bisphenol A (BPA). Our comprehensive characterization analysis has validated the simultaneous presence of Fe nanoparticles and Fe-Nx sites, which are crucial for the catalyst's high activity. Furthermore, our experimental data highlight the importance of the synergistic effect between these two components. Density Functional Theory calculations have provided additional insights, showing that the presence of iron nanoparticles significantly boosts the Fe-Nx sites' activity. This enhancement is achieved by increasing adsorption energy, promoting electron transfer to peracetic acid (PAA), and decreasing the energy barrier for the formation of active species. These findings are vital for the strategic refinement of Fe single-atom catalysts for PAA-based advanced oxidation processes.