Highly efficient and continuous activation of O2 by a novel FexP-FeCu composite for water purification and insights into the activation mechanisms through DFT calculation.

Degradation of organic pollutants through O₂ activation catalyzed by transitional metals is challenging without addition of external chemicals and input of energy. We prepare a novel Fe based catalyst by compositing carbon, iron phosphide (Fe_xP), iron carbide (Fe_xC), Fe⁰ and Cu NPs, which can continuously activate O₂ to produce high amount of ¹O₂,·O₂^- and·OH radicals in a wide pH range. DFT calculation discloses that O₂ molecules are dissociated into *O or exist as O-O in various configurations. The Fe-O₂, Cu-O₂ and FeP-O₂ surfaces can react with H₂O molecules to generate *OOH, *OH and/or OH^-. The sorbed-O₂ intermediates on Fe_xC surface might be released as ¹O₂ or·O₂^-. The oxidative O₂-sorbed surfaces and in-situ produced oxygen reactive species contribute to the efficient and pH-indenpendent degradation of organic pollutants. Cu NPs accelerate Fe²⁺/Fe³⁺ cycles and offer impetus to initiate O₂ activation due to the potential difference between Fe and Cu. The recycling test and XPS results confirm that the mutual electron transferring among carbon, Fe_xC, Fe_xP, Fe and Cu maintains reactivity and stability of the catalysts.