Simple tactic polycondensation synthesis of Z-scheme quasi-polymeric g-C₃N₄/CaFe₂O₄ composite for enhanced photocatalytic water depollution via p-n heterojunction

Ferrites are promising photocatalysts as they absorb a considerable fraction of visible light. Herein, a novel in-situ simple tactic polycondensation method was used to produce n-type porous graphitic carbon nitride nanosheets over p-type CaFe₂O₄ particles resulting in a “quasi-polymeric” heterojunction. An interfacial electron trap state was created, as represented by an energy-resolved distribution of electron trap patterns in the g-C₃N₄/CaFe₂O₄, which traps excited electrons and prevents charge carrier recombination. When the CaFe₂O₄ precursor content in the g-C₃N₄/CaFe₂O₄composite was optimized, the degradation rates of ciprofloxacin and phenol are 2.3 and 2.1-fold higher in comparison to pristine g-C₃N₄, respectively. The g-C₃N₄/CaFe₂O₄ composite efficiently absorbed visible light and could separate and transport charge carriers through the p-n heterojunction. The efficient interfacial charge transport and separation achieved in the composite were validated using photoluminescence spectra and photoelectrochemical characterizations. Based on scavenger studies and electron spin resonance analysis, the most active radical species for the aforementioned pollutant degradation are holes and superoxide anion radicals. Mott-Schottky measurements and X-ray photoelectron spectroscopy confirmed the photocatalytic reaction mechanism is a Z-scheme charge carrier transport route based on the p-n heterojunction. Therefore, the g-C₃N₄/CaFe₂O₄ heterojunction offers a lot of promise for pollutant degradation that is both efficient and long-term.