Band gap narrowing ternary phosphorus-doped g-C3N4/Fe0@expanded graphite carbon layer hybrid composite for effective degradation of tetracycline via multiply synergistic mechanisms

Abstract

The wide band gap of g-C3N4 and severe aggregation of Fe0 adequately limit their applications. To address these two critical issues, novel ternary phosphorus-doped g-C3N4/Fe0 @expanded graphite carbon layer (P-CN/Fe0 @EGC) photocatalyst with extremely narrow band gap and significantly enhanced catalytic activity was in-situ synthesized. P-CN/Fe0 @EGC hybrid composite exhibited excellent photodegradation performance of tetracycline (TC) removal, which is 5.18 and 1.92 times higher than that of pristine g-C3N4 and Fe0, respectively. Enhancement in photocatalytic activity is evaluated via photoluminescence (PL), UV–vis DRS, XRD and electron spin resonance (ESR). A reasonable catalytic mechanism of P-CN/Fe0 @EGC is proposed. The multiply synergistic mechanisms of phosphorus-doped g-C3N4 (P-CN), Fe0 and expanded graphite carbon layer (EGC), as well as the strong reducibility of Fe0 were accounted for the expanded visible light absorption range. The even dispersion of Fe0 on porous and worm-like structured P-CN/EGC effectively and successfully avoided the decline in photocatalytic activity caused by aggregation of Fe0 nanoparticles. Compared with g-C3N4, the band gap of phosphorus-doped g-C3N4 was narrowed from 2.79 to 2.60 eV. It is worth noting that Fe0 plays an important role in accelerating electron transfer speed and efficiency between P-CN and EGC. The·O2− and h+ were the dominant active substances for TC degradation. Moreover, P-CN/Fe0 @EGC catalyst could be used repeatedly for at least 7 cycles with high TC removal efficiency. This study may pave a new way on designing high efficient ternary hybrid photocatalyst for antibiotic degradation.