Tuning Band Gap in Fe-Doped g-C3N4 by Zn for Enhanced Fenton-Like Catalytic Performance

Zn2+ was facilely introducedin Fe-doped g-C3N4, which showed more outstandingcatalytic performancethan those of similar catalysts reported. The catalytic mechanismwas proposed. Multipleoxidation states of first-row transition-metal cationswere always doped in g-C3N4 to enhance the catalyticactivity by the synergistic action between the cations in the Fenton-likereaction. It remains a challenge for the synergistic mechanism whenthe stable electronic centrifugation (3d (10)) of Zn2+ was used. In this work, Zn2+ wasfacilely introduced in Fe-doped g-C3N4 (named xFe/yZn-CN). Compared with Fe-CN, the rateconstant of the tetracycline hydrochloride (TC) degradation increasedfrom 0.0505 to 0.0662 min(-1) for 4Fe/1Zn-CN. Thecatalytic performance was more outstanding than those of similar catalystsreported. The catalytic mechanism was proposed. With the introductionof Zn2+ in 4Fe/1Zn-CN, the atomic percent of Fe (Fe2+ and Fe3+) and the molar ratio of Fe2+ to Fe3+ at the catalyst's surface increased, whereFe(2+) and Fe3+ were the active sites for adsorptionand degradation. In addition, the band gap of 4Fe/1Zn-CN decreased,leading to enhanced electron transfer and conversion from Fe3+ to Fe2+. These changes resulted in the excellent catalyticperformance of 4Fe/1Zn-CN. Radicals center dot OH, center dot O-2 (-), and O-1(2) formed in thereaction and took different actions under various pH values. 4Fe/1Zn-CNexhibited excellent stability after five cycles under the same conditions.These results may give a strategy for synthesizing Fenton-like catalysts.

Automated summary

This study demonstrates that the introduction of Zn2+ in Fe-doped g-C3N4 can improve the catalytic performance, and a catalytic mechanism is proposed. The synergy between first-row transition-metal cations doped in g-C3N4 enhances the catalytic activity. However, the stable electronic centrifugation of Zn2+ poses a challenge to the synergistic mechanism. Compared to Fe-CN, the introduction of Zn2+ in 4Fe/1Zn-CN increases the degradation rate constant of tetracycline hydrochloride (TC). The increased atomic percent of Fe (Fe2+ and Fe3+), the molar ratio of Fe2+ to Fe3+, and the decreased band gap contribute to the excellent catalytic performance of 4Fe/1Zn-CN. The radicals ·OH, ·O-2 (-), and O-1(2) play different roles under different pH conditions. Additionally, 4Fe/1Zn-CN exhibits excellent stability after five cycles. These findings provide a strategy for synthesizing Fenton-like catalysts.