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

Abstract

Multiple oxidation states of first-row transition-metal cations were always doped in g-C3N4 to enhance the catalytic activity by the synergistic action between the cations in the Fenton-like reaction. It remains a challenge for the synergistic mechanism when the stable electronic centrifugation (3d10) of Zn2+ was used. In this work, Zn2+ was facilely introduced in Fe-doped g-C3N4 (named xFe/yZn-CN). Compared with Fe-CN, the rate constant of the tetracycline hydrochloride (TC) degradation increased from 0.0505 to 0.0662 min-1 for 4Fe/1Zn-CN. The catalytic performance was more outstanding than those of similar catalysts reported. The catalytic mechanism was proposed. With the introduction of 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, where Fe2+ and Fe3+ were the active sites for adsorption and 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 catalytic performance of 4Fe/1Zn-CN. Radicals •OH, •O2-, and 1O2 formed in the reaction and took different actions under various pH values. 4Fe/1Zn-CN exhibited excellent stability after five cycles under the same conditions. These results may give a strategy for synthesizing Fenton-like catalysts.