Enhanced photocatalytic performance of g-C3N4@Ce-Fe bimetallic oxide with Z-scheme heterojunction for rapid degradation of tetracycline and its photodegradation pathway

Abstract

The construction of Z-scheme heterojunction photocatalysts is a promising way to take full advantage of the high redox capacity of photogenerated carriers to solve environmental problems. In this work, Z-scheme porous carbon-nitride (CN) encapsulated Ce-Fe bimetallic oxide (CN@CFO) was constructed by in-situ polymerization method. The small-sized CFO was uniformly anchored in the structure of CN layer. The strong interactions between CN and CFO during the coupling process form the heterojunctions. This CN@CFO achieved a maximum degradation rate of 91.5 % for tetracycline (TC) within 21 min, which is 2.4 times more rapid than that of pure CN under the condition of less catalyst usage (0.125 g/L). ESR and the radical trapping results show that the active substance of the CN@CFO was mainly ·O2-, which is six times stronger than pure CN, indicating that the Z-scheme electron transfer is responsible for its high photocatalytic activity. Compared to CFO, the structure of CN@CFO enhances the stability of the catalyst in acidic solutions and significantly reduces the Fe spillover concentration after cycling. In addition, the possible degradation pathways of TC were investigated, and the bacterial culture experiment (against E. coli) demonstrates that TC was decomposed into eco-friendly substances.