A study on singlet oxygen generation for tetracycline degradation via modulating the size of α-Fe2O3 nanoparticle anchored on g-C3N4 nanotube photocatalyst
Hongjie Zhu, Minghui Li, Luning Zou, Youyou Hu, Hongguo Hao, Jianmin Dou, Junjie Mao
Abstract
Photocatalysis is considered as an effective technique for mitigating ecological risks posed by residual tetracycline (TC). To improve the efficiency of this technique, it is necessary to enable photocatalysts to produce highly reactive species, such as singlet oxygen (1O2). However, due to the high activation energy of 1O2, photocatalysts can hardly produce 1O2 without assistance from external oxidants. Herein, we find that the size-reduced α-Fe2O3 nanoparticles (∼ 4 nm) that anchored on g-C3N4 nanotube (α-Fe2O3@CNNT) can spontaneously generate 1O2 for degradation of TC. In comparison, only hydroxyl radical (·OH) can be produced by g-C3N4 nanotube loaded with ∼ 14 nm α-Fe2O3 nanoparticles (α-Fe2O3/CNNT). Owing to the high reactivity of the 1O2 species, the photocatalytic degradation rate (Kapp) of TC with α-Fe2O3@CNNT (0.056 min−1) was 1.8 times higher than that of α-Fe2O3/CNNT. The experimental results and theoretical calculations suggested that reducing the size of α-Fe2O3 nanoparticles anchored on g-C3N4 nanotube decreased the surface electron density of α-Fe2O3, which induces the generation of high-valent Fe(IV) active sites over α-Fe2O3@CNNT and turns the degradation pathway into a unique 1O2 dominated process. This study provides a new insight on the generation of 1O2 for effective degradation of environmental pollutant.