Hybridization of SrTiO3 and strontium wolframates with very-high-potential photogenerated carriers for degrading the A-ring of tetracycline

Abstract Degrading the A-ring of tetracycline (TC) requires a photocatalyst with either a very negative conduction band edge (CBE) or a very positive valence band edge (VBE). In this work, a SrTiO3-based composite with a Sr/W ratio of 7.5% (CSWT75) was prepared by hybridizing the following components: n-type semiconductor Sr2WO5 with CBE of –2.10 V, n-type semiconductor SrWO4 with a VBE of 4.42 V, and p-type semiconductor Sr3WO6 with CBE of–1.26 V, resulting in formation of z-scheme and p-n heterojunctions. Over CSWT75, the photodegradation rate of the B, C, and D rings of TC was 100% in 60 min and that of A ring was 98% in 90 min. The reaction rate constant of CSWT75 was found to be 3.4-fold that of the as-prepared pure SrTiO3. It is found that a high positive VBE potential like that of SrWO4 4.42 V is more effective on degrading A-ring than a negative CBE potential −0.81 of SrTiO3, but less effective than a negative CBE potential −1.26 V of Sr3WO6. This study identified two new semiconductors with highly negative CBEs. This work also implys that a z-scheme structured composite hybridizing homeotype-semiconductors with very negative CBE favors in degrading A ring of TC.