Integration of Bi₂Ti₂O₇ and CaIn₂S₄ to Form a Z-Scheme Heterojunction with Enhanced Charge Transfer for Superior Photocatalytic Activity

The use of an effective photocatalyst is critical for the photocatalytic degradation of pollutants in water using visible light, which is an essential prerequisite for wastewater treatment. In this work, the Z-scheme heterostructure photocatalyst of Bi2Ti2O7/CaIn2S4 (BTO–CIS) with high effectiveness for the degradation of crystal violet was successfully synthesized using a two-step process combining hydrothermal treatment and coprecipitation. The BTO/CIS heterojunction demonstrated a high photocatalytic efficacy of 98.58% in degrading CV after 15 min of visible light exposure. In comparison, BTO and CIS individually degraded CV by up to 62.01 and 75.80%, respectively, though over an extended duration of 50 min. The combination of BTO and CIS results in an increase in the separation of charges at the interface, which ultimately leads to an increase in the efficiency of the catalyst. Furthermore, ESR measurements and quenching studies have identified hydroxyl radicals (•OH) and superoxide radicals (•O2–) as the main active species. Additionally, the BTO/CIS heterojunction exhibited significant degradation efficacy against ciprofloxacin and tetracycline. Furthermore, the synthesized Bi2Ti2O7/CaIn2S4 heterojunction demonstrated exceptional stability, which is advantageous for practical applications in wastewater treatment.