Rational design of S‒scheme Cd0.5Zn0.5S/CeO2 heterojunction for enhanced photooxidation of antibiotics and photoreduction of Cr(VI)

Abstract

Current photocatalysts endowed with oxidation and reduction capabilities for pharmaceuticals and heavy metals removal face numerous challenges, such as a lack of sufficient reactive sites, poor electron-hole separation, and limited oxidation and reduction capabilities. In this study, we aimed to overcome these limitations by employing a simple solvothermal method to fabricate a novel S-scheme heterojunction, Cd0.5Zn0.5S/CeO2. The optimal Cd₀.₅Zn₀.₅S/CeO2 heterojunction achieved a maximum ciprofloxacin degradation efficiency of 86 % within 30 min, showing a remarkable improvement of 2.4 and 4.6 times compared to pristine Cd₀.₅Zn₀.₅S and CeO2, respectively. The heterojunction also demonstrated a remarkable 100 % photoreduction efficiency of Cr(VI) within 30 min, which is double the photodegradation performance of the individual materials. The combination of Cd₀.₅Zn₀.₅S with CeO2 to form the Cd₀.₅Zn₀.₅S/CeO2 S-scheme heterojunction effectively enhanced spatial photo-carrier separation and optimized the photo-redox capability, resulting in a substantial improvement in photocatalytic performance and stability. Through radical trapping experiments, the primary reactive species responsible for CIP degradation were identified as h⁺, OH•, and •O₂⁻. Additionally, e⁻ was determined to be the key species responsible for the photoreduction of Cr(VI). Based on these findings, we proposed a plausible photocatalytic reaction pathway for the simultaneous elimination of both CIP and Cr(VI). This study underscores the significant potential of the Cd0.5Zn0.5S/CeO2 S-scheme heterojunction for advanced wastewater treatment applications, highlighting its innovative approach and superior performance.