Attuned band structure in triple S-scheme heterojunctions for naproxen degradation under visible light
Mope E. Malefane, Muthumuni Managa, Thabo T.I. Nkambule, Alex T. Kuvarega
Abstract
• Triple S-scheme is designed through band structure modulation for NPX degradation. • Four-component semiconductor heterojunctions charge transfer was confirmed. • Triple and quadruple S-scheme were described as novel heterojunctions. • Two reductive and oxidative sites improved OH • > • O 2 − > h + generation for NPX mineralization. • High catalyst stability despite leaching of Cu 3 (PO 4 ) 2 due to multiple active sites. The limited charge carrier separation and transportation in single semiconductor photocatalysts has lobbied research and development in rational design and fabrication of heterojunction photocatalysts which has become a hot topic in the last decade. In-depth investigation of a four-component semiconductors interfacial charge transfer analysis considering the contribution of all components was done for the first time to deduce triple S-scheme heterojunction. This work investigated four-component semiconductors (Cu 3 (PO 4 ) 2 , BaWO 4 , C-MgO and LDH) heterojunction photocatalyst formation by the solvothermal method for visible light degradation of NPX. The degradation rate of CBLM-B (0.0429 min −1 ) with high BaWO 4 content was two times the degradation rate of CBLM-A (0.0203 min −1 ) with high LDH/C-MgO content. XPS, electrochemistry, and band structure analysis were used to propose a triple S-scheme heterojunction with high electron mobility and charge separation that enhanced the formation of OH • > • O 2 − > h + species as supported by radical trapping experiments due to presence of two oxidative and two reductive sites for stable generation of ROSs. Internal electric field (IEF) and band bending modulated an S-S interfacial strategy at the three junctions. Cu leaching affected the catalyst stability, and NPX degradation pathways were investigated with QTOF-HPLC-MS. This work demonstrated band structure adjustment for design of highly efficient triple S-Scheme heterojunctions application in environmental pollution remediation as a new development to advance scientific knowledge on four-component heterojunctions which may also be described using the Z-scheme charge transfer model.