DOI: https://doi.org/10.55373/mjchem.v27i2.10

Keywords: Photocatalysis; Z-scheme heterojunction; dye degradation; platinum; electron mediator

Abstract

A Z-Scheme heterojunction comprising photocatalysts Bi₂WO₆ and g-C₃N₄ doped with platinum was successfully synthesized by two distinctive methods, batchwise & one-step, to degrade a model pollutant, RR4 dye. Several instruments including FTIR, XRD, UV-VIS, photoluminescence (PL analysis), FESEM-EDX and photoelectrochemistry were used to characterize the sample obtained. FTIR spectra depicted intense sharp peaks at 810 cm⁻¹ which were assigned to s-triazine units of CN. The C-N stretching vibration mode was also detected in the region of 1200–1750 cm⁻¹. The crystallite sizes of the prepared photocatalysts were determined by XRD diffraction, where the Scherrer equation was applied to calculate the size. In XRD, the diffraction angles of Bi2WO6 were exhibited at 28.6⁰, 33.1, 47.4⁰, 56.2⁰, 59.1⁰, 69.2⁰ and 78.8⁰, and these angles were also seen in a variety of composites. From UV-Vis analysis, pristine Bi₂WO₆ had an absorption edge of approximately 443 nm, which corresponded to a band gap of approximately 2.6 eV. The absorption edge of pure g-C₃N₄ was at about 457 nm, corresponding to a band gap of 2.8 eV. Upon fabrication of the Z-scheme heterojunction, no band gap reduction occurred. All modified and unmodified Bi₂WO₆/g-C₃N₄ samples showed photocatalytic degradation efficiencies of up to 50 %, and the composites prepared by one-step and batchwise techniques (hereinafter referred to as PBCN (OS) and PBCN (B) respectively) achieved 80 % photodegradation of RR4 dye.