Highly efficient photodegradation of methylene blue by a composite photocatalyst of bismuth nanoparticles on silicon nanowires

Abstract

When synthetic dyes are used to embellish the world, the wastewater holding these hazardous materials is wantonly released into the biosphere. Appropriate treatment for such effluents is thereby indispensable. In this context, the present study was conducted to fabricate an eco-friendly, cost-effective and new bismuth modified silicon nanowires (Bi@SiNWs)-based photocatalysts toward superior photocatalytic degradation of methylene blue (MB) dye under both UV and solar irradiations. SiNWs were synthesized by silver-assisted chemical etching while Bi nanoparticles were anchored onto the NWs via thermal evaporation. By assessing the morphology, elemental composition, structure and crystallinity characteristics, these Bi@SiNWs nanocomposites are systematically identified. Extensive investigations of blank SiNWs and Bi@SiNWs optical properties — reflectance, transmittance, absorption coefficient, absorbance and optical band-gap — are presented. Near-perfect absorbance above 97%, over the visible wavelength region, has been achieved owing to the synergistic effect of Bi decoration on SiNWs. Accordingly, Bi@SiNWs showed remarkable photocatalytic ability for the degradation of MB up to 44% and 89% under UV and solar irradiation, respectively, only within 120 min. Repeated cycle runs revealed that the Bi@SiNWs composite photocatalyst exhibits strong reusability and photo-stability. Lastly, we will thoroughly provide the plausible mechanism for the photocatalytic degradation of MB over Bi@SiNWs. Our outcomes validate the potent role of Bi@SiNWs photocatalysts for effective environmental remediation. • A new Bi-modified SiNWs active photocatalyst was successfully synthesized. • Bi@SiNWs showed near-perfect absorbance feature to above 97%. • Photocatalytic performance of pure MB dyes, SiNWs and Bi@SiNWs under UV and solar irradiations were studied. • Bi@SiNWs exhibited the highest photocatalytic degradation of MB up to 89% under solar irradiation. • Cycling capability, photocatalysis mechanism and reactions kinetics of MB decomposition over Bi@SiNWs were investigated.