Photocatalytic degradation of phenol wastewater over Z-scheme g-C ₃ N ₄ /CNT/BiVO ₄ heterostructure photocatalyst under solar light irradiation

A series of carbon nanotubes (CNT) modified g-C ₃ N ₄ /BiVO ₄ photocatalysts were synthesized via wet-impregnation method and evaluated via degradation of phenol under solar light irradiation. The physicochemical properties of the as-developed photocatalyst were characterized using FTIR, XRD, FESEM, XPS, SAP and DR-UV Vis. The formation of g-C ₃ N ₄ /CNT/BiVO ₄ photocatalysts resulted in remarkable enhancement in the performance in which almost six times higher degradation rate in comparison to the pristine g-C ₃ N ₄ and obeyed the pseudo-first-order kinetics and Temkin adsorption model. Congruously, the synergistic interaction between 2 wt% of CNT and 5 vol% of H ₂ O ₂ as an oxidizing agent was capable of removing 80.6% of phenol within 120 min. The profound photodegradation performance monitored was attributed to the better crystallinity structure obtained as shown in XRD and XPS analysis. Furthermore, the intimate contact between the CNT, g-C ₃ N ₄ and BiVO ₄ in the heterostructure sample as shown in FESEM micrograph images does help in allowing a smooth electron-hole pair separation and migration, resulting in more available •OH and •O ₂ ^¯ radicals for photocatalytic degradation activities. The possible Z-scheme reaction mechanism has been proposed and active species trapping experiments have been carried out to find the role of active radical species responsible for the phenol degradation. Additionally, the g-C ₃ N ₄ /CNT/BiVO ₄ photocatalysts retained excellent stability even after several cycles. Congruently, a mathematical representation for understanding the interaction between CNT loading and H ₂ O ₂ for photodegradation of phenol using response surface methodology (RSM) was successfully generated.