Ni2P-CoxP/U-ZrO2/C NFs heterojunction photocatalyst for efficient and stable degradation of PET waste under visible light

Abstract

Petroleum-derived PET plastics and fibers are widely used in packaging and textile fields due to their superior properties and have become a major source of plastic waste. In this study, Ni₂P-Co_xP/ZrO₂/C NFs p-n heterojunction photocatalytic system with the UiO-66-NH₂ metal-organic backbone (MOFs)-derived ZrO₂ (U-ZrO₂) was constructed by a combined method of electrospinning, carbonization, hydrothermal, and phosphorization process. Carbon nanofibers are used as carriers to combine the different components effectively. The Ni₂P-Co_xP/U-ZrO₂/C NFs show strong light absorption ability throughout the entire visible light region. The needle-shaped structure of Ni₂P-Co_xP can provide abundant active sites, increase the reflection of light on the fiber surface, and promote the utilization of light by the photocatalyst. With the incorporation of the MOF structure, the specific surface area of the fibers was greatly enhanced. The coupling of Co_xP with Ni₂P and U-ZrO₂ establishes a p-n heterojunction at the photocatalytic interface, which promotes the separation efficiency of photogenerated carriers and prolongs the charge lifetime while maintaining the strong redox capacity of the catalyst, enhancing the photocatalytic degradation activity. The MOF-derived ZrO₂ still maintains an octahedral shape, which favors the attachment of Ni₂P and Co_xP. As a result, the hydrogen production of the system reached 303.64 $\text{μ}\text{mo}{\text{l}}_{{\text{H}}_2}{\text{g}}_{\text{Sub}}^{-1}$ after 24 h, and the weight loss rate of PET reached 18.77 ± 4.28 %. Besides, the reusability of the catalyst was greatly improved by re-phosphorization of the used catalyst, which enables it to recover its catalytic degradation efficiency. This work provides new insights into the rational design of heterojunction photocatalysts with superior degradation performance.