Improved photocatalytic activity of ZnO-[10%]BiOI and ZnO-[10%]WO3 heterostructure in the destruction of 2-chlorobiphenyl

Abstract

A series of photocatalysts and heterojunction composites comprising ZnO, WO₃, and BiOI with different loadings of WO₃ and BiOI into ZnO was synthesized and applied for the destruction of 2-chlorobiphenyl (2CBP). The surface morphologies and elemental analysis of the as-synthesized composites were determined using a Carl Zeiss Sigma FE-SEM equipped with an Oxford X-act EDS; optical studies were conducted using a UV 1800 Shimadzu UV-vis spectrophotometer. The X-ray diffraction measurements were made with a Bruker D2 XRD instrument, while the BET surface area measurements, BJH pore size distribution, and isotherms were obtained using a Micrometrics TriStar 3000 instrument. The ZnO-[10%]BiOI heterostructure exhibited a superior photocatalytic activity in this study. The degradation reactions were fitted to the pseudo-first and second order kinetic models in order to exploit the kinetic process of the photodegradation reaction. The ZnO-[10%]BiOI hetero-photocatalyst showed the highest rate constants of 0.0054 min⁻¹ and 0.0086 min⁻¹ in both the first and second order kinetic models, respectively. When compared to undoped ZnO, the rate constant of the ZnO-[10%]BiOI heterostructure was observed to be nearly 5-fold higher, demonstrating the superior catalytic performance of the as-prepared ZnO-[10%]BiOI hetero-structured photocatalyst. All the photocatalysts and heterostructures showed increased rate constants in the second-order reaction kinetics model except for BiOI and ZnO-[5%]WO₃, whose rate constants decreased from 0.0046 to 0.0041 min⁻¹ and 0.0036 to 0.0029 min⁻¹, respectively. The kinetic data show that it requires 128.4 min for the measured 2CBP concentration to be halved to the initial concentration when ZnO-[10%]BiOI is applied. A charge separation degradation mechanism is proposed to describe the process. The findings from this study suggest that ZnO-[10%]BiOI can potentially be used as an efficient and effective catalyst for the degradation of recalcitrant organic pollutants in water.