ZnO/NiO coaxial heterojunction nanofibers with oxygen vacancies for efficient photocatalytic Congo red degradation and hydrogen peroxide production

Abstract

Vacancy engineering is a highly efficient approach to enhancing photocatalytic activity. This research presents an innovative development of ZnO/NiO coaxial heterojunction nanofibers (ZN1/1) and ZnO/NiO coaxial heterojunction nanofibers with engineered oxygen vacancies (OVs-ZN1/1) via electrospinning and annealing. Detailed characterization of the nanofiber microstructure was conducted using scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The OVs-ZN1/1 nanofibers demonstrated outstanding and unprecedented photocatalytic performance, achieving a 99 % degradation rate of Congo red dye (CR) under simulated solar light in just 45 min, with a good degradation coefficient of 0.091 min−1. Remarkably, the nanofibers’ photocatalytic activity remained a high level even after five cycles. Moreover, the photocatalytic H2O2 yield of OVs-ZN1/1 increased 20 times as much as that of ZN1/1. Experiments and mechanism analysis indicate that oxygen vacancy, as the electron trapping site of photoexcitation, accelerates the charge separation and transfer at the interface, thus promoting the adsorption and activation of target molecules. This study highlights the novel and superior performance of photochemical catalysts achieved through the strategic incorporation of oxygen vacancies and heterojunctions.