Tandem PEC Device with Perovskite/g-C₃N₄ and Phosphorene/g-C₃N₄ as the Electrodes for Hydrogen Evolution and Ciprofloxacin Photodegradation

The improvement and development of technology and alternative energy have been the main goals of human civilization and industrialization. Meanwhile, the environmental pollution caused by over-development has also increased. Hence, much attention has been attached to research on the removal of pollutants from water bodies and the development of low-carbon green energy. Perovskite (ABX₃) is a novel nanomaterial with energy storage, tunable structure, and visible-light-responsive properties, which has been widely utilized in supercapacitors and photocatalysis fields. But the traditional perovskite can cause possible pollution problems in the environment because of the toxic metal that exists in the B-site ions. Phosphorene is another optical 2-dimensional nanomaterial with optical/electronic properties that have been successfully utilized in photocatalysis and photoelectrochemistry. Nevertheless, the high recombination rate decreases the photo-activity of base photocatalysts. Therefore, the combination of carbon-based photocatalyst of graphitic carbon nitride (g-C₃N₄) with perovskite and phosphorene can not only extend the absorption efficiency of visible light but also decrease the recombination rates of e^--h⁺ pairs. In this study, we have synthesized promising TAB₃Bi₂Br₇I₂/C₃N₄ (ABI/CN) and phosphorene/C₃N₄ (P/CN) for photoelectrochemically enhanced antibiotic removal efficiency and H₂ evolution from water splitting, respectively, under the solar light irradiation. The 1-D C₃N₄ nanofiber in composite, prepared by electrospinning method, increases the specific surface area and electron mobility, while the existence of TAB₃Bi₂Br₇I₂ perovskite, synthesized via the solvothermal method, replaces the original structure by utilizing the Bi element to reduce the possible environmental problems. Together, they form the Z-scheme structure as a photoanode to increase the photoresponsiveness. On the other hand, the 2-D phosphorene, which fabricated via exfoliation method, decorated onto the 1-D C₃N₄as a p-n junction-based photocathode enhances the absorption wavelength from 456 to 476–644 nm to decrease the e^--h⁺ recombination rates in tandem PEC device. These Z-scheme and p-n heterojunction photocatalysts exhibit excellent visible-light photocatalytic efficiency with electrochemical CIP degradation achieved to 80% in 30 min and H₂ generation of 1.2 mmol h^-1 g^-1, which are higher than base photocatalysts under the same conditions. Results have indicated that ABI/CN and P/CN nanophotocatalysts are effective photo-responsive nanomaterials to enhance the e^--h⁺ separation for pollutant destruction and H₂ evolution from water splitting, which can open a new chapter for the fabrication of photoelectrochemical catalysts with suitable morphology for a wide variety of green and sustainable technologies.