Bi2O2CO3–Bi2O2(OH)NO3/g-C3N4 heterojunction as a visible-light-driven photocatalyst with enhanced photogenerated charge separation

Abstract

Constructing heterojunction to achieve efficient charge separation and transfer is a significant way to enhance photocatalytic activity. Herein, a novel ternary Bi2O2CO3–Bi2O2(OH)NO3/g-C3N4 (labeled as BOC-BON/CN) heterojunction photocatalyst was successfully synthesized by ion exchange reaction under hydrothermal conditions. The products were characterized by various analytical methods, including X-ray diffraction (XRD), Fourier transform-infrared spectrometer (FT-IR), X-ray photoelectron spectroscopy (XPS), X-ray spectrometer (SEM), UV–vis reflectance spectra (UV–vis DRS), photoluminescence (PL), photocurrent response and electrochemical impedance spectroscopy (EIS). Heterojunction formation mechanism and photocatalytic degradation mechanism were discussed in detail. The prepared BOC-BON/CN heterojunction exhibited excellent Rhodamine B (RhB) photodegradation rate of 0.0476 min−1 under visible light, which was 3.55 times of the pristine g-C3N4 (0.0134 min−1). The significant increase in photodegradation rate was attributable to the heterojunction structure, which promotes the separation of photogenerated charges. Bi2O2(OH)NO3 played an essential role as electron accelerator in the charge transfer process. The internal electric field of Bi2O2(OH)NO3 accelerates the directed transfer of electron from g-C3N4 to Bi2O2CO3. This work extends the study of g–C3N4–based photocatalytic systems and demonstrates Bi2O2(OH)NO3 as a promising cocatalyst.