Optimization of Intercalated 2D BiOCl Sheets into Bi2WO6 Flowers for Photocatalytic NH3 Production and Antibiotic Pollutant Degradation

Photocatalytic N₂ fixation is a complex reaction, thereby prompting researchers to design and analyze highly efficient materials. Herein, one-pot hydrothermal Bi₂WO₆-BiOCl (BW-BiOCl) heterojunctions were synthesized by varying the molar ratio of tungsten: chlorine precursor. Major morphological transformations in BiOCl were observed wherein it turned from thick sheets ∼230 nm in pure BiOCl to ∼30 nm in BW-BiOCl. This was accompanied by extensive growth of {001} facets verified from X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) analyses. A p-n heterojunction was formed between Bi₂WO₆ and BiOCl evidenced via photoluminescence (PL), time-resolved photoluminescence (TRPL), photocurrent response, and electrochemical impedance spectroscopy (EIS) analyses. The formation of heterojunction between Bi₂WO₆ and BiOCl led to the reduction of the work function in the BW-BiOCl 0.25 hybrid confirmed via ultraviolet photoelectron spectroscopy (UPS) analysis. BW-BiOCl 0.25 could produce ammonia up to 345.1 μmol·L^-1·h^-1 owing to the formation of a robust heterojunction with an S-scheme carrier transport mechanism. Recycle tests resulted in no loss in N₂ reduction activities with post-catalytic analysis, showcasing the high stability of the synthesized heterojunction. Novel performance was owed to its excellent chemisorption of N₂ gas on the heterojunction surface verified by N₂-temperature programmed desorption (TPD). BW-BiOCl 0.25 also displayed a superior rate constant of 3.03 × 10^-2 min^-1 for 90 min CIP degradation time, higher than pristine BiOCl and Bi₂WO₆. Post-photocatalytic Fourier transform infrared (FTIR) spectroscopy of BW-BiOCl 0.25 revealed the presence of C-H stretching peaks in the range of 2850-2960 cm^-1 due to adsorbed CIP and methanol species in CIP degradation and N₂ fixation, respectively. This also confirmed the enhanced adsorption of reacting species onto the heterojunction surface.