Construction of C3N4/CdS nanojunctions on carbon fiber cloth as a filter-membrane-shaped photocatalyst for degrading flowing wastewater

Highlights: • The growth of C₃N₄/CdS heterojunctions on carbon-fiber (CF) cloth has been realized. • CF/C₃N₄/CdS cloth exhibits excellent flexibility and broad visible light-responsive photocatalytic activity. • CF/C₃N₄/CdS cloth can be used as filter-membrane for degrading and mineralizing contaminant from flowing wastewater. • The dominant active species are h⁺ and .• OH. • CF/C₃N₄/CdS cloth can be easily recycled and remains good stability. -- Abstract: Photocatalysis has become an exciting and energy-saving technology for wastewater purification, but its practical applications have been limited by the difficulty involved in obtaining efficient and easily recyclable macroscale photocatalysts. Herein, we report the construction of C₃N₄/CdS nanojunctions on carbon fiber (CF) cloth as a filter-membrane-shaped photocatalyst. CF/C₃N₄/CdS cloth exhibits enhanced photoabsorption and photocurrent. Under visible light irradiation, CF/C₃N₄/CdS cloth shows improved photocatalytic activity for different pollutants (99% methylene blue (MB), 98% acid orange 7 (AO7), 81% tetracycline (TC), 81% Cr(VI)), compared with CF/C₃N₄ cloth (99% MB, 74% AO7, 48% TC, 20% Cr(VI)) and CF/CdS cloth (35% MB, 10% AO7, 47% TC, 48% Cr(VI)). Furthermore, with CF/C₃N₄/CdS cloth as a filter-membrane-shaped photocatalyst, the removal rate for TC and Cr(VI) was found to increase up to 73% and 83% after a 6 grade reaction, respectively, higher than that obtained for CF/C₃N₄ cloth (52% TC, 22% Cr(VI)) or CF/CdS cloth (50% TC, 42% Cr(VI)). The improved photocatalytic activity of CF/C₃N₄/CdS cloth results from the construction of C₃N₄/CdS nanojunctions, which not only confers stronger photoabsorption but also results in the efficient separation of photogenerated electron-hole pairs. In particular, several possible pathways for TC degradation were proposed based on the intermediate products formed. Therefore, CF/C₃N₄/CdS cloth can act as an efficient and recyclable filter-membrane-shaped photocatalyst for dealing with flowing wastewater, and it also provides new perspectives for the development of flexible macroscale photocatalysts.