BiOCl anchored porous g-C3N4 S-scheme heterojunction with enhanced bifunctional photocatalytic performance for RhB degradation and Cr(VI) reduction

The practical implementation of semiconductor photocatalysis is often impeded by three key challenges: restricted light absorption, rapid recombination of photogenerated charge carriers, and inadequate stability in complex aqueous environments. In this work, a g-C3N4/BiOCl heterojunction photocatalyst was successfully fabricated. The synergistic effects of its porous structure, oxygen vacancies, and Bi–N bonds significantly boost the photocatalytic performance. Photoelectrochemical analyses reveal that the heterojunction not only extends the optical absorption edge to the visible region but also enhances the photocurrent response and reduces charge transfer resistance, leading to efficient separation and transport of photogenerated carriers. Under irradiation with a 300 W xenon lamp equipped with a 420 nm cutoff filter, the g-C3N4/BiOCl heterojunction exhibited significantly enhanced photocatalytic activity in the degradation of Rhodamine B (RhB) and reduction of hexavalent chromium (Cr(VI)) relative to pristine g-C3N4 and BiOCl. Notably, the g-C3N4/BiOCl-2 sample achieved 99.12% removal of 20 mg/L Cr(VI) within 25 minutes, with a reaction rate constant of 0.10098 min-1—1.88-fold and 2.72-fold higher than those of pristine BiOCl and g-C3N4, respectively.Environmental adaptability studies revealed that this heterojunction exhibited optimal Cr(VI) reduction performance under acidic conditions (pH=3). Its photocatalytic reduction efficiencies in deionized water, tap water, river water, and industrial wastewater were 97%, 87.6%, 81.4%, and 73.1%, respectively, highlighting its strong practical applicability in diverse aqueous environments.. Common ion influence experiments further confirmed that NH4+ promotes the reduction process, while CO32− and PO43− inhibit the reaction due to the alkaline environment generated by hydrolysis. Cl−, SO42−, and Ca2+ had negligible effects. Cycling tests revealed that g-C3N4/BiOCl-2 maintained over 85% photocatalytic activity after five cycles, exhibiting superior durability compared to pure g-C3N4 (11.1%) and BiOCl (39.7%). This work enhance the photocatalytic reduction of heavy metals in complex aqueous environments through the construction of a highly efficient and stable Z-scheme heterojunction photocatalyst, thereby offering theoretical and experimental foundations for the degradation of industrial dye pollutants.