Enhanced Visible-Light Degradation of Rhodamine B by Hydrothermally Synthesized WO3@g‑C3N4 Heterostructures for Water Remediation

Abstract Graphitic carbon nitride (g-C3N4) is a polymeric semiconductor that has garnered considerable attention in photocatalysis due to its high activity in processes such as the degradation of organic pollutants, water splitting, and CO2 reduction. Tungsten trioxide (WO3), a metal oxide semiconductor known for its electrochromic, photochromic, and photocatalytic properties, has shown strong potential for coupling with g-C3N4 to enhance visible-light-driven photocatalytic performance. This study investigates the effect of varying WO3 content (0%, 3%, 5%, 7%, 9%) on the structural and photocatalytic properties of WO3@ g-C3N4 composites for Rhodamine B (RhB) degradation under visible light irradiation. The composites were synthesized via a hydrothermal method and characterized using XRD, FTIR, SEM, TEM, DRS, and PL analyses to evaluate their crystal structure, chemical bonding, surface morphology, band gap energy, and charge carrier dynamics. The results show that increasing WO3 content modifies the band structure and enhances charge separation efficiency. Photocatalytic tests demonstrated a progressive increase in RhB degradation efficiency with higher WO3 content, reaching a maximum of 99.7% after 210 min at 9% loading. The catalytic activity was only slightly affected by pH and the presence of reactive species scavengers. The enhanced performance of the 9% WO3@g-C3N4 composite is attributed to improved visible light absorption and reduced electron–hole recombination.