MnOx/g-C₃N₄ heterostructure Modified Pervious Concrete for Enhanced Visible-Light Photocatalytic Degradation of Rhodamine B

Abstract Graphitic carbon nitride (g-C₃N₄) represents a promising metal-free visible-light-responsive photocatalyst for organic wastewater remediation. However, rapid recombination of photogenerated carriers and inadequate visible-light harvesting severely limit its practical environmental applications. Herein, MnOₓ/g-C₃N₄ heterostructured composites were fabricated by a one-step thermal method to promote charge separation and enhance visible-light utilization. The photocatalytic activity of the catalysts was further assessed by degradation of Rhodamine B (RhB) under visible-light irradiation. The optimized Mn-GCN 700-3:2 achieved 99.83% RhB degradation within 60 min, 49.51% higher than pristine GCN 700 , which showed 75.57% degradation after 120 min, and retained 90.13% efficiency after six cycles. All the samples were subjected to comprehensive characterizations (XRD, XPS, SEM, TEM, FT-IR, UV-vis DRS and PL). XPS analysis revealed that Mn 3+ accounted for 70% of the Mn species, forming a mixed-valence Mn 3+ /Mn 4+ system, while FT-IR confirmed strong interfacial coupling between MnO x and g-C 3 N 4 . UV-vis DRS, bandgap, and PL analyses demonstrated that Mn incorporation markedly narrowed the bandgap, enhanced visible-light absorption, and suppressed charge recombination. The Mn 3+ /Mn 4+ redox cycle acted as electron traps to promote charge separation and O 2 activation into ·O 2 - , which cooperated with ·OH and h + to drive efficient RhB degradation. When immobilized on pervious concrete at 5 g/L (MnPC), the degradation of RhB achieved 78.11% within 120 min under visible light, outperforming GPC and satisfying the Technical Specification for Pervious Cement Concrete Pavement . This work proposes a facile route to synthesize high-efficiency photocatalysts and spray on pervious concrete, which provides a sustainable technical candidate for decentralized urban stormwater and wastewater purification.