Boosted Visible‐Light Photocatalytic Reduction of Cr (VI) via Plasmonic Ag‐TiO2 Nanocomposite

ABSTRACT Ag‐TiO 2 nanocomposites containing 1, 3, and 5 wt.% Ag was synthesized via a precipitation‐assisted sol‐gel process followed by chemical reduction and evaluated for visible‐light‐driven reduction of Cr(VI). Structural, morphological, surface chemical, and optical properties were characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), UV‐visible diffuse reflectance spectroscopy (UV‐DRS), and photoluminescence (PL) spectroscopy. The formation of anatase TiO 2 decorated with well‐dispersed metallic Ag nanoparticles was confirmed. Among all samples, 3 wt.% Ag‐TiO 2 (AT‐3) exhibited the highest photocatalytic activity, achieving 99.3% Cr(VI) reduction within 120 min under visible‐light irradiation at pH 4. The enhanced performance is attributed to localized surface plasmon resonance (SPR)‐induced visible‐light absorption, efficient interfacial charge separation, and reduced electron‐hole recombination. UV‐DRS analysis showed a decrease in the apparent band‐gap energy from 3.44 eV (TiO 2 ) to 3.12 eV (AT‐3), which is mainly attributed to SPR and interfacial charge transfer rather than to lattice modification. PL results confirmed suppressed recombination of charge carriers. The hierarchical macro‐mesoporous fibrous structure further enhanced mass transport and surface accessibility. These findings demonstrate the potential of plasmonic Ag‐TiO 2 photocatalysts for efficient solar‐driven remediation of Cr(VI) in wastewater treatment.