Enhanced ammonium degradation via functionalized photocatalysts: metal − polyvinylpyrrolidone coated TiO2 with improved electrochemical and band gap properties

• TiO 2 photocatalysts were functionalized with polyvinylpyrrolidone (PVP) and transition metals, including Fe, Cu, and Co. • Cu-PVP-coated TiO 2 (Cu-p-TiO 2 ) demonstrated superior electrical conductivity and photocatalytic performance. • Under UV light, Cu-p-TiO 2 achieved 84.9 % ammonium degradation, outperforming Fe-p-TiO 2 (49.7 %) and Co-p-TiO 2 (64.2 %). Novel photocatalysts were successfully synthesized by functionalizing titanium dioxide (TiO 2 ) with polyvinylpyrrolidone (PVP) and transition metals (Fe, Cu, and Co) through a combined polymerization and metal coordination process (metal-p-TiO 2 ). In terms of photocatalytic performance, Cu-p-TiO 2 demonstrated a significantly higher ammonium degradation efficiency of 84.9 % compared to commercial TiO 2 (60.6 %) in 100 mg L −1 ammonium solutions. Cu-p-TiO 2 also exhibited 1.71-fold and 1.32-fold higher degradation efficiencies than Fe-p-TiO 2 (49.7 %) and Co-p-TiO 2 (64.2 %), respectively. The electrochemical studies revealed that Cu-p-TiO 2 exhibited higher electrical conductivity (9.16 × 10 −7 S cm −1 ) than Fe-p-TiO 2 (1.23 × 10 −7 S cm −1 ) and Co-p-TiO 2 (1.21 × 10 −7 S cm −1 ), indicating that it offers more efficient electron transport for ammonium degradation. Additionally, Cu-p-TiO 2 displayed a significantly lower energy gap (1.98 eV) than Co-p-TiO 2 (3.30 eV) and Fe-p-TiO 2 (3.21 eV), which is consistent with its superior electrical conductivity. These electrochemical properties contributed to the enhanced photocatalytic efficiency of Cu-p-TiO 2 .