A polymer solution containing 0.5 wt.% polydiallyl dimethyl ammonium chloride was used to modify graphitic carbon nitride by the sol-carbonization method (PDDA (0.5) @ g-C3N4). Titanium dioxide nanoparticles were synthesized by microwave irradiation followed by hydrothermal treatment to obtain titanium nanowires (TiNWs). The TiO2NWs/ (PDDA (0.5) @g-C3N4) nanocomposite was prepared with different wt. % of TiO2NWs to (PDDA (0.5) @g-C3N4), 50:50, and 30:70 by the wet impregnation method. The prepared nanocomposites were applied in twin applications: photo-catalysis and quantum dot solar cells. Basic blue (Bb) and Methyl Orange (MO) were used as pollutants, and the degradation efficiencies were 96, 94, 90.8, 63.7, and 30.7% for TiO2NWs/ (PDDA (0.5) @g-C3N4) (50:50), TiO2NWs/ (PDDA (0.5) @g-C3N4) (30:70), TiO2NWs, g-C3N4, and (PDDA (0.5) @ g-C3N4), respectively, compared with the control experiment (without catalyst) at 14.8%. A perceived improvement in photovoltaic performance of TiO2NWs/ (PDDA (0.5) @g-C3N4) (50:50) was observed. A conversion efficiency of 2.8% with a VoC of 504 mV, JSC of 9.92 mA cm-2, and a fill factor (FF) of 0.58 was achieved using 7 layers of CdS QD by the SILAR method.