The study reports the fabrication of a 2D/3D n-CIS/o-CIS S-scheme homojunction photocatalyst by adjusting the amount of polyvinyl pyrrolidone (PVP) during the solvothermal synthesis. This homojunction, composed of 2D CdIn₂S₄ nanosheets coated on 3D CdIn₂S₄ octahedra, is characterized using various techniques to investigate the formation of an internal electric field that facilitates the separation and migration of photogenerated electron-hole pairs. The n-CIS/o-CIS composite exhibits significantly improved photocatalytic activity and stability in the selective oxidation of phenylcarbinol (PhCH₂OH) to benzaldehyde (PhCHO) under visible light irradiation compared to pure n-CIS and o-CIS samples. The enhanced performance is attributed to the S-scheme charge transfer mechanism, which retains photoexcited electrons with high reduction potential and holes with strong oxidation potential, leading to efficient redox reactions. The study contributes novel insights into the development of metal sulfide S-scheme homojunction photocatalysts for solar energy conversion.The study reports the fabrication of a 2D/3D n-CIS/o-CIS S-scheme homojunction photocatalyst by adjusting the amount of polyvinyl pyrrolidone (PVP) during the solvothermal synthesis. This homojunction, composed of 2D CdIn₂S₄ nanosheets coated on 3D CdIn₂S₄ octahedra, is characterized using various techniques to investigate the formation of an internal electric field that facilitates the separation and migration of photogenerated electron-hole pairs. The n-CIS/o-CIS composite exhibits significantly improved photocatalytic activity and stability in the selective oxidation of phenylcarbinol (PhCH₂OH) to benzaldehyde (PhCHO) under visible light irradiation compared to pure n-CIS and o-CIS samples. The enhanced performance is attributed to the S-scheme charge transfer mechanism, which retains photoexcited electrons with high reduction potential and holes with strong oxidation potential, leading to efficient redox reactions. The study contributes novel insights into the development of metal sulfide S-scheme homojunction photocatalysts for solar energy conversion.