This study focuses on developing a g-C 3 N 4 /Sb 2 S 3 heterojunction photocatalyst with different g-C 3 N 4 to Sb 2 S 3 weight ratios (1:1, 1:3, and 3:1) for degrading tetracycline (TC) pollutants. The 1:3 ratio (13 GS) exhibited optimal photocatalytic performance, achieving 99% TC degradation under sunlight within 120 min, compared to 78.4% under visible light and 38% under UV light. The 13 GS catalyst demonstrated strong reusability, maintaining 80% degradation efficiency after six cycles. Scavenger experiments identified hydroxyl radicals as crucial for TC degradation, with DMSO reducing activity by 30%. The photocatalyst also showed high hydrogen production with an apparent quantum efficiency (AQE) of 19.8% under standard conditions, and improved AQE in acidic (23%) and basic (22.7%) conditions, and with CH 3 OH (23.2%). This g-C 3 N 4 /Sb 2 S 3 heterojunction offers a promising solution for degrading toxic contaminants and has the potential for solar-powered applications.