Photocatalysis has emerged as a sustainable and efficient approach for addressing environmental challenges, particularly in wastewater treatment and energy applications. This study reports the fabrication and performance evaluation of In₂S₃-based photocatalytic hydrogels engineered for dual applications in environmental remediation and oxidative energy generation. Three hydrogel systems&mdashIn₂S₃-TA, ICS, and ICB&mdashwere synthesized via hydrothermal and crosslinking methods using biopolymer supports (alginate, pectin or CMC) to improve structural stability, dispersion, and reusability. The In₂S₃-TA hydrogel, exhibiting a flower-like morphology, showed enhanced visible-light absorption and reduced band gap (~1.4 eV) as confirmed by XRD, FTIR, PL, and UV-DRS analysis. It achieved 81% degradation of sulfamethoxazole (SMX, 10 mg/L) in 60 minutes and maintained 63% efficiency after 8 reuse cycles. The binary ICS hydrogel, comprising a type-II heterojunction of In₂S₃ nanorods and CuSe nanoflowers embedded in a 3D CMC matrix, was validated through XRD, FTIR, XPS, FESEM/EDX, and electrochemical studies. It showed strong visible-light activity with a 1.4 eV band gap, achieving 100% SMX degradation in 5 minutes (rate constant 0.989 min⁻¹), 34.5% dark adsorption, and retained 92% activity after 20 cycles. The ternary ICB hydrogel, integrating In₂S₃, CdS, and Bi₂WO₆ into an alginate network, formed a dual Z-scheme heterojunction with spherical, microporous structure confirmed by XRD, FTIR, EDX mapping, PL, Mott-Schottky, and EIS. It achieved 99% SMX degradation in 20 minutes (rate constant 0.191 min⁻¹), generated 455 &muM H₂O₂ with isopropanol, and maintained 87% efficiency over 10 cycles, even under solar irradiation and in real water matrices. Mechanistic studies revealed the formation of reactive species (&bullOH, SO₄&bull⁻, &bullO₂⁻) and complete SMX mineralization. This study highlights the potential of In₂S₃-based hydrogels as multifunctional photocatalysts, capable of addressing wastewater pollution and contributing to energy applications through visible light-driven processes.

Keywords: Photocatalysis, In₂S₃, Hydrogel, Wastewater treatment, Sulfamethoxazole, Energy applications.